Hi,
The "track FOLL_PIN pages" would have been the very next patch, but it is not included here because I'm still debugging a bug report from Leon. Let's get all of the prerequisite work (it's been reviewed) into the tree so that future reviews are easier. It's clear that any fixes that are required to the tracking patch, won't affect these patches here.
This implements an API naming change (put_user_page*() --> unpin_user_page*()), and also adds FOLL_PIN page support, up to *but not including* actually tracking FOLL_PIN pages. It extends the FOLL_PIN support to a few select subsystems. More subsystems will be added in follow up work.
Christoph Hellwig, a point of interest:
a) I've moved the bulk of the code out of the inline functions, as requested, for the devmap changes (patch 4: "mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages").
Changes since v11: Fixes resulting from Kirill Shutemov's review, plus a fix for a kbuild robot-reported warning.
* Only include the first 22 patches: up to, but not including, the "track FOLL_PIN pages" patch.
* Improved the efficiency of put_compound_head(), by avoiding get_page() entirely, and instead doing the mass subtraction on one less than refs, followed by a final put_page().
* Got rid of the forward declaration of __gup_longterm_locked(), by moving get_user_pages_remote() further down in gup.c
* Got rid of a redundant page_is_devmap_managed() call, and simplified put_devmap_managed_page() as part of that small cleanup.
* Changed put_devmap_managed_page() to do an early out if the page is not devmap managed. This saves an indentation level.
* Applied the same type of change to __unpin_devmap_managed_user_page(), which has the same checks.
* Changed release_pages() to handle the changed put_devmap_managed_page() API.
* Removed EXPORT_SYMBOL(free_devmap_managed_page), as it is not required, after the other refactoring.
* Fixed a kbuild robot sparse warning: added "static" to try_pin_compound_head()'s declaration.
There is a git repo and branch, for convenience:
git@github.com:johnhubbard/linux.git pin_user_pages_tracking_v8
For the remaining list of "changes since version N", those are all in v11, which is here:
https://lore.kernel.org/r/20191216222537.491123-1-jhubbard@nvidia.com
============================================================ Overview:
This is a prerequisite to solving the problem of proper interactions between file-backed pages, and [R]DMA activities, as discussed in [1], [2], [3], and in a remarkable number of email threads since about 2017. :)
A new internal gup flag, FOLL_PIN is introduced, and thoroughly documented in the last patch's Documentation/vm/pin_user_pages.rst.
I believe that this will provide a good starting point for doing the layout lease work that Ira Weiny has been working on. That's because these new wrapper functions provide a clean, constrained, systematically named set of functionality that, again, is required in order to even know if a page is "dma-pinned".
In contrast to earlier approaches, the page tracking can be incrementally applied to the kernel call sites that, until now, have been simply calling get_user_pages() ("gup"). In other words, opt-in by changing from this:
get_user_pages() (sets FOLL_GET) put_page()
to this: pin_user_pages() (sets FOLL_PIN) unpin_user_page()
============================================================ Testing:
* I've done some overall kernel testing (LTP, and a few other goodies), and some directed testing to exercise some of the changes. And as you can see, gup_benchmark is enhanced to exercise this. Basically, I've been able to runtime test the core get_user_pages() and pin_user_pages() and related routines, but not so much on several of the call sites--but those are generally just a couple of lines changed, each.
Not much of the kernel is actually using this, which on one hand reduces risk quite a lot. But on the other hand, testing coverage is low. So I'd love it if, in particular, the Infiniband and PowerPC folks could do a smoke test of this series for me.
Runtime testing for the call sites so far is pretty light:
* io_uring: Some directed tests from liburing exercise this, and they pass. * process_vm_access.c: A small directed test passes. * gup_benchmark: the enhanced version hits the new gup.c code, and passes. * infiniband: Ran rdma-core tests: rdma-core/build/bin/run_tests.py * VFIO: compiles (I'm vowing to set up a run time test soon, but it's not ready just yet) * powerpc: it compiles... * drm/via: compiles... * goldfish: compiles... * net/xdp: compiles... * media/v4l2: compiles...
[1] Some slow progress on get_user_pages() (Apr 2, 2019): https://lwn.net/Articles/784574/ [2] DMA and get_user_pages() (LPC: Dec 12, 2018): https://lwn.net/Articles/774411/ [3] The trouble with get_user_pages() (Apr 30, 2018): https://lwn.net/Articles/753027/
Dan Williams (1): mm: Cleanup __put_devmap_managed_page() vs ->page_free()
John Hubbard (21): mm/gup: factor out duplicate code from four routines mm/gup: move try_get_compound_head() to top, fix minor issues mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages goldish_pipe: rename local pin_user_pages() routine mm: fix get_user_pages_remote()'s handling of FOLL_LONGTERM vfio: fix FOLL_LONGTERM use, simplify get_user_pages_remote() call mm/gup: allow FOLL_FORCE for get_user_pages_fast() IB/umem: use get_user_pages_fast() to pin DMA pages media/v4l2-core: set pages dirty upon releasing DMA buffers mm/gup: introduce pin_user_pages*() and FOLL_PIN goldish_pipe: convert to pin_user_pages() and put_user_page() IB/{core,hw,umem}: set FOLL_PIN via pin_user_pages*(), fix up ODP mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() drm/via: set FOLL_PIN via pin_user_pages_fast() fs/io_uring: set FOLL_PIN via pin_user_pages() net/xdp: set FOLL_PIN via pin_user_pages() media/v4l2-core: pin_user_pages (FOLL_PIN) and put_user_page() conversion vfio, mm: pin_user_pages (FOLL_PIN) and put_user_page() conversion powerpc: book3s64: convert to pin_user_pages() and put_user_page() mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" mm, tree-wide: rename put_user_page*() to unpin_user_page*()
Documentation/core-api/index.rst | 1 + Documentation/core-api/pin_user_pages.rst | 232 +++++++++ arch/powerpc/mm/book3s64/iommu_api.c | 10 +- drivers/gpu/drm/via/via_dmablit.c | 6 +- drivers/infiniband/core/umem.c | 19 +- drivers/infiniband/core/umem_odp.c | 13 +- drivers/infiniband/hw/hfi1/user_pages.c | 4 +- drivers/infiniband/hw/mthca/mthca_memfree.c | 8 +- drivers/infiniband/hw/qib/qib_user_pages.c | 4 +- drivers/infiniband/hw/qib/qib_user_sdma.c | 8 +- drivers/infiniband/hw/usnic/usnic_uiom.c | 4 +- drivers/infiniband/sw/siw/siw_mem.c | 4 +- drivers/media/v4l2-core/videobuf-dma-sg.c | 8 +- drivers/nvdimm/pmem.c | 6 - drivers/platform/goldfish/goldfish_pipe.c | 35 +- drivers/vfio/vfio_iommu_type1.c | 35 +- fs/io_uring.c | 6 +- include/linux/mm.h | 95 +++- mm/gup.c | 495 ++++++++++++-------- mm/gup_benchmark.c | 9 +- mm/memremap.c | 75 ++- mm/process_vm_access.c | 28 +- mm/swap.c | 27 +- net/xdp/xdp_umem.c | 4 +- tools/testing/selftests/vm/gup_benchmark.c | 6 +- 25 files changed, 762 insertions(+), 380 deletions(-) create mode 100644 Documentation/core-api/pin_user_pages.rst
There are four locations in gup.c that have a fair amount of code duplication. This means that changing one requires making the same changes in four places, not to mention reading the same code four times, and wondering if there are subtle differences.
Factor out the common code into static functions, thus reducing the overall line count and the code's complexity.
Also, take the opportunity to slightly improve the efficiency of the error cases, by doing a mass subtraction of the refcount, surrounded by get_page()/put_page().
Also, further simplify (slightly), by waiting until the the successful end of each routine, to increment *nr.
Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Jérôme Glisse jglisse@redhat.com Reviewed-by: Jan Kara jack@suse.cz Cc: Kirill A. Shutemov kirill@shutemov.name Cc: Ira Weiny ira.weiny@intel.com Cc: Christoph Hellwig hch@lst.de Cc: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- mm/gup.c | 95 ++++++++++++++++++++++++-------------------------------- 1 file changed, 40 insertions(+), 55 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index 7646bf993b25..d56c6d6b85d3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1978,6 +1978,29 @@ static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr, } #endif
+static int record_subpages(struct page *page, unsigned long addr, + unsigned long end, struct page **pages) +{ + int nr; + + for (nr = 0; addr != end; addr += PAGE_SIZE) + pages[nr++] = page++; + + return nr; +} + +static void put_compound_head(struct page *page, int refs) +{ + VM_BUG_ON_PAGE(page_ref_count(page) < refs, page); + /* + * Calling put_page() for each ref is unnecessarily slow. Only the last + * ref needs a put_page(). + */ + if (refs > 1) + page_ref_sub(page, refs - 1); + put_page(page); +} + #ifdef CONFIG_ARCH_HAS_HUGEPD static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end, unsigned long sz) @@ -2007,32 +2030,20 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, /* hugepages are never "special" */ VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
- refs = 0; head = pte_page(pte); - page = head + ((addr & (sz-1)) >> PAGE_SHIFT); - do { - VM_BUG_ON(compound_head(page) != head); - pages[*nr] = page; - (*nr)++; - page++; - refs++; - } while (addr += PAGE_SIZE, addr != end); + refs = record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(head, refs); - if (!head) { - *nr -= refs; + if (!head) return 0; - }
if (unlikely(pte_val(pte) != pte_val(*ptep))) { - /* Could be optimized better */ - *nr -= refs; - while (refs--) - put_page(head); + put_compound_head(head, refs); return 0; }
+ *nr += refs; SetPageReferenced(head); return 1; } @@ -2079,28 +2090,19 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr); }
- refs = 0; page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); - do { - pages[*nr] = page; - (*nr)++; - page++; - refs++; - } while (addr += PAGE_SIZE, addr != end); + refs = record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pmd_page(orig), refs); - if (!head) { - *nr -= refs; + if (!head) return 0; - }
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { - *nr -= refs; - while (refs--) - put_page(head); + put_compound_head(head, refs); return 0; }
+ *nr += refs; SetPageReferenced(head); return 1; } @@ -2120,28 +2122,19 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr); }
- refs = 0; page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); - do { - pages[*nr] = page; - (*nr)++; - page++; - refs++; - } while (addr += PAGE_SIZE, addr != end); + refs = record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pud_page(orig), refs); - if (!head) { - *nr -= refs; + if (!head) return 0; - }
if (unlikely(pud_val(orig) != pud_val(*pudp))) { - *nr -= refs; - while (refs--) - put_page(head); + put_compound_head(head, refs); return 0; }
+ *nr += refs; SetPageReferenced(head); return 1; } @@ -2157,28 +2150,20 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, return 0;
BUILD_BUG_ON(pgd_devmap(orig)); - refs = 0; + page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); - do { - pages[*nr] = page; - (*nr)++; - page++; - refs++; - } while (addr += PAGE_SIZE, addr != end); + refs = record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pgd_page(orig), refs); - if (!head) { - *nr -= refs; + if (!head) return 0; - }
if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { - *nr -= refs; - while (refs--) - put_page(head); + put_compound_head(head, refs); return 0; }
+ *nr += refs; SetPageReferenced(head); return 1; }
An upcoming patch uses try_get_compound_head() more widely, so move it to the top of gup.c.
Also fix a tiny spelling error and a checkpatch.pl warning.
Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- mm/gup.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index d56c6d6b85d3..5938e29a5a8b 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -29,6 +29,21 @@ struct follow_page_context { unsigned int page_mask; };
+/* + * Return the compound head page with ref appropriately incremented, + * or NULL if that failed. + */ +static inline struct page *try_get_compound_head(struct page *page, int refs) +{ + struct page *head = compound_head(page); + + if (WARN_ON_ONCE(page_ref_count(head) < 0)) + return NULL; + if (unlikely(!page_cache_add_speculative(head, refs))) + return NULL; + return head; +} + /** * put_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages * @pages: array of pages to be maybe marked dirty, and definitely released. @@ -1807,20 +1822,6 @@ static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start, } }
-/* - * Return the compund head page with ref appropriately incremented, - * or NULL if that failed. - */ -static inline struct page *try_get_compound_head(struct page *page, int refs) -{ - struct page *head = compound_head(page); - if (WARN_ON_ONCE(page_ref_count(head) < 0)) - return NULL; - if (unlikely(!page_cache_add_speculative(head, refs))) - return NULL; - return head; -} - #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, unsigned int flags, struct page **pages, int *nr)
From: Dan Williams dan.j.williams@intel.com
After the removal of the device-public infrastructure there are only 2 ->page_free() call backs in the kernel. One of those is a device-private callback in the nouveau driver, the other is a generic wakeup needed in the DAX case. In the hopes that all ->page_free() callbacks can be migrated to common core kernel functionality, move the device-private specific actions in __put_devmap_managed_page() under the is_device_private_page() conditional, including the ->page_free() callback. For the other page types just open-code the generic wakeup.
Yes, the wakeup is only needed in the MEMORY_DEVICE_FSDAX case, but it does no harm in the MEMORY_DEVICE_DEVDAX and MEMORY_DEVICE_PCI_P2PDMA case.
Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Jérôme Glisse jglisse@redhat.com Cc: Jan Kara jack@suse.cz Cc: Ira Weiny ira.weiny@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/nvdimm/pmem.c | 6 ---- mm/memremap.c | 80 ++++++++++++++++++++++++------------------- 2 files changed, 44 insertions(+), 42 deletions(-)
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index ad8e4df1282b..4eae441f86c9 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -337,13 +337,7 @@ static void pmem_release_disk(void *__pmem) put_disk(pmem->disk); }
-static void pmem_pagemap_page_free(struct page *page) -{ - wake_up_var(&page->_refcount); -} - static const struct dev_pagemap_ops fsdax_pagemap_ops = { - .page_free = pmem_pagemap_page_free, .kill = pmem_pagemap_kill, .cleanup = pmem_pagemap_cleanup, }; diff --git a/mm/memremap.c b/mm/memremap.c index c51c6bd2fe34..f915d074ac20 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -27,7 +27,8 @@ static void devmap_managed_enable_put(void)
static int devmap_managed_enable_get(struct dev_pagemap *pgmap) { - if (!pgmap->ops || !pgmap->ops->page_free) { + if (pgmap->type == MEMORY_DEVICE_PRIVATE && + (!pgmap->ops || !pgmap->ops->page_free)) { WARN(1, "Missing page_free method\n"); return -EINVAL; } @@ -414,44 +415,51 @@ void __put_devmap_managed_page(struct page *page) { int count = page_ref_dec_return(page);
- /* - * If refcount is 1 then page is freed and refcount is stable as nobody - * holds a reference on the page. - */ - if (count == 1) { - /* Clear Active bit in case of parallel mark_page_accessed */ - __ClearPageActive(page); - __ClearPageWaiters(page); + /* still busy */ + if (count > 1) + return;
- mem_cgroup_uncharge(page); + /* only triggered by the dev_pagemap shutdown path */ + if (count == 0) { + __put_page(page); + return; + }
- /* - * When a device_private page is freed, the page->mapping field - * may still contain a (stale) mapping value. For example, the - * lower bits of page->mapping may still identify the page as - * an anonymous page. Ultimately, this entire field is just - * stale and wrong, and it will cause errors if not cleared. - * One example is: - * - * migrate_vma_pages() - * migrate_vma_insert_page() - * page_add_new_anon_rmap() - * __page_set_anon_rmap() - * ...checks page->mapping, via PageAnon(page) call, - * and incorrectly concludes that the page is an - * anonymous page. Therefore, it incorrectly, - * silently fails to set up the new anon rmap. - * - * For other types of ZONE_DEVICE pages, migration is either - * handled differently or not done at all, so there is no need - * to clear page->mapping. - */ - if (is_device_private_page(page)) - page->mapping = NULL; + /* notify page idle for dax */ + if (!is_device_private_page(page)) { + wake_up_var(&page->_refcount); + return; + }
- page->pgmap->ops->page_free(page); - } else if (!count) - __put_page(page); + /* Clear Active bit in case of parallel mark_page_accessed */ + __ClearPageActive(page); + __ClearPageWaiters(page); + + mem_cgroup_uncharge(page); + + /* + * When a device_private page is freed, the page->mapping field + * may still contain a (stale) mapping value. For example, the + * lower bits of page->mapping may still identify the page as an + * anonymous page. Ultimately, this entire field is just stale + * and wrong, and it will cause errors if not cleared. One + * example is: + * + * migrate_vma_pages() + * migrate_vma_insert_page() + * page_add_new_anon_rmap() + * __page_set_anon_rmap() + * ...checks page->mapping, via PageAnon(page) call, + * and incorrectly concludes that the page is an + * anonymous page. Therefore, it incorrectly, + * silently fails to set up the new anon rmap. + * + * For other types of ZONE_DEVICE pages, migration is either + * handled differently or not done at all, so there is no need + * to clear page->mapping. + */ + page->mapping = NULL; + page->pgmap->ops->page_free(page); } EXPORT_SYMBOL(__put_devmap_managed_page); #endif /* CONFIG_DEV_PAGEMAP_OPS */
An upcoming patch changes and complicates the refcounting and especially the "put page" aspects of it. In order to keep everything clean, refactor the devmap page release routines:
* Rename put_devmap_managed_page() to page_is_devmap_managed(), and limit the functionality to "read only": return a bool, with no side effects.
* Add a new routine, put_devmap_managed_page(), to handle decrementing the refcount for ZONE_DEVICE pages.
* Change callers (just release_pages() and put_page()) to check page_is_devmap_managed() before calling the new put_devmap_managed_page() routine. This is a performance point: put_page() is a hot path, so we need to avoid non- inline function calls where possible.
* Rename __put_devmap_managed_page() to free_devmap_managed_page(), and limit the functionality to unconditionally freeing a devmap page.
This is originally based on a separate patch by Ira Weiny, which applied to an early version of the put_user_page() experiments. Since then, Jérôme Glisse suggested the refactoring described above.
Cc: Christoph Hellwig hch@lst.de Cc: Kirill A. Shutemov kirill@shutemov.name Suggested-by: Jérôme Glisse jglisse@redhat.com Reviewed-by: Dan Williams dan.j.williams@intel.com Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- include/linux/mm.h | 18 +++++++++++++----- mm/memremap.c | 15 +-------------- mm/swap.c | 27 ++++++++++++++++++++++++++- 3 files changed, 40 insertions(+), 20 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h index 80a9162b406c..e2032ff640eb 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -952,9 +952,10 @@ static inline bool is_zone_device_page(const struct page *page) #endif
#ifdef CONFIG_DEV_PAGEMAP_OPS -void __put_devmap_managed_page(struct page *page); +void free_devmap_managed_page(struct page *page); DECLARE_STATIC_KEY_FALSE(devmap_managed_key); -static inline bool put_devmap_managed_page(struct page *page) + +static inline bool page_is_devmap_managed(struct page *page) { if (!static_branch_unlikely(&devmap_managed_key)) return false; @@ -963,7 +964,6 @@ static inline bool put_devmap_managed_page(struct page *page) switch (page->pgmap->type) { case MEMORY_DEVICE_PRIVATE: case MEMORY_DEVICE_FS_DAX: - __put_devmap_managed_page(page); return true; default: break; @@ -971,11 +971,17 @@ static inline bool put_devmap_managed_page(struct page *page) return false; }
+void put_devmap_managed_page(struct page *page); + #else /* CONFIG_DEV_PAGEMAP_OPS */ -static inline bool put_devmap_managed_page(struct page *page) +static inline bool page_is_devmap_managed(struct page *page) { return false; } + +static inline void put_devmap_managed_page(struct page *page) +{ +} #endif /* CONFIG_DEV_PAGEMAP_OPS */
static inline bool is_device_private_page(const struct page *page) @@ -1028,8 +1034,10 @@ static inline void put_page(struct page *page) * need to inform the device driver through callback. See * include/linux/memremap.h and HMM for details. */ - if (put_devmap_managed_page(page)) + if (page_is_devmap_managed(page)) { + put_devmap_managed_page(page); return; + }
if (put_page_testzero(page)) __put_page(page); diff --git a/mm/memremap.c b/mm/memremap.c index f915d074ac20..4c723d2049d5 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -411,20 +411,8 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, EXPORT_SYMBOL_GPL(get_dev_pagemap);
#ifdef CONFIG_DEV_PAGEMAP_OPS -void __put_devmap_managed_page(struct page *page) +void free_devmap_managed_page(struct page *page) { - int count = page_ref_dec_return(page); - - /* still busy */ - if (count > 1) - return; - - /* only triggered by the dev_pagemap shutdown path */ - if (count == 0) { - __put_page(page); - return; - } - /* notify page idle for dax */ if (!is_device_private_page(page)) { wake_up_var(&page->_refcount); @@ -461,5 +449,4 @@ void __put_devmap_managed_page(struct page *page) page->mapping = NULL; page->pgmap->ops->page_free(page); } -EXPORT_SYMBOL(__put_devmap_managed_page); #endif /* CONFIG_DEV_PAGEMAP_OPS */ diff --git a/mm/swap.c b/mm/swap.c index 5341ae93861f..cf39d24ada2a 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -813,8 +813,10 @@ void release_pages(struct page **pages, int nr) * processing, and instead, expect a call to * put_page_testzero(). */ - if (put_devmap_managed_page(page)) + if (page_is_devmap_managed(page)) { + put_devmap_managed_page(page); continue; + } }
page = compound_head(page); @@ -1102,3 +1104,26 @@ void __init swap_setup(void) * _really_ don't want to cluster much more */ } + +#ifdef CONFIG_DEV_PAGEMAP_OPS +void put_devmap_managed_page(struct page *page) +{ + int count; + + if (WARN_ON_ONCE(!page_is_devmap_managed(page))) + return; + + count = page_ref_dec_return(page); + + /* + * devmap page refcounts are 1-based, rather than 0-based: if + * refcount is 1, then the page is free and the refcount is + * stable because nobody holds a reference on the page. + */ + if (count == 1) + free_devmap_managed_page(page); + else if (!count) + __put_page(page); +} +EXPORT_SYMBOL(put_devmap_managed_page); +#endif
On Tue, Jan 07, 2020 at 02:45:40PM -0800, John Hubbard wrote:
An upcoming patch changes and complicates the refcounting and especially the "put page" aspects of it. In order to keep everything clean, refactor the devmap page release routines:
Rename put_devmap_managed_page() to page_is_devmap_managed(), and limit the functionality to "read only": return a bool, with no side effects.
Add a new routine, put_devmap_managed_page(), to handle decrementing the refcount for ZONE_DEVICE pages.
Change callers (just release_pages() and put_page()) to check page_is_devmap_managed() before calling the new put_devmap_managed_page() routine. This is a performance point: put_page() is a hot path, so we need to avoid non- inline function calls where possible.
Rename __put_devmap_managed_page() to free_devmap_managed_page(), and limit the functionality to unconditionally freeing a devmap page.
This is originally based on a separate patch by Ira Weiny, which applied to an early version of the put_user_page() experiments. Since then, Jérôme Glisse suggested the refactoring described above.
I'm really not sold on this scheme. Note that I think it is particularly bad, but it also doesn't seem any better than what we had before, and it introduced quite a bit more code.
On 1/15/20 7:23 AM, Christoph Hellwig wrote: ...
I'm really not sold on this scheme. Note that I think it is particularly bad, but it also doesn't seem any better than what we had before, and it introduced quite a bit more code.
Hi Christoph,
All by itself, yes. But the very next patch (which needs a little rework for other reasons, so not included here) needs to reuse some of these functions within __unpin_devmap_managed_user_page():
page_is_devmap_managed() free_devmap_managed_page()
That patch was posted as part of the v11 series [1], and it did this:
+#ifdef CONFIG_DEV_PAGEMAP_OPS +static bool __unpin_devmap_managed_user_page(struct page *page) +{ + int count; + + if (!page_is_devmap_managed(page)) + return false; + + count = page_ref_sub_return(page, GUP_PIN_COUNTING_BIAS); + + __update_proc_vmstat(page, NR_FOLL_PIN_RETURNED, 1); + /* + * devmap page refcounts are 1-based, rather than 0-based: if + * refcount is 1, then the page is free and the refcount is + * stable because nobody holds a reference on the page. + */ + if (count == 1) + free_devmap_managed_page(page); + else if (!count) + __put_page(page); + + return true; +} +#else +static bool __unpin_devmap_managed_user_page(struct page *page) +{ + return false; +} +#endif /* CONFIG_DEV_PAGEMAP_OPS */ + +/** + * unpin_user_page() - release a dma-pinned page + * @page: pointer to page to be released + * + * Pages that were pinned via pin_user_pages*() must be released via either + * unpin_user_page(), or one of the unpin_user_pages*() routines. This is so + * that such pages can be separately tracked and uniquely handled. In + * particular, interactions with RDMA and filesystems need special handling. + */ +void unpin_user_page(struct page *page) +{ + page = compound_head(page); + + /* + * For devmap managed pages we need to catch refcount transition from + * GUP_PIN_COUNTING_BIAS to 1, when refcount reach one it means the + * page is free and we need to inform the device driver through + * callback. See include/linux/memremap.h and HMM for details. + */ + if (__unpin_devmap_managed_user_page(page)) + return; + + if (page_ref_sub_and_test(page, GUP_PIN_COUNTING_BIAS)) + __put_page(page); + + __update_proc_vmstat(page, NR_FOLL_PIN_RETURNED, 1); +} +EXPORT_SYMBOL(unpin_user_page);
[1] https://lore.kernel.org/r/20191216222537.491123-24-jhubbard@nvidia.com [PATCH v11 23/25] mm/gup: track FOLL_PIN pages
thanks,
On Wed, Jan 15, 2020 at 01:19:41PM -0800, John Hubbard wrote:
On 1/15/20 7:23 AM, Christoph Hellwig wrote: ...
I'm really not sold on this scheme. Note that I think it is particularly bad, but it also doesn't seem any better than what we had before, and it introduced quite a bit more code.
Hi Christoph,
All by itself, yes. But the very next patch (which needs a little rework for other reasons, so not included here) needs to reuse some of these functions within __unpin_devmap_managed_user_page():
Well, then combine it with the series that actually does the change.
Also my vaguely recollection is that we had some idea on how to get rid of the off by one refcounting for the zone device pages, which would be a much better outcome.
On 1/16/20 1:37 AM, Christoph Hellwig wrote:
On Wed, Jan 15, 2020 at 01:19:41PM -0800, John Hubbard wrote:
On 1/15/20 7:23 AM, Christoph Hellwig wrote: ...
I'm really not sold on this scheme. Note that I think it is particularly bad, but it also doesn't seem any better than what we had before, and it introduced quite a bit more code.
Hi Christoph,
All by itself, yes. But the very next patch (which needs a little rework for other reasons, so not included here) needs to reuse some of these functions within __unpin_devmap_managed_user_page():
Well, then combine it with the series that actually does the change.
OK, that makes sense. I just double-checked with a quick test run, that it doesn't have dependencies with the rest of this series, and it came out clean, so:
Andrew, could you please remove just this one patch from mmotm and linux-next?
Also my vaguely recollection is that we had some idea on how to get rid of the off by one refcounting for the zone device pages, which would be a much better outcome.
Yes, I recall that Dan Williams mentioned it, but I don't think he provided any details yet.
thanks,
1. Avoid naming conflicts: rename local static function from "pin_user_pages()" to "goldfish_pin_pages()".
An upcoming patch will introduce a global pin_user_pages() function.
Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Jérôme Glisse jglisse@redhat.com Reviewed-by: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/platform/goldfish/goldfish_pipe.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c index cef0133aa47a..ef50c264db71 100644 --- a/drivers/platform/goldfish/goldfish_pipe.c +++ b/drivers/platform/goldfish/goldfish_pipe.c @@ -257,12 +257,12 @@ static int goldfish_pipe_error_convert(int status) } }
-static int pin_user_pages(unsigned long first_page, - unsigned long last_page, - unsigned int last_page_size, - int is_write, - struct page *pages[MAX_BUFFERS_PER_COMMAND], - unsigned int *iter_last_page_size) +static int goldfish_pin_pages(unsigned long first_page, + unsigned long last_page, + unsigned int last_page_size, + int is_write, + struct page *pages[MAX_BUFFERS_PER_COMMAND], + unsigned int *iter_last_page_size) { int ret; int requested_pages = ((last_page - first_page) >> PAGE_SHIFT) + 1; @@ -354,9 +354,9 @@ static int transfer_max_buffers(struct goldfish_pipe *pipe, if (mutex_lock_interruptible(&pipe->lock)) return -ERESTARTSYS;
- pages_count = pin_user_pages(first_page, last_page, - last_page_size, is_write, - pipe->pages, &iter_last_page_size); + pages_count = goldfish_pin_pages(first_page, last_page, + last_page_size, is_write, + pipe->pages, &iter_last_page_size); if (pages_count < 0) { mutex_unlock(&pipe->lock); return pages_count;
Looks good,
Reviewed-by: Christoph Hellwig hch@lst.de
As it says in the updated comment in gup.c: current FOLL_LONGTERM behavior is incompatible with FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on vmas.
However, the corresponding restriction in get_user_pages_remote() was slightly stricter than is actually required: it forbade all FOLL_LONGTERM callers, but we can actually allow FOLL_LONGTERM callers that do not set the "locked" arg.
Update the code and comments to loosen the restriction, allowing FOLL_LONGTERM in some cases.
Also, copy the DAX check ("if a VMA is DAX, don't allow long term pinning") from the VFIO call site, all the way into the internals of get_user_pages_remote() and __gup_longterm_locked(). That is: get_user_pages_remote() calls __gup_longterm_locked(), which in turn calls check_dax_vmas(). This check will then be removed from the VFIO call site in a subsequent patch.
Thanks to Jason Gunthorpe for pointing out a clean way to fix this, and to Dan Williams for helping clarify the DAX refactoring.
Tested-by: Alex Williamson alex.williamson@redhat.com Acked-by: Alex Williamson alex.williamson@redhat.com Reviewed-by: Jason Gunthorpe jgg@mellanox.com Reviewed-by: Ira Weiny ira.weiny@intel.com Suggested-by: Jason Gunthorpe jgg@ziepe.ca Cc: Kirill A. Shutemov kirill@shutemov.name Cc: Dan Williams dan.j.williams@intel.com Cc: Jerome Glisse jglisse@redhat.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- mm/gup.c | 174 +++++++++++++++++++++++++++++-------------------------- 1 file changed, 92 insertions(+), 82 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index 5938e29a5a8b..b61bd5c469ae 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1111,88 +1111,6 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk, return pages_done; }
-/* - * get_user_pages_remote() - pin user pages in memory - * @tsk: the task_struct to use for page fault accounting, or - * NULL if faults are not to be recorded. - * @mm: mm_struct of target mm - * @start: starting user address - * @nr_pages: number of pages from start to pin - * @gup_flags: flags modifying lookup behaviour - * @pages: array that receives pointers to the pages pinned. - * Should be at least nr_pages long. Or NULL, if caller - * only intends to ensure the pages are faulted in. - * @vmas: array of pointers to vmas corresponding to each page. - * Or NULL if the caller does not require them. - * @locked: pointer to lock flag indicating whether lock is held and - * subsequently whether VM_FAULT_RETRY functionality can be - * utilised. Lock must initially be held. - * - * Returns either number of pages pinned (which may be less than the - * number requested), or an error. Details about the return value: - * - * -- If nr_pages is 0, returns 0. - * -- If nr_pages is >0, but no pages were pinned, returns -errno. - * -- If nr_pages is >0, and some pages were pinned, returns the number of - * pages pinned. Again, this may be less than nr_pages. - * - * The caller is responsible for releasing returned @pages, via put_page(). - * - * @vmas are valid only as long as mmap_sem is held. - * - * Must be called with mmap_sem held for read or write. - * - * get_user_pages walks a process's page tables and takes a reference to - * each struct page that each user address corresponds to at a given - * instant. That is, it takes the page that would be accessed if a user - * thread accesses the given user virtual address at that instant. - * - * This does not guarantee that the page exists in the user mappings when - * get_user_pages returns, and there may even be a completely different - * page there in some cases (eg. if mmapped pagecache has been invalidated - * and subsequently re faulted). However it does guarantee that the page - * won't be freed completely. And mostly callers simply care that the page - * contains data that was valid *at some point in time*. Typically, an IO - * or similar operation cannot guarantee anything stronger anyway because - * locks can't be held over the syscall boundary. - * - * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page - * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must - * be called after the page is finished with, and before put_page is called. - * - * get_user_pages is typically used for fewer-copy IO operations, to get a - * handle on the memory by some means other than accesses via the user virtual - * addresses. The pages may be submitted for DMA to devices or accessed via - * their kernel linear mapping (via the kmap APIs). Care should be taken to - * use the correct cache flushing APIs. - * - * See also get_user_pages_fast, for performance critical applications. - * - * get_user_pages should be phased out in favor of - * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing - * should use get_user_pages because it cannot pass - * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. - */ -long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, - unsigned long start, unsigned long nr_pages, - unsigned int gup_flags, struct page **pages, - struct vm_area_struct **vmas, int *locked) -{ - /* - * FIXME: Current FOLL_LONGTERM behavior is incompatible with - * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on - * vmas. As there are no users of this flag in this call we simply - * disallow this option for now. - */ - if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) - return -EINVAL; - - return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas, - locked, - gup_flags | FOLL_TOUCH | FOLL_REMOTE); -} -EXPORT_SYMBOL(get_user_pages_remote); - /** * populate_vma_page_range() - populate a range of pages in the vma. * @vma: target vma @@ -1626,6 +1544,98 @@ static __always_inline long __gup_longterm_locked(struct task_struct *tsk, } #endif /* CONFIG_FS_DAX || CONFIG_CMA */
+/* + * get_user_pages_remote() - pin user pages in memory + * @tsk: the task_struct to use for page fault accounting, or + * NULL if faults are not to be recorded. + * @mm: mm_struct of target mm + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying lookup behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * @vmas: array of pointers to vmas corresponding to each page. + * Or NULL if the caller does not require them. + * @locked: pointer to lock flag indicating whether lock is held and + * subsequently whether VM_FAULT_RETRY functionality can be + * utilised. Lock must initially be held. + * + * Returns either number of pages pinned (which may be less than the + * number requested), or an error. Details about the return value: + * + * -- If nr_pages is 0, returns 0. + * -- If nr_pages is >0, but no pages were pinned, returns -errno. + * -- If nr_pages is >0, and some pages were pinned, returns the number of + * pages pinned. Again, this may be less than nr_pages. + * + * The caller is responsible for releasing returned @pages, via put_page(). + * + * @vmas are valid only as long as mmap_sem is held. + * + * Must be called with mmap_sem held for read or write. + * + * get_user_pages walks a process's page tables and takes a reference to + * each struct page that each user address corresponds to at a given + * instant. That is, it takes the page that would be accessed if a user + * thread accesses the given user virtual address at that instant. + * + * This does not guarantee that the page exists in the user mappings when + * get_user_pages returns, and there may even be a completely different + * page there in some cases (eg. if mmapped pagecache has been invalidated + * and subsequently re faulted). However it does guarantee that the page + * won't be freed completely. And mostly callers simply care that the page + * contains data that was valid *at some point in time*. Typically, an IO + * or similar operation cannot guarantee anything stronger anyway because + * locks can't be held over the syscall boundary. + * + * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page + * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must + * be called after the page is finished with, and before put_page is called. + * + * get_user_pages is typically used for fewer-copy IO operations, to get a + * handle on the memory by some means other than accesses via the user virtual + * addresses. The pages may be submitted for DMA to devices or accessed via + * their kernel linear mapping (via the kmap APIs). Care should be taken to + * use the correct cache flushing APIs. + * + * See also get_user_pages_fast, for performance critical applications. + * + * get_user_pages should be phased out in favor of + * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing + * should use get_user_pages because it cannot pass + * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. + */ +long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, int *locked) +{ + /* + * Parts of FOLL_LONGTERM behavior are incompatible with + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on + * vmas. However, this only comes up if locked is set, and there are + * callers that do request FOLL_LONGTERM, but do not set locked. So, + * allow what we can. + */ + if (gup_flags & FOLL_LONGTERM) { + if (WARN_ON_ONCE(locked)) + return -EINVAL; + /* + * This will check the vmas (even if our vmas arg is NULL) + * and return -ENOTSUPP if DAX isn't allowed in this case: + */ + return __gup_longterm_locked(tsk, mm, start, nr_pages, pages, + vmas, gup_flags | FOLL_TOUCH | + FOLL_REMOTE); + } + + return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas, + locked, + gup_flags | FOLL_TOUCH | FOLL_REMOTE); +} +EXPORT_SYMBOL(get_user_pages_remote); + /* * This is the same as get_user_pages_remote(), just with a * less-flexible calling convention where we assume that the task
Looks good,
Reviewed-by: Christoph Hellwig hch@lst.de
Update VFIO to take advantage of the recently loosened restriction on FOLL_LONGTERM with get_user_pages_remote(). Also, now it is possible to fix a bug: the VFIO caller is logically a FOLL_LONGTERM user, but it wasn't setting FOLL_LONGTERM.
Also, remove an unnessary pair of calls that were releasing and reacquiring the mmap_sem. There is no need to avoid holding mmap_sem just in order to call page_to_pfn().
Also, now that the the DAX check ("if a VMA is DAX, don't allow long term pinning") is in the internals of get_user_pages_remote() and __gup_longterm_locked(), there's no need for it at the VFIO call site. So remove it.
Tested-by: Alex Williamson alex.williamson@redhat.com Acked-by: Alex Williamson alex.williamson@redhat.com Reviewed-by: Jason Gunthorpe jgg@mellanox.com Reviewed-by: Ira Weiny ira.weiny@intel.com Suggested-by: Jason Gunthorpe jgg@ziepe.ca Cc: Dan Williams dan.j.williams@intel.com Cc: Jerome Glisse jglisse@redhat.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/vfio/vfio_iommu_type1.c | 30 +++++------------------------- 1 file changed, 5 insertions(+), 25 deletions(-)
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 2ada8e6cdb88..b800fc9a0251 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -322,7 +322,6 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, { struct page *page[1]; struct vm_area_struct *vma; - struct vm_area_struct *vmas[1]; unsigned int flags = 0; int ret;
@@ -330,33 +329,14 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, flags |= FOLL_WRITE;
down_read(&mm->mmap_sem); - if (mm == current->mm) { - ret = get_user_pages(vaddr, 1, flags | FOLL_LONGTERM, page, - vmas); - } else { - ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page, - vmas, NULL); - /* - * The lifetime of a vaddr_get_pfn() page pin is - * userspace-controlled. In the fs-dax case this could - * lead to indefinite stalls in filesystem operations. - * Disallow attempts to pin fs-dax pages via this - * interface. - */ - if (ret > 0 && vma_is_fsdax(vmas[0])) { - ret = -EOPNOTSUPP; - put_page(page[0]); - } - } - up_read(&mm->mmap_sem); - + ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags | FOLL_LONGTERM, + page, NULL, NULL); if (ret == 1) { *pfn = page_to_pfn(page[0]); - return 0; + ret = 0; + goto done; }
- down_read(&mm->mmap_sem); - vaddr = untagged_addr(vaddr);
vma = find_vma_intersection(mm, vaddr, vaddr + 1); @@ -366,7 +346,7 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, if (is_invalid_reserved_pfn(*pfn)) ret = 0; } - +done: up_read(&mm->mmap_sem); return ret; }
Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast(). This, combined with the fact that get_user_pages_fast() falls back to "slow gup", which *does* accept FOLL_FORCE, leads to an odd situation: if you need FOLL_FORCE, you cannot call get_user_pages_fast().
There does not appear to be any reason for filtering out FOLL_FORCE. There is nothing in the _fast() implementation that requires that we avoid writing to the pages. So it appears to have been an oversight.
Fix by allowing FOLL_FORCE to be set for get_user_pages_fast().
Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags") Cc: Christoph Hellwig hch@lst.de Reviewed-by: Leon Romanovsky leonro@mellanox.com Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: John Hubbard jhubbard@nvidia.com --- mm/gup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/gup.c b/mm/gup.c index b61bd5c469ae..a594bc708367 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2411,7 +2411,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages, unsigned long addr, len, end; int nr = 0, ret = 0;
- if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM))) + if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | + FOLL_FORCE))) return -EINVAL;
start = untagged_addr(start) & PAGE_MASK;
Looks good,
Reviewed-by: Christoph Hellwig hch@lst.de
And get rid of the mmap_sem calls, as part of that. Note that get_user_pages_fast() will, if necessary, fall back to __gup_longterm_unlocked(), which takes the mmap_sem as needed.
Reviewed-by: Leon Romanovsky leonro@mellanox.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Jason Gunthorpe jgg@mellanox.com Reviewed-by: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/infiniband/core/umem.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c index 7a3b99597ead..214e87aa609d 100644 --- a/drivers/infiniband/core/umem.c +++ b/drivers/infiniband/core/umem.c @@ -266,16 +266,13 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr, sg = umem->sg_head.sgl;
while (npages) { - down_read(&mm->mmap_sem); - ret = get_user_pages(cur_base, - min_t(unsigned long, npages, - PAGE_SIZE / sizeof (struct page *)), - gup_flags | FOLL_LONGTERM, - page_list, NULL); - if (ret < 0) { - up_read(&mm->mmap_sem); + ret = get_user_pages_fast(cur_base, + min_t(unsigned long, npages, + PAGE_SIZE / + sizeof(struct page *)), + gup_flags | FOLL_LONGTERM, page_list); + if (ret < 0) goto umem_release; - }
cur_base += ret * PAGE_SIZE; npages -= ret; @@ -283,8 +280,6 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr, sg = ib_umem_add_sg_table(sg, page_list, ret, dma_get_max_seg_size(context->device->dma_device), &umem->sg_nents); - - up_read(&mm->mmap_sem); }
sg_mark_end(sg);
After DMA is complete, and the device and CPU caches are synchronized, it's still required to mark the CPU pages as dirty, if the data was coming from the device. However, this driver was just issuing a bare put_page() call, without any set_page_dirty*() call.
Fix the problem, by calling set_page_dirty_lock() if the CPU pages were potentially receiving data from the device.
Reviewed-by: Christoph Hellwig hch@lst.de Acked-by: Hans Verkuil hverkuil-cisco@xs4all.nl Cc: Mauro Carvalho Chehab mchehab@kernel.org Cc: stable@vger.kernel.org Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/media/v4l2-core/videobuf-dma-sg.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c index 66a6c6c236a7..28262190c3ab 100644 --- a/drivers/media/v4l2-core/videobuf-dma-sg.c +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c @@ -349,8 +349,11 @@ int videobuf_dma_free(struct videobuf_dmabuf *dma) BUG_ON(dma->sglen);
if (dma->pages) { - for (i = 0; i < dma->nr_pages; i++) + for (i = 0; i < dma->nr_pages; i++) { + if (dma->direction == DMA_FROM_DEVICE) + set_page_dirty_lock(dma->pages[i]); put_page(dma->pages[i]); + } kfree(dma->pages); dma->pages = NULL; }
Introduce pin_user_pages*() variations of get_user_pages*() calls, and also pin_longterm_pages*() variations.
For now, these are placeholder calls, until the various call sites are converted to use the correct get_user_pages*() or pin_user_pages*() API.
These variants will eventually all set FOLL_PIN, which is also introduced, and thoroughly documented.
pin_user_pages() pin_user_pages_remote() pin_user_pages_fast()
All pages that are pinned via the above calls, must be unpinned via put_user_page().
The underlying rules are:
* FOLL_PIN is a gup-internal flag, so the call sites should not directly set it. That behavior is enforced with assertions.
* Call sites that want to indicate that they are going to do DirectIO ("DIO") or something with similar characteristics, should call a get_user_pages()-like wrapper call that sets FOLL_PIN. These wrappers will: * Start with "pin_user_pages" instead of "get_user_pages". That makes it easy to find and audit the call sites. * Set FOLL_PIN
* For pages that are received via FOLL_PIN, those pages must be returned via put_user_page().
Thanks to Jan Kara and Vlastimil Babka for explaining the 4 cases in this documentation. (I've reworded it and expanded upon it.)
Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Mike Rapoport rppt@linux.ibm.com # Documentation Reviewed-by: Jérôme Glisse jglisse@redhat.com Cc: Jonathan Corbet corbet@lwn.net Cc: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- Documentation/core-api/index.rst | 1 + Documentation/core-api/pin_user_pages.rst | 232 ++++++++++++++++++++++ include/linux/mm.h | 63 ++++-- mm/gup.c | 164 +++++++++++++-- 4 files changed, 426 insertions(+), 34 deletions(-) create mode 100644 Documentation/core-api/pin_user_pages.rst
diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index ab0eae1c153a..413f7d7c8642 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -31,6 +31,7 @@ Core utilities generic-radix-tree memory-allocation mm-api + pin_user_pages gfp_mask-from-fs-io timekeeping boot-time-mm diff --git a/Documentation/core-api/pin_user_pages.rst b/Documentation/core-api/pin_user_pages.rst new file mode 100644 index 000000000000..71849830cd48 --- /dev/null +++ b/Documentation/core-api/pin_user_pages.rst @@ -0,0 +1,232 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================================================== +pin_user_pages() and related calls +==================================================== + +.. contents:: :local: + +Overview +======== + +This document describes the following functions:: + + pin_user_pages() + pin_user_pages_fast() + pin_user_pages_remote() + +Basic description of FOLL_PIN +============================= + +FOLL_PIN and FOLL_LONGTERM are flags that can be passed to the get_user_pages*() +("gup") family of functions. FOLL_PIN has significant interactions and +interdependencies with FOLL_LONGTERM, so both are covered here. + +FOLL_PIN is internal to gup, meaning that it should not appear at the gup call +sites. This allows the associated wrapper functions (pin_user_pages*() and +others) to set the correct combination of these flags, and to check for problems +as well. + +FOLL_LONGTERM, on the other hand, *is* allowed to be set at the gup call sites. +This is in order to avoid creating a large number of wrapper functions to cover +all combinations of get*(), pin*(), FOLL_LONGTERM, and more. Also, the +pin_user_pages*() APIs are clearly distinct from the get_user_pages*() APIs, so +that's a natural dividing line, and a good point to make separate wrapper calls. +In other words, use pin_user_pages*() for DMA-pinned pages, and +get_user_pages*() for other cases. There are four cases described later on in +this document, to further clarify that concept. + +FOLL_PIN and FOLL_GET are mutually exclusive for a given gup call. However, +multiple threads and call sites are free to pin the same struct pages, via both +FOLL_PIN and FOLL_GET. It's just the call site that needs to choose one or the +other, not the struct page(s). + +The FOLL_PIN implementation is nearly the same as FOLL_GET, except that FOLL_PIN +uses a different reference counting technique. + +FOLL_PIN is a prerequisite to FOLL_LONGTERM. Another way of saying that is, +FOLL_LONGTERM is a specific case, more restrictive case of FOLL_PIN. + +Which flags are set by each wrapper +=================================== + +For these pin_user_pages*() functions, FOLL_PIN is OR'd in with whatever gup +flags the caller provides. The caller is required to pass in a non-null struct +pages* array, and the function then pin pages by incrementing each by a special +value. For now, that value is +1, just like get_user_pages*().:: + + Function + -------- + pin_user_pages FOLL_PIN is always set internally by this function. + pin_user_pages_fast FOLL_PIN is always set internally by this function. + pin_user_pages_remote FOLL_PIN is always set internally by this function. + +For these get_user_pages*() functions, FOLL_GET might not even be specified. +Behavior is a little more complex than above. If FOLL_GET was *not* specified, +but the caller passed in a non-null struct pages* array, then the function +sets FOLL_GET for you, and proceeds to pin pages by incrementing the refcount +of each page by +1.:: + + Function + -------- + get_user_pages FOLL_GET is sometimes set internally by this function. + get_user_pages_fast FOLL_GET is sometimes set internally by this function. + get_user_pages_remote FOLL_GET is sometimes set internally by this function. + +Tracking dma-pinned pages +========================= + +Some of the key design constraints, and solutions, for tracking dma-pinned +pages: + +* An actual reference count, per struct page, is required. This is because + multiple processes may pin and unpin a page. + +* False positives (reporting that a page is dma-pinned, when in fact it is not) + are acceptable, but false negatives are not. + +* struct page may not be increased in size for this, and all fields are already + used. + +* Given the above, we can overload the page->_refcount field by using, sort of, + the upper bits in that field for a dma-pinned count. "Sort of", means that, + rather than dividing page->_refcount into bit fields, we simple add a medium- + large value (GUP_PIN_COUNTING_BIAS, initially chosen to be 1024: 10 bits) to + page->_refcount. This provides fuzzy behavior: if a page has get_page() called + on it 1024 times, then it will appear to have a single dma-pinned count. + And again, that's acceptable. + +This also leads to limitations: there are only 31-10==21 bits available for a +counter that increments 10 bits at a time. + +TODO: for 1GB and larger huge pages, this is cutting it close. That's because +when pin_user_pages() follows such pages, it increments the head page by "1" +(where "1" used to mean "+1" for get_user_pages(), but now means "+1024" for +pin_user_pages()) for each tail page. So if you have a 1GB huge page: + +* There are 256K (18 bits) worth of 4 KB tail pages. +* There are 21 bits available to count up via GUP_PIN_COUNTING_BIAS (that is, + 10 bits at a time) +* There are 21 - 18 == 3 bits available to count. Except that there aren't, + because you need to allow for a few normal get_page() calls on the head page, + as well. Fortunately, the approach of using addition, rather than "hard" + bitfields, within page->_refcount, allows for sharing these bits gracefully. + But we're still looking at about 8 references. + +This, however, is a missing feature more than anything else, because it's easily +solved by addressing an obvious inefficiency in the original get_user_pages() +approach of retrieving pages: stop treating all the pages as if they were +PAGE_SIZE. Retrieve huge pages as huge pages. The callers need to be aware of +this, so some work is required. Once that's in place, this limitation mostly +disappears from view, because there will be ample refcounting range available. + +* Callers must specifically request "dma-pinned tracking of pages". In other + words, just calling get_user_pages() will not suffice; a new set of functions, + pin_user_page() and related, must be used. + +FOLL_PIN, FOLL_GET, FOLL_LONGTERM: when to use which flags +========================================================== + +Thanks to Jan Kara, Vlastimil Babka and several other -mm people, for describing +these categories: + +CASE 1: Direct IO (DIO) +----------------------- +There are GUP references to pages that are serving +as DIO buffers. These buffers are needed for a relatively short time (so they +are not "long term"). No special synchronization with page_mkclean() or +munmap() is provided. Therefore, flags to set at the call site are: :: + + FOLL_PIN + +...but rather than setting FOLL_PIN directly, call sites should use one of +the pin_user_pages*() routines that set FOLL_PIN. + +CASE 2: RDMA +------------ +There are GUP references to pages that are serving as DMA +buffers. These buffers are needed for a long time ("long term"). No special +synchronization with page_mkclean() or munmap() is provided. Therefore, flags +to set at the call site are: :: + + FOLL_PIN | FOLL_LONGTERM + +NOTE: Some pages, such as DAX pages, cannot be pinned with longterm pins. That's +because DAX pages do not have a separate page cache, and so "pinning" implies +locking down file system blocks, which is not (yet) supported in that way. + +CASE 3: Hardware with page faulting support +------------------------------------------- +Here, a well-written driver doesn't normally need to pin pages at all. However, +if the driver does choose to do so, it can register MMU notifiers for the range, +and will be called back upon invalidation. Either way (avoiding page pinning, or +using MMU notifiers to unpin upon request), there is proper synchronization with +both filesystem and mm (page_mkclean(), munmap(), etc). + +Therefore, neither flag needs to be set. + +In this case, ideally, neither get_user_pages() nor pin_user_pages() should be +called. Instead, the software should be written so that it does not pin pages. +This allows mm and filesystems to operate more efficiently and reliably. + +CASE 4: Pinning for struct page manipulation only +------------------------------------------------- +Here, normal GUP calls are sufficient, so neither flag needs to be set. + +page_dma_pinned(): the whole point of pinning +============================================= + +The whole point of marking pages as "DMA-pinned" or "gup-pinned" is to be able +to query, "is this page DMA-pinned?" That allows code such as page_mkclean() +(and file system writeback code in general) to make informed decisions about +what to do when a page cannot be unmapped due to such pins. + +What to do in those cases is the subject of a years-long series of discussions +and debates (see the References at the end of this document). It's a TODO item +here: fill in the details once that's worked out. Meanwhile, it's safe to say +that having this available: :: + + static inline bool page_dma_pinned(struct page *page) + +...is a prerequisite to solving the long-running gup+DMA problem. + +Another way of thinking about FOLL_GET, FOLL_PIN, and FOLL_LONGTERM +=================================================================== + +Another way of thinking about these flags is as a progression of restrictions: +FOLL_GET is for struct page manipulation, without affecting the data that the +struct page refers to. FOLL_PIN is a *replacement* for FOLL_GET, and is for +short term pins on pages whose data *will* get accessed. As such, FOLL_PIN is +a "more severe" form of pinning. And finally, FOLL_LONGTERM is an even more +restrictive case that has FOLL_PIN as a prerequisite: this is for pages that +will be pinned longterm, and whose data will be accessed. + +Unit testing +============ +This file:: + + tools/testing/selftests/vm/gup_benchmark.c + +has the following new calls to exercise the new pin*() wrapper functions: + +* PIN_FAST_BENCHMARK (./gup_benchmark -a) +* PIN_BENCHMARK (./gup_benchmark -b) + +You can monitor how many total dma-pinned pages have been acquired and released +since the system was booted, via two new /proc/vmstat entries: :: + + /proc/vmstat/nr_foll_pin_requested + /proc/vmstat/nr_foll_pin_requested + +Those are both going to show zero, unless CONFIG_DEBUG_VM is set. This is +because there is a noticeable performance drop in put_user_page(), when they +are activated. + +References +========== + +* `Some slow progress on get_user_pages() (Apr 2, 2019) https://lwn.net/Articles/784574/`_ +* `DMA and get_user_pages() (LPC: Dec 12, 2018) https://lwn.net/Articles/774411/`_ +* `The trouble with get_user_pages() (Apr 30, 2018) https://lwn.net/Articles/753027/`_ + +John Hubbard, October, 2019 diff --git a/include/linux/mm.h b/include/linux/mm.h index e2032ff640eb..f9653e666bf4 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1047,16 +1047,14 @@ static inline void put_page(struct page *page) * put_user_page() - release a gup-pinned page * @page: pointer to page to be released * - * Pages that were pinned via get_user_pages*() must be released via - * either put_user_page(), or one of the put_user_pages*() routines - * below. This is so that eventually, pages that are pinned via - * get_user_pages*() can be separately tracked and uniquely handled. In - * particular, interactions with RDMA and filesystems need special - * handling. + * Pages that were pinned via pin_user_pages*() must be released via either + * put_user_page(), or one of the put_user_pages*() routines. This is so that + * eventually such pages can be separately tracked and uniquely handled. In + * particular, interactions with RDMA and filesystems need special handling. * * put_user_page() and put_page() are not interchangeable, despite this early * implementation that makes them look the same. put_user_page() calls must - * be perfectly matched up with get_user_page() calls. + * be perfectly matched up with pin*() calls. */ static inline void put_user_page(struct page *page) { @@ -1514,9 +1512,16 @@ long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, struct vm_area_struct **vmas, int *locked); +long pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, int *locked); long get_user_pages(unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, struct vm_area_struct **vmas); +long pin_user_pages(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas); long get_user_pages_locked(unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, int *locked); long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, @@ -1524,6 +1529,8 @@ long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
int get_user_pages_fast(unsigned long start, int nr_pages, unsigned int gup_flags, struct page **pages); +int pin_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages);
int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc); int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, @@ -2587,13 +2594,15 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, #define FOLL_ANON 0x8000 /* don't do file mappings */ #define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see below */ #define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */ +#define FOLL_PIN 0x40000 /* pages must be released via put_user_page() */
/* - * NOTE on FOLL_LONGTERM: + * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each + * other. Here is what they mean, and how to use them: * * FOLL_LONGTERM indicates that the page will be held for an indefinite time - * period _often_ under userspace control. This is contrasted with - * iov_iter_get_pages() where usages which are transient. + * period _often_ under userspace control. This is in contrast to + * iov_iter_get_pages(), whose usages are transient. * * FIXME: For pages which are part of a filesystem, mappings are subject to the * lifetime enforced by the filesystem and we need guarantees that longterm @@ -2608,11 +2617,39 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, * Currently only get_user_pages() and get_user_pages_fast() support this flag * and calls to get_user_pages_[un]locked are specifically not allowed. This * is due to an incompatibility with the FS DAX check and - * FAULT_FLAG_ALLOW_RETRY + * FAULT_FLAG_ALLOW_RETRY. * - * In the CMA case: longterm pins in a CMA region would unnecessarily fragment - * that region. And so CMA attempts to migrate the page before pinning when + * In the CMA case: long term pins in a CMA region would unnecessarily fragment + * that region. And so, CMA attempts to migrate the page before pinning, when * FOLL_LONGTERM is specified. + * + * FOLL_PIN indicates that a special kind of tracking (not just page->_refcount, + * but an additional pin counting system) will be invoked. This is intended for + * anything that gets a page reference and then touches page data (for example, + * Direct IO). This lets the filesystem know that some non-file-system entity is + * potentially changing the pages' data. In contrast to FOLL_GET (whose pages + * are released via put_page()), FOLL_PIN pages must be released, ultimately, by + * a call to put_user_page(). + * + * FOLL_PIN is similar to FOLL_GET: both of these pin pages. They use different + * and separate refcounting mechanisms, however, and that means that each has + * its own acquire and release mechanisms: + * + * FOLL_GET: get_user_pages*() to acquire, and put_page() to release. + * + * FOLL_PIN: pin_user_pages*() to acquire, and put_user_pages to release. + * + * FOLL_PIN and FOLL_GET are mutually exclusive for a given function call. + * (The underlying pages may experience both FOLL_GET-based and FOLL_PIN-based + * calls applied to them, and that's perfectly OK. This is a constraint on the + * callers, not on the pages.) + * + * FOLL_PIN should be set internally by the pin_user_pages*() APIs, never + * directly by the caller. That's in order to help avoid mismatches when + * releasing pages: get_user_pages*() pages must be released via put_page(), + * while pin_user_pages*() pages must be released via put_user_page(). + * + * Please see Documentation/vm/pin_user_pages.rst for more information. */
static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags) diff --git a/mm/gup.c b/mm/gup.c index a594bc708367..1c200eeabd77 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -194,6 +194,10 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, spinlock_t *ptl; pte_t *ptep, pte;
+ /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET))) + return ERR_PTR(-EINVAL); retry: if (unlikely(pmd_bad(*pmd))) return no_page_table(vma, flags); @@ -811,7 +815,7 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
start = untagged_addr(start);
- VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); + VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
/* * If FOLL_FORCE is set then do not force a full fault as the hinting @@ -1035,7 +1039,16 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk, BUG_ON(*locked != 1); }
- if (pages) + /* + * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior + * is to set FOLL_GET if the caller wants pages[] filled in (but has + * carelessly failed to specify FOLL_GET), so keep doing that, but only + * for FOLL_GET, not for the newer FOLL_PIN. + * + * FOLL_PIN always expects pages to be non-null, but no need to assert + * that here, as any failures will be obvious enough. + */ + if (pages && !(flags & FOLL_PIN)) flags |= FOLL_GET;
pages_done = 0; @@ -1606,11 +1619,19 @@ static __always_inline long __gup_longterm_locked(struct task_struct *tsk, * should use get_user_pages because it cannot pass * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. */ +#ifdef CONFIG_MMU long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, struct vm_area_struct **vmas, int *locked) { + /* + * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, + * never directly by the caller, so enforce that with an assertion: + */ + if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) + return -EINVAL; + /* * Parts of FOLL_LONGTERM behavior are incompatible with * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on @@ -1636,6 +1657,16 @@ long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, } EXPORT_SYMBOL(get_user_pages_remote);
+#else /* CONFIG_MMU */ +long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, int *locked) +{ + return 0; +} +#endif /* !CONFIG_MMU */ + /* * This is the same as get_user_pages_remote(), just with a * less-flexible calling convention where we assume that the task @@ -1647,6 +1678,13 @@ long get_user_pages(unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, struct vm_area_struct **vmas) { + /* + * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, + * never directly by the caller, so enforce that with an assertion: + */ + if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) + return -EINVAL; + return __gup_longterm_locked(current, current->mm, start, nr_pages, pages, vmas, gup_flags | FOLL_TOUCH); } @@ -2389,30 +2427,15 @@ static int __gup_longterm_unlocked(unsigned long start, int nr_pages, return ret; }
-/** - * get_user_pages_fast() - pin user pages in memory - * @start: starting user address - * @nr_pages: number of pages from start to pin - * @gup_flags: flags modifying pin behaviour - * @pages: array that receives pointers to the pages pinned. - * Should be at least nr_pages long. - * - * Attempt to pin user pages in memory without taking mm->mmap_sem. - * If not successful, it will fall back to taking the lock and - * calling get_user_pages(). - * - * Returns number of pages pinned. This may be fewer than the number - * requested. If nr_pages is 0 or negative, returns 0. If no pages - * were pinned, returns -errno. - */ -int get_user_pages_fast(unsigned long start, int nr_pages, - unsigned int gup_flags, struct page **pages) +static int internal_get_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, + struct page **pages) { unsigned long addr, len, end; int nr = 0, ret = 0;
if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | - FOLL_FORCE))) + FOLL_FORCE | FOLL_PIN))) return -EINVAL;
start = untagged_addr(start) & PAGE_MASK; @@ -2452,4 +2475,103 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
return ret; } + +/** + * get_user_pages_fast() - pin user pages in memory + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Attempt to pin user pages in memory without taking mm->mmap_sem. + * If not successful, it will fall back to taking the lock and + * calling get_user_pages(). + * + * Returns number of pages pinned. This may be fewer than the number requested. + * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns + * -errno. + */ +int get_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + /* + * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, + * never directly by the caller, so enforce that: + */ + if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) + return -EINVAL; + + return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); +} EXPORT_SYMBOL_GPL(get_user_pages_fast); + +/** + * pin_user_pages_fast() - pin user pages in memory without taking locks + * + * For now, this is a placeholder function, until various call sites are + * converted to use the correct get_user_pages*() or pin_user_pages*() API. So, + * this is identical to get_user_pages_fast(). + * + * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It + * is NOT intended for Case 2 (RDMA: long-term pins). + */ +int pin_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + /* + * This is a placeholder, until the pin functionality is activated. + * Until then, just behave like the corresponding get_user_pages*() + * routine. + */ + return get_user_pages_fast(start, nr_pages, gup_flags, pages); +} +EXPORT_SYMBOL_GPL(pin_user_pages_fast); + +/** + * pin_user_pages_remote() - pin pages of a remote process (task != current) + * + * For now, this is a placeholder function, until various call sites are + * converted to use the correct get_user_pages*() or pin_user_pages*() API. So, + * this is identical to get_user_pages_remote(). + * + * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It + * is NOT intended for Case 2 (RDMA: long-term pins). + */ +long pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, int *locked) +{ + /* + * This is a placeholder, until the pin functionality is activated. + * Until then, just behave like the corresponding get_user_pages*() + * routine. + */ + return get_user_pages_remote(tsk, mm, start, nr_pages, gup_flags, pages, + vmas, locked); +} +EXPORT_SYMBOL(pin_user_pages_remote); + +/** + * pin_user_pages() - pin user pages in memory for use by other devices + * + * For now, this is a placeholder function, until various call sites are + * converted to use the correct get_user_pages*() or pin_user_pages*() API. So, + * this is identical to get_user_pages(). + * + * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It + * is NOT intended for Case 2 (RDMA: long-term pins). + */ +long pin_user_pages(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas) +{ + /* + * This is a placeholder, until the pin functionality is activated. + * Until then, just behave like the corresponding get_user_pages*() + * routine. + */ + return get_user_pages(start, nr_pages, gup_flags, pages, vmas); +} +EXPORT_SYMBOL(pin_user_pages);
On Tue, Jan 07, 2020 at 02:45:47PM -0800, John Hubbard wrote:
Introduce pin_user_pages*() variations of get_user_pages*() calls, and also pin_longterm_pages*() variations.
For now, these are placeholder calls, until the various call sites are converted to use the correct get_user_pages*() or pin_user_pages*() API.
What do the pure placeholders buy us? The API itself looks ok, but until it actually is properly implemented it doesn't help at all, and we've had all kinds of bad experiences with these sorts of stub APIs.
On 1/15/20 7:30 AM, Christoph Hellwig wrote:
On Tue, Jan 07, 2020 at 02:45:47PM -0800, John Hubbard wrote:
Introduce pin_user_pages*() variations of get_user_pages*() calls, and also pin_longterm_pages*() variations.
For now, these are placeholder calls, until the various call sites are converted to use the correct get_user_pages*() or pin_user_pages*() API.
What do the pure placeholders buy us? The API itself looks ok, but until it actually is properly implemented it doesn't help at all, and we've had all kinds of bad experiences with these sorts of stub APIs.
Hi Christoph,
Absolutely agreed, and in fact, after spending some time in this area I am getting a much better understanding of just how problematic "this will be used soon" APIs really are. However, this is not quite that case.
The following things make this different from a "pure placeholder" API:
1) These APIs are all exercised in the following patches in this series, unless I've overlooked one, and
2) The pages are actually tracked in the very next patch that I want to post. That patch was posted as part of the v11 series [1], but Leon Romanovsky reported a problem with it, and so I'm going to add in the ability to handle larger "pin" refcounts for the huge page cases.
Meanwhile, I wanted to get these long-simmering simpler preparatory patches submitted, because it's clear that the API is unaffected by the huge page refcount fix. (That fix will likely use the second struct page of the compound page, to count up higher.)
[1] https://lore.kernel.org/r/20191216222537.491123-24-jhubbard@nvidia.com [PATCH v11 23/25] mm/gup: track FOLL_PIN pages
thanks,
1. Call the new global pin_user_pages_fast(), from pin_goldfish_pages().
2. As required by pin_user_pages(), release these pages via put_user_page(). In this case, do so via put_user_pages_dirty_lock().
That has the side effect of calling set_page_dirty_lock(), instead of set_page_dirty(). This is probably more accurate.
As Christoph Hellwig put it, "set_page_dirty() is only safe if we are dealing with a file backed page where we have reference on the inode it hangs off." [1]
Another side effect is that the release code is simplified because the page[] loop is now in gup.c instead of here, so just delete the local release_user_pages() entirely, and call put_user_pages_dirty_lock() directly, instead.
[1] https://lore.kernel.org/r/20190723153640.GB720@lst.de
Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/platform/goldfish/goldfish_pipe.c | 17 +++-------------- 1 file changed, 3 insertions(+), 14 deletions(-)
diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c index ef50c264db71..2a5901efecde 100644 --- a/drivers/platform/goldfish/goldfish_pipe.c +++ b/drivers/platform/goldfish/goldfish_pipe.c @@ -274,7 +274,7 @@ static int goldfish_pin_pages(unsigned long first_page, *iter_last_page_size = last_page_size; }
- ret = get_user_pages_fast(first_page, requested_pages, + ret = pin_user_pages_fast(first_page, requested_pages, !is_write ? FOLL_WRITE : 0, pages); if (ret <= 0) @@ -285,18 +285,6 @@ static int goldfish_pin_pages(unsigned long first_page, return ret; }
-static void release_user_pages(struct page **pages, int pages_count, - int is_write, s32 consumed_size) -{ - int i; - - for (i = 0; i < pages_count; i++) { - if (!is_write && consumed_size > 0) - set_page_dirty(pages[i]); - put_page(pages[i]); - } -} - /* Populate the call parameters, merging adjacent pages together */ static void populate_rw_params(struct page **pages, int pages_count, @@ -372,7 +360,8 @@ static int transfer_max_buffers(struct goldfish_pipe *pipe,
*consumed_size = pipe->command_buffer->rw_params.consumed_size;
- release_user_pages(pipe->pages, pages_count, is_write, *consumed_size); + put_user_pages_dirty_lock(pipe->pages, pages_count, + !is_write && *consumed_size > 0);
mutex_unlock(&pipe->lock); return 0;
Convert infiniband to use the new pin_user_pages*() calls.
Also, revert earlier changes to Infiniband ODP that had it using put_user_page(). ODP is "Case 3" in Documentation/core-api/pin_user_pages.rst, which is to say, normal get_user_pages() and put_page() is the API to use there.
The new pin_user_pages*() calls replace corresponding get_user_pages*() calls, and set the FOLL_PIN flag. The FOLL_PIN flag requires that the caller must return the pages via put_user_page*() calls, but infiniband was already doing that as part of an earlier commit.
Reviewed-by: Jason Gunthorpe jgg@mellanox.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/infiniband/core/umem.c | 2 +- drivers/infiniband/core/umem_odp.c | 13 ++++++------- drivers/infiniband/hw/hfi1/user_pages.c | 2 +- drivers/infiniband/hw/mthca/mthca_memfree.c | 2 +- drivers/infiniband/hw/qib/qib_user_pages.c | 2 +- drivers/infiniband/hw/qib/qib_user_sdma.c | 2 +- drivers/infiniband/hw/usnic/usnic_uiom.c | 2 +- drivers/infiniband/sw/siw/siw_mem.c | 2 +- 8 files changed, 13 insertions(+), 14 deletions(-)
diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c index 214e87aa609d..55daefaa9b88 100644 --- a/drivers/infiniband/core/umem.c +++ b/drivers/infiniband/core/umem.c @@ -266,7 +266,7 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr, sg = umem->sg_head.sgl;
while (npages) { - ret = get_user_pages_fast(cur_base, + ret = pin_user_pages_fast(cur_base, min_t(unsigned long, npages, PAGE_SIZE / sizeof(struct page *)), diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c index e42d44e501fd..abc3bb6578cc 100644 --- a/drivers/infiniband/core/umem_odp.c +++ b/drivers/infiniband/core/umem_odp.c @@ -308,9 +308,8 @@ EXPORT_SYMBOL(ib_umem_odp_release); * The function returns -EFAULT if the DMA mapping operation fails. It returns * -EAGAIN if a concurrent invalidation prevents us from updating the page. * - * The page is released via put_user_page even if the operation failed. For - * on-demand pinning, the page is released whenever it isn't stored in the - * umem. + * The page is released via put_page even if the operation failed. For on-demand + * pinning, the page is released whenever it isn't stored in the umem. */ static int ib_umem_odp_map_dma_single_page( struct ib_umem_odp *umem_odp, @@ -363,7 +362,7 @@ static int ib_umem_odp_map_dma_single_page( }
out: - put_user_page(page); + put_page(page); return ret; }
@@ -473,7 +472,7 @@ int ib_umem_odp_map_dma_pages(struct ib_umem_odp *umem_odp, u64 user_virt, ret = -EFAULT; break; } - put_user_page(local_page_list[j]); + put_page(local_page_list[j]); continue; }
@@ -500,8 +499,8 @@ int ib_umem_odp_map_dma_pages(struct ib_umem_odp *umem_odp, u64 user_virt, * ib_umem_odp_map_dma_single_page(). */ if (npages - (j + 1) > 0) - put_user_pages(&local_page_list[j+1], - npages - (j + 1)); + release_pages(&local_page_list[j+1], + npages - (j + 1)); break; } } diff --git a/drivers/infiniband/hw/hfi1/user_pages.c b/drivers/infiniband/hw/hfi1/user_pages.c index 469acb961fbd..9a94761765c0 100644 --- a/drivers/infiniband/hw/hfi1/user_pages.c +++ b/drivers/infiniband/hw/hfi1/user_pages.c @@ -106,7 +106,7 @@ int hfi1_acquire_user_pages(struct mm_struct *mm, unsigned long vaddr, size_t np int ret; unsigned int gup_flags = FOLL_LONGTERM | (writable ? FOLL_WRITE : 0);
- ret = get_user_pages_fast(vaddr, npages, gup_flags, pages); + ret = pin_user_pages_fast(vaddr, npages, gup_flags, pages); if (ret < 0) return ret;
diff --git a/drivers/infiniband/hw/mthca/mthca_memfree.c b/drivers/infiniband/hw/mthca/mthca_memfree.c index edccfd6e178f..8269ab040c21 100644 --- a/drivers/infiniband/hw/mthca/mthca_memfree.c +++ b/drivers/infiniband/hw/mthca/mthca_memfree.c @@ -472,7 +472,7 @@ int mthca_map_user_db(struct mthca_dev *dev, struct mthca_uar *uar, goto out; }
- ret = get_user_pages_fast(uaddr & PAGE_MASK, 1, + ret = pin_user_pages_fast(uaddr & PAGE_MASK, 1, FOLL_WRITE | FOLL_LONGTERM, pages); if (ret < 0) goto out; diff --git a/drivers/infiniband/hw/qib/qib_user_pages.c b/drivers/infiniband/hw/qib/qib_user_pages.c index 6bf764e41891..7fc4b5f81fcd 100644 --- a/drivers/infiniband/hw/qib/qib_user_pages.c +++ b/drivers/infiniband/hw/qib/qib_user_pages.c @@ -108,7 +108,7 @@ int qib_get_user_pages(unsigned long start_page, size_t num_pages,
down_read(¤t->mm->mmap_sem); for (got = 0; got < num_pages; got += ret) { - ret = get_user_pages(start_page + got * PAGE_SIZE, + ret = pin_user_pages(start_page + got * PAGE_SIZE, num_pages - got, FOLL_LONGTERM | FOLL_WRITE | FOLL_FORCE, p + got, NULL); diff --git a/drivers/infiniband/hw/qib/qib_user_sdma.c b/drivers/infiniband/hw/qib/qib_user_sdma.c index 05190edc2611..1a3cc2957e3a 100644 --- a/drivers/infiniband/hw/qib/qib_user_sdma.c +++ b/drivers/infiniband/hw/qib/qib_user_sdma.c @@ -670,7 +670,7 @@ static int qib_user_sdma_pin_pages(const struct qib_devdata *dd, else j = npages;
- ret = get_user_pages_fast(addr, j, FOLL_LONGTERM, pages); + ret = pin_user_pages_fast(addr, j, FOLL_LONGTERM, pages); if (ret != j) { i = 0; j = ret; diff --git a/drivers/infiniband/hw/usnic/usnic_uiom.c b/drivers/infiniband/hw/usnic/usnic_uiom.c index 62e6ffa9ad78..600896727d34 100644 --- a/drivers/infiniband/hw/usnic/usnic_uiom.c +++ b/drivers/infiniband/hw/usnic/usnic_uiom.c @@ -141,7 +141,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable, ret = 0;
while (npages) { - ret = get_user_pages(cur_base, + ret = pin_user_pages(cur_base, min_t(unsigned long, npages, PAGE_SIZE / sizeof(struct page *)), gup_flags | FOLL_LONGTERM, diff --git a/drivers/infiniband/sw/siw/siw_mem.c b/drivers/infiniband/sw/siw/siw_mem.c index e99983f07663..e53b07dcfed5 100644 --- a/drivers/infiniband/sw/siw/siw_mem.c +++ b/drivers/infiniband/sw/siw/siw_mem.c @@ -426,7 +426,7 @@ struct siw_umem *siw_umem_get(u64 start, u64 len, bool writable) while (nents) { struct page **plist = &umem->page_chunk[i].plist[got];
- rv = get_user_pages(first_page_va, nents, + rv = pin_user_pages(first_page_va, nents, foll_flags | FOLL_LONGTERM, plist, NULL); if (rv < 0)
Convert process_vm_access to use the new pin_user_pages_remote() call, which sets FOLL_PIN. Setting FOLL_PIN is now required for code that requires tracking of pinned pages.
Also, release the pages via put_user_page*().
Also, rename "pages" to "pinned_pages", as this makes for easier reading of process_vm_rw_single_vec().
Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Jérôme Glisse jglisse@redhat.com Reviewed-by: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- mm/process_vm_access.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-)
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c index 357aa7bef6c0..fd20ab675b85 100644 --- a/mm/process_vm_access.c +++ b/mm/process_vm_access.c @@ -42,12 +42,11 @@ static int process_vm_rw_pages(struct page **pages, if (copy > len) copy = len;
- if (vm_write) { + if (vm_write) copied = copy_page_from_iter(page, offset, copy, iter); - set_page_dirty_lock(page); - } else { + else copied = copy_page_to_iter(page, offset, copy, iter); - } + len -= copied; if (copied < copy && iov_iter_count(iter)) return -EFAULT; @@ -96,7 +95,7 @@ static int process_vm_rw_single_vec(unsigned long addr, flags |= FOLL_WRITE;
while (!rc && nr_pages && iov_iter_count(iter)) { - int pages = min(nr_pages, max_pages_per_loop); + int pinned_pages = min(nr_pages, max_pages_per_loop); int locked = 1; size_t bytes;
@@ -106,14 +105,15 @@ static int process_vm_rw_single_vec(unsigned long addr, * current/current->mm */ down_read(&mm->mmap_sem); - pages = get_user_pages_remote(task, mm, pa, pages, flags, - process_pages, NULL, &locked); + pinned_pages = pin_user_pages_remote(task, mm, pa, pinned_pages, + flags, process_pages, + NULL, &locked); if (locked) up_read(&mm->mmap_sem); - if (pages <= 0) + if (pinned_pages <= 0) return -EFAULT;
- bytes = pages * PAGE_SIZE - start_offset; + bytes = pinned_pages * PAGE_SIZE - start_offset; if (bytes > len) bytes = len;
@@ -122,10 +122,12 @@ static int process_vm_rw_single_vec(unsigned long addr, vm_write); len -= bytes; start_offset = 0; - nr_pages -= pages; - pa += pages * PAGE_SIZE; - while (pages) - put_page(process_pages[--pages]); + nr_pages -= pinned_pages; + pa += pinned_pages * PAGE_SIZE; + + /* If vm_write is set, the pages need to be made dirty: */ + put_user_pages_dirty_lock(process_pages, pinned_pages, + vm_write); }
return rc;
Convert drm/via to use the new pin_user_pages_fast() call, which sets FOLL_PIN. Setting FOLL_PIN is now required for code that requires tracking of pinned pages, and therefore for any code that calls put_user_page().
In partial anticipation of this work, the drm/via driver was already calling put_user_page() instead of put_page(). Therefore, in order to convert from the get_user_pages()/put_page() model, to the pin_user_pages()/put_user_page() model, the only change required is to change get_user_pages() to pin_user_pages().
Acked-by: Daniel Vetter daniel.vetter@ffwll.ch Reviewed-by: Jérôme Glisse jglisse@redhat.com Reviewed-by: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/gpu/drm/via/via_dmablit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/via/via_dmablit.c b/drivers/gpu/drm/via/via_dmablit.c index 3db000aacd26..37c5e572993a 100644 --- a/drivers/gpu/drm/via/via_dmablit.c +++ b/drivers/gpu/drm/via/via_dmablit.c @@ -239,7 +239,7 @@ via_lock_all_dma_pages(drm_via_sg_info_t *vsg, drm_via_dmablit_t *xfer) vsg->pages = vzalloc(array_size(sizeof(struct page *), vsg->num_pages)); if (NULL == vsg->pages) return -ENOMEM; - ret = get_user_pages_fast((unsigned long)xfer->mem_addr, + ret = pin_user_pages_fast((unsigned long)xfer->mem_addr, vsg->num_pages, vsg->direction == DMA_FROM_DEVICE ? FOLL_WRITE : 0, vsg->pages);
Convert fs/io_uring to use the new pin_user_pages() call, which sets FOLL_PIN. Setting FOLL_PIN is now required for code that requires tracking of pinned pages, and therefore for any code that calls put_user_page().
In partial anticipation of this work, the io_uring code was already calling put_user_page() instead of put_page(). Therefore, in order to convert from the get_user_pages()/put_page() model, to the pin_user_pages()/put_user_page() model, the only change required here is to change get_user_pages() to pin_user_pages().
Reviewed-by: Jens Axboe axboe@kernel.dk Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: John Hubbard jhubbard@nvidia.com --- fs/io_uring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index 562e3a1a1bf9..9f804cb25c61 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4815,7 +4815,7 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, void __user *arg,
ret = 0; down_read(¤t->mm->mmap_sem); - pret = get_user_pages(ubuf, nr_pages, + pret = pin_user_pages(ubuf, nr_pages, FOLL_WRITE | FOLL_LONGTERM, pages, vmas); if (pret == nr_pages) {
Convert net/xdp to use the new pin_longterm_pages() call, which sets FOLL_PIN. Setting FOLL_PIN is now required for code that requires tracking of pinned pages.
In partial anticipation of this work, the net/xdp code was already calling put_user_page() instead of put_page(). Therefore, in order to convert from the get_user_pages()/put_page() model, to the pin_user_pages()/put_user_page() model, the only change required here is to change get_user_pages() to pin_user_pages().
Acked-by: Björn Töpel bjorn.topel@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- net/xdp/xdp_umem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c index 3049af269fbf..d071003b5e76 100644 --- a/net/xdp/xdp_umem.c +++ b/net/xdp/xdp_umem.c @@ -291,7 +291,7 @@ static int xdp_umem_pin_pages(struct xdp_umem *umem) return -ENOMEM;
down_read(¤t->mm->mmap_sem); - npgs = get_user_pages(umem->address, umem->npgs, + npgs = pin_user_pages(umem->address, umem->npgs, gup_flags | FOLL_LONGTERM, &umem->pgs[0], NULL); up_read(¤t->mm->mmap_sem);
1. Change v4l2 from get_user_pages() to pin_user_pages().
2. Because all FOLL_PIN-acquired pages must be released via put_user_page(), also convert the put_page() call over to put_user_pages_dirty_lock().
Acked-by: Hans Verkuil hverkuil-cisco@xs4all.nl Cc: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/media/v4l2-core/videobuf-dma-sg.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c index 28262190c3ab..162a2633b1e3 100644 --- a/drivers/media/v4l2-core/videobuf-dma-sg.c +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c @@ -183,12 +183,12 @@ static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma, dprintk(1, "init user [0x%lx+0x%lx => %d pages]\n", data, size, dma->nr_pages);
- err = get_user_pages(data & PAGE_MASK, dma->nr_pages, + err = pin_user_pages(data & PAGE_MASK, dma->nr_pages, flags | FOLL_LONGTERM, dma->pages, NULL);
if (err != dma->nr_pages) { dma->nr_pages = (err >= 0) ? err : 0; - dprintk(1, "get_user_pages: err=%d [%d]\n", err, + dprintk(1, "pin_user_pages: err=%d [%d]\n", err, dma->nr_pages); return err < 0 ? err : -EINVAL; } @@ -349,11 +349,8 @@ int videobuf_dma_free(struct videobuf_dmabuf *dma) BUG_ON(dma->sglen);
if (dma->pages) { - for (i = 0; i < dma->nr_pages; i++) { - if (dma->direction == DMA_FROM_DEVICE) - set_page_dirty_lock(dma->pages[i]); - put_page(dma->pages[i]); - } + put_user_pages_dirty_lock(dma->pages, dma->nr_pages, + dma->direction == DMA_FROM_DEVICE); kfree(dma->pages); dma->pages = NULL; }
1. Change vfio from get_user_pages_remote(), to pin_user_pages_remote().
2. Because all FOLL_PIN-acquired pages must be released via put_user_page(), also convert the put_page() call over to put_user_pages_dirty_lock().
Note that this effectively changes the code's behavior in vfio_iommu_type1.c: put_pfn(): it now ultimately calls set_page_dirty_lock(), instead of set_page_dirty(). This is probably more accurate.
As Christoph Hellwig put it, "set_page_dirty() is only safe if we are dealing with a file backed page where we have reference on the inode it hangs off." [1]
[1] https://lore.kernel.org/r/20190723153640.GB720@lst.de
Tested-by: Alex Williamson alex.williamson@redhat.com Acked-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- drivers/vfio/vfio_iommu_type1.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index b800fc9a0251..18bfc2fc8e6d 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -309,9 +309,8 @@ static int put_pfn(unsigned long pfn, int prot) { if (!is_invalid_reserved_pfn(pfn)) { struct page *page = pfn_to_page(pfn); - if (prot & IOMMU_WRITE) - SetPageDirty(page); - put_page(page); + + put_user_pages_dirty_lock(&page, 1, prot & IOMMU_WRITE); return 1; } return 0; @@ -329,7 +328,7 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, flags |= FOLL_WRITE;
down_read(&mm->mmap_sem); - ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags | FOLL_LONGTERM, + ret = pin_user_pages_remote(NULL, mm, vaddr, 1, flags | FOLL_LONGTERM, page, NULL, NULL); if (ret == 1) { *pfn = page_to_pfn(page[0]);
1. Convert from get_user_pages() to pin_user_pages().
2. As required by pin_user_pages(), release these pages via put_user_page().
Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: John Hubbard jhubbard@nvidia.com --- arch/powerpc/mm/book3s64/iommu_api.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c index 56cc84520577..a86547822034 100644 --- a/arch/powerpc/mm/book3s64/iommu_api.c +++ b/arch/powerpc/mm/book3s64/iommu_api.c @@ -103,7 +103,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua, for (entry = 0; entry < entries; entry += chunk) { unsigned long n = min(entries - entry, chunk);
- ret = get_user_pages(ua + (entry << PAGE_SHIFT), n, + ret = pin_user_pages(ua + (entry << PAGE_SHIFT), n, FOLL_WRITE | FOLL_LONGTERM, mem->hpages + entry, NULL); if (ret == n) { @@ -167,9 +167,8 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua, return 0;
free_exit: - /* free the reference taken */ - for (i = 0; i < pinned; i++) - put_page(mem->hpages[i]); + /* free the references taken */ + put_user_pages(mem->hpages, pinned);
vfree(mem->hpas); kfree(mem); @@ -215,7 +214,8 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem) if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY) SetPageDirty(page);
- put_page(page); + put_user_page(page); + mem->hpas[i] = 0; } }
Fix the gup benchmark flags to use the symbolic FOLL_WRITE, instead of a hard-coded "1" value.
Also, clean up the filtering of gup flags a little, by just doing it once before issuing any of the get_user_pages*() calls. This makes it harder to overlook, instead of having little "gup_flags & 1" phrases in the function calls.
Reviewed-by: Ira Weiny ira.weiny@intel.com Signed-off-by: John Hubbard jhubbard@nvidia.com --- mm/gup_benchmark.c | 9 ++++++--- tools/testing/selftests/vm/gup_benchmark.c | 6 +++++- 2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c index ad9d5b1c4473..8dba38e79a9f 100644 --- a/mm/gup_benchmark.c +++ b/mm/gup_benchmark.c @@ -49,18 +49,21 @@ static int __gup_benchmark_ioctl(unsigned int cmd, nr = (next - addr) / PAGE_SIZE; }
+ /* Filter out most gup flags: only allow a tiny subset here: */ + gup->flags &= FOLL_WRITE; + switch (cmd) { case GUP_FAST_BENCHMARK: - nr = get_user_pages_fast(addr, nr, gup->flags & 1, + nr = get_user_pages_fast(addr, nr, gup->flags, pages + i); break; case GUP_LONGTERM_BENCHMARK: nr = get_user_pages(addr, nr, - (gup->flags & 1) | FOLL_LONGTERM, + gup->flags | FOLL_LONGTERM, pages + i, NULL); break; case GUP_BENCHMARK: - nr = get_user_pages(addr, nr, gup->flags & 1, pages + i, + nr = get_user_pages(addr, nr, gup->flags, pages + i, NULL); break; default: diff --git a/tools/testing/selftests/vm/gup_benchmark.c b/tools/testing/selftests/vm/gup_benchmark.c index 485cf06ef013..389327e9b30a 100644 --- a/tools/testing/selftests/vm/gup_benchmark.c +++ b/tools/testing/selftests/vm/gup_benchmark.c @@ -18,6 +18,9 @@ #define GUP_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark) #define GUP_BENCHMARK _IOWR('g', 3, struct gup_benchmark)
+/* Just the flags we need, copied from mm.h: */ +#define FOLL_WRITE 0x01 /* check pte is writable */ + struct gup_benchmark { __u64 get_delta_usec; __u64 put_delta_usec; @@ -85,7 +88,8 @@ int main(int argc, char **argv) }
gup.nr_pages_per_call = nr_pages; - gup.flags = write; + if (write) + gup.flags |= FOLL_WRITE;
fd = open("/sys/kernel/debug/gup_benchmark", O_RDWR); if (fd == -1)
In order to provide a clearer, more symmetric API for pinning and unpinning DMA pages. This way, pin_user_pages*() calls match up with unpin_user_pages*() calls, and the API is a lot closer to being self-explanatory.
Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: John Hubbard jhubbard@nvidia.com --- Documentation/core-api/pin_user_pages.rst | 2 +- arch/powerpc/mm/book3s64/iommu_api.c | 4 +-- drivers/gpu/drm/via/via_dmablit.c | 4 +-- drivers/infiniband/core/umem.c | 2 +- drivers/infiniband/hw/hfi1/user_pages.c | 2 +- drivers/infiniband/hw/mthca/mthca_memfree.c | 6 ++-- drivers/infiniband/hw/qib/qib_user_pages.c | 2 +- drivers/infiniband/hw/qib/qib_user_sdma.c | 6 ++-- drivers/infiniband/hw/usnic/usnic_uiom.c | 2 +- drivers/infiniband/sw/siw/siw_mem.c | 2 +- drivers/media/v4l2-core/videobuf-dma-sg.c | 4 +-- drivers/platform/goldfish/goldfish_pipe.c | 4 +-- drivers/vfio/vfio_iommu_type1.c | 2 +- fs/io_uring.c | 4 +-- include/linux/mm.h | 26 ++++++++--------- mm/gup.c | 32 ++++++++++----------- mm/process_vm_access.c | 4 +-- net/xdp/xdp_umem.c | 2 +- 18 files changed, 55 insertions(+), 55 deletions(-)
diff --git a/Documentation/core-api/pin_user_pages.rst b/Documentation/core-api/pin_user_pages.rst index 71849830cd48..1d490155ecd7 100644 --- a/Documentation/core-api/pin_user_pages.rst +++ b/Documentation/core-api/pin_user_pages.rst @@ -219,7 +219,7 @@ since the system was booted, via two new /proc/vmstat entries: :: /proc/vmstat/nr_foll_pin_requested
Those are both going to show zero, unless CONFIG_DEBUG_VM is set. This is -because there is a noticeable performance drop in put_user_page(), when they +because there is a noticeable performance drop in unpin_user_page(), when they are activated.
References diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c index a86547822034..eba73ebd8ae5 100644 --- a/arch/powerpc/mm/book3s64/iommu_api.c +++ b/arch/powerpc/mm/book3s64/iommu_api.c @@ -168,7 +168,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
free_exit: /* free the references taken */ - put_user_pages(mem->hpages, pinned); + unpin_user_pages(mem->hpages, pinned);
vfree(mem->hpas); kfree(mem); @@ -214,7 +214,7 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem) if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY) SetPageDirty(page);
- put_user_page(page); + unpin_user_page(page);
mem->hpas[i] = 0; } diff --git a/drivers/gpu/drm/via/via_dmablit.c b/drivers/gpu/drm/via/via_dmablit.c index 37c5e572993a..719d036c9384 100644 --- a/drivers/gpu/drm/via/via_dmablit.c +++ b/drivers/gpu/drm/via/via_dmablit.c @@ -188,8 +188,8 @@ via_free_sg_info(struct pci_dev *pdev, drm_via_sg_info_t *vsg) kfree(vsg->desc_pages); /* fall through */ case dr_via_pages_locked: - put_user_pages_dirty_lock(vsg->pages, vsg->num_pages, - (vsg->direction == DMA_FROM_DEVICE)); + unpin_user_pages_dirty_lock(vsg->pages, vsg->num_pages, + (vsg->direction == DMA_FROM_DEVICE)); /* fall through */ case dr_via_pages_alloc: vfree(vsg->pages); diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c index 55daefaa9b88..a6094766b6f5 100644 --- a/drivers/infiniband/core/umem.c +++ b/drivers/infiniband/core/umem.c @@ -54,7 +54,7 @@ static void __ib_umem_release(struct ib_device *dev, struct ib_umem *umem, int d
for_each_sg_page(umem->sg_head.sgl, &sg_iter, umem->sg_nents, 0) { page = sg_page_iter_page(&sg_iter); - put_user_pages_dirty_lock(&page, 1, umem->writable && dirty); + unpin_user_pages_dirty_lock(&page, 1, umem->writable && dirty); }
sg_free_table(&umem->sg_head); diff --git a/drivers/infiniband/hw/hfi1/user_pages.c b/drivers/infiniband/hw/hfi1/user_pages.c index 9a94761765c0..3b505006c0a6 100644 --- a/drivers/infiniband/hw/hfi1/user_pages.c +++ b/drivers/infiniband/hw/hfi1/user_pages.c @@ -118,7 +118,7 @@ int hfi1_acquire_user_pages(struct mm_struct *mm, unsigned long vaddr, size_t np void hfi1_release_user_pages(struct mm_struct *mm, struct page **p, size_t npages, bool dirty) { - put_user_pages_dirty_lock(p, npages, dirty); + unpin_user_pages_dirty_lock(p, npages, dirty);
if (mm) { /* during close after signal, mm can be NULL */ atomic64_sub(npages, &mm->pinned_vm); diff --git a/drivers/infiniband/hw/mthca/mthca_memfree.c b/drivers/infiniband/hw/mthca/mthca_memfree.c index 8269ab040c21..78a48aea3faf 100644 --- a/drivers/infiniband/hw/mthca/mthca_memfree.c +++ b/drivers/infiniband/hw/mthca/mthca_memfree.c @@ -482,7 +482,7 @@ int mthca_map_user_db(struct mthca_dev *dev, struct mthca_uar *uar,
ret = pci_map_sg(dev->pdev, &db_tab->page[i].mem, 1, PCI_DMA_TODEVICE); if (ret < 0) { - put_user_page(pages[0]); + unpin_user_page(pages[0]); goto out; }
@@ -490,7 +490,7 @@ int mthca_map_user_db(struct mthca_dev *dev, struct mthca_uar *uar, mthca_uarc_virt(dev, uar, i)); if (ret) { pci_unmap_sg(dev->pdev, &db_tab->page[i].mem, 1, PCI_DMA_TODEVICE); - put_user_page(sg_page(&db_tab->page[i].mem)); + unpin_user_page(sg_page(&db_tab->page[i].mem)); goto out; }
@@ -556,7 +556,7 @@ void mthca_cleanup_user_db_tab(struct mthca_dev *dev, struct mthca_uar *uar, if (db_tab->page[i].uvirt) { mthca_UNMAP_ICM(dev, mthca_uarc_virt(dev, uar, i), 1); pci_unmap_sg(dev->pdev, &db_tab->page[i].mem, 1, PCI_DMA_TODEVICE); - put_user_page(sg_page(&db_tab->page[i].mem)); + unpin_user_page(sg_page(&db_tab->page[i].mem)); } }
diff --git a/drivers/infiniband/hw/qib/qib_user_pages.c b/drivers/infiniband/hw/qib/qib_user_pages.c index 7fc4b5f81fcd..342e3172ca40 100644 --- a/drivers/infiniband/hw/qib/qib_user_pages.c +++ b/drivers/infiniband/hw/qib/qib_user_pages.c @@ -40,7 +40,7 @@ static void __qib_release_user_pages(struct page **p, size_t num_pages, int dirty) { - put_user_pages_dirty_lock(p, num_pages, dirty); + unpin_user_pages_dirty_lock(p, num_pages, dirty); }
/** diff --git a/drivers/infiniband/hw/qib/qib_user_sdma.c b/drivers/infiniband/hw/qib/qib_user_sdma.c index 1a3cc2957e3a..a67599b5a550 100644 --- a/drivers/infiniband/hw/qib/qib_user_sdma.c +++ b/drivers/infiniband/hw/qib/qib_user_sdma.c @@ -317,7 +317,7 @@ static int qib_user_sdma_page_to_frags(const struct qib_devdata *dd, * the caller can ignore this page. */ if (put) { - put_user_page(page); + unpin_user_page(page); } else { /* coalesce case */ kunmap(page); @@ -631,7 +631,7 @@ static void qib_user_sdma_free_pkt_frag(struct device *dev, kunmap(pkt->addr[i].page);
if (pkt->addr[i].put_page) - put_user_page(pkt->addr[i].page); + unpin_user_page(pkt->addr[i].page); else __free_page(pkt->addr[i].page); } else if (pkt->addr[i].kvaddr) { @@ -706,7 +706,7 @@ static int qib_user_sdma_pin_pages(const struct qib_devdata *dd, /* if error, return all pages not managed by pkt */ free_pages: while (i < j) - put_user_page(pages[i++]); + unpin_user_page(pages[i++]);
done: return ret; diff --git a/drivers/infiniband/hw/usnic/usnic_uiom.c b/drivers/infiniband/hw/usnic/usnic_uiom.c index 600896727d34..bd9f944b68fc 100644 --- a/drivers/infiniband/hw/usnic/usnic_uiom.c +++ b/drivers/infiniband/hw/usnic/usnic_uiom.c @@ -75,7 +75,7 @@ static void usnic_uiom_put_pages(struct list_head *chunk_list, int dirty) for_each_sg(chunk->page_list, sg, chunk->nents, i) { page = sg_page(sg); pa = sg_phys(sg); - put_user_pages_dirty_lock(&page, 1, dirty); + unpin_user_pages_dirty_lock(&page, 1, dirty); usnic_dbg("pa: %pa\n", &pa); } kfree(chunk); diff --git a/drivers/infiniband/sw/siw/siw_mem.c b/drivers/infiniband/sw/siw/siw_mem.c index e53b07dcfed5..e2061dc0b043 100644 --- a/drivers/infiniband/sw/siw/siw_mem.c +++ b/drivers/infiniband/sw/siw/siw_mem.c @@ -63,7 +63,7 @@ struct siw_mem *siw_mem_id2obj(struct siw_device *sdev, int stag_index) static void siw_free_plist(struct siw_page_chunk *chunk, int num_pages, bool dirty) { - put_user_pages_dirty_lock(chunk->plist, num_pages, dirty); + unpin_user_pages_dirty_lock(chunk->plist, num_pages, dirty); }
void siw_umem_release(struct siw_umem *umem, bool dirty) diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c index 162a2633b1e3..13b65ed9e74c 100644 --- a/drivers/media/v4l2-core/videobuf-dma-sg.c +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c @@ -349,8 +349,8 @@ int videobuf_dma_free(struct videobuf_dmabuf *dma) BUG_ON(dma->sglen);
if (dma->pages) { - put_user_pages_dirty_lock(dma->pages, dma->nr_pages, - dma->direction == DMA_FROM_DEVICE); + unpin_user_pages_dirty_lock(dma->pages, dma->nr_pages, + dma->direction == DMA_FROM_DEVICE); kfree(dma->pages); dma->pages = NULL; } diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c index 2a5901efecde..1ab207ec9c94 100644 --- a/drivers/platform/goldfish/goldfish_pipe.c +++ b/drivers/platform/goldfish/goldfish_pipe.c @@ -360,8 +360,8 @@ static int transfer_max_buffers(struct goldfish_pipe *pipe,
*consumed_size = pipe->command_buffer->rw_params.consumed_size;
- put_user_pages_dirty_lock(pipe->pages, pages_count, - !is_write && *consumed_size > 0); + unpin_user_pages_dirty_lock(pipe->pages, pages_count, + !is_write && *consumed_size > 0);
mutex_unlock(&pipe->lock); return 0; diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 18bfc2fc8e6d..a177bf2c6683 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -310,7 +310,7 @@ static int put_pfn(unsigned long pfn, int prot) if (!is_invalid_reserved_pfn(pfn)) { struct page *page = pfn_to_page(pfn);
- put_user_pages_dirty_lock(&page, 1, prot & IOMMU_WRITE); + unpin_user_pages_dirty_lock(&page, 1, prot & IOMMU_WRITE); return 1; } return 0; diff --git a/fs/io_uring.c b/fs/io_uring.c index 9f804cb25c61..87618e3c05ea 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4694,7 +4694,7 @@ static int io_sqe_buffer_unregister(struct io_ring_ctx *ctx) struct io_mapped_ubuf *imu = &ctx->user_bufs[i];
for (j = 0; j < imu->nr_bvecs; j++) - put_user_page(imu->bvec[j].bv_page); + unpin_user_page(imu->bvec[j].bv_page);
if (ctx->account_mem) io_unaccount_mem(ctx->user, imu->nr_bvecs); @@ -4839,7 +4839,7 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, void __user *arg, * release any pages we did get */ if (pret > 0) - put_user_pages(pages, pret); + unpin_user_pages(pages, pret); if (ctx->account_mem) io_unaccount_mem(ctx->user, nr_pages); kvfree(imu->bvec); diff --git a/include/linux/mm.h b/include/linux/mm.h index f9653e666bf4..0ede06a15eea 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1044,27 +1044,27 @@ static inline void put_page(struct page *page) }
/** - * put_user_page() - release a gup-pinned page + * unpin_user_page() - release a gup-pinned page * @page: pointer to page to be released * * Pages that were pinned via pin_user_pages*() must be released via either - * put_user_page(), or one of the put_user_pages*() routines. This is so that - * eventually such pages can be separately tracked and uniquely handled. In + * unpin_user_page(), or one of the unpin_user_pages*() routines. This is so + * that eventually such pages can be separately tracked and uniquely handled. In * particular, interactions with RDMA and filesystems need special handling. * - * put_user_page() and put_page() are not interchangeable, despite this early - * implementation that makes them look the same. put_user_page() calls must + * unpin_user_page() and put_page() are not interchangeable, despite this early + * implementation that makes them look the same. unpin_user_page() calls must * be perfectly matched up with pin*() calls. */ -static inline void put_user_page(struct page *page) +static inline void unpin_user_page(struct page *page) { put_page(page); }
-void put_user_pages_dirty_lock(struct page **pages, unsigned long npages, - bool make_dirty); +void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, + bool make_dirty);
-void put_user_pages(struct page **pages, unsigned long npages); +void unpin_user_pages(struct page **pages, unsigned long npages);
#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) #define SECTION_IN_PAGE_FLAGS @@ -2594,7 +2594,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, #define FOLL_ANON 0x8000 /* don't do file mappings */ #define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see below */ #define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */ -#define FOLL_PIN 0x40000 /* pages must be released via put_user_page() */ +#define FOLL_PIN 0x40000 /* pages must be released via unpin_user_page */
/* * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each @@ -2629,7 +2629,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, * Direct IO). This lets the filesystem know that some non-file-system entity is * potentially changing the pages' data. In contrast to FOLL_GET (whose pages * are released via put_page()), FOLL_PIN pages must be released, ultimately, by - * a call to put_user_page(). + * a call to unpin_user_page(). * * FOLL_PIN is similar to FOLL_GET: both of these pin pages. They use different * and separate refcounting mechanisms, however, and that means that each has @@ -2637,7 +2637,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, * * FOLL_GET: get_user_pages*() to acquire, and put_page() to release. * - * FOLL_PIN: pin_user_pages*() to acquire, and put_user_pages to release. + * FOLL_PIN: pin_user_pages*() to acquire, and unpin_user_pages to release. * * FOLL_PIN and FOLL_GET are mutually exclusive for a given function call. * (The underlying pages may experience both FOLL_GET-based and FOLL_PIN-based @@ -2647,7 +2647,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, * FOLL_PIN should be set internally by the pin_user_pages*() APIs, never * directly by the caller. That's in order to help avoid mismatches when * releasing pages: get_user_pages*() pages must be released via put_page(), - * while pin_user_pages*() pages must be released via put_user_page(). + * while pin_user_pages*() pages must be released via unpin_user_page(). * * Please see Documentation/vm/pin_user_pages.rst for more information. */ diff --git a/mm/gup.c b/mm/gup.c index 1c200eeabd77..b8079d22c0be 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -45,7 +45,7 @@ static inline struct page *try_get_compound_head(struct page *page, int refs) }
/** - * put_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages + * unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages * @pages: array of pages to be maybe marked dirty, and definitely released. * @npages: number of pages in the @pages array. * @make_dirty: whether to mark the pages dirty @@ -55,19 +55,19 @@ static inline struct page *try_get_compound_head(struct page *page, int refs) * * For each page in the @pages array, make that page (or its head page, if a * compound page) dirty, if @make_dirty is true, and if the page was previously - * listed as clean. In any case, releases all pages using put_user_page(), - * possibly via put_user_pages(), for the non-dirty case. + * listed as clean. In any case, releases all pages using unpin_user_page(), + * possibly via unpin_user_pages(), for the non-dirty case. * - * Please see the put_user_page() documentation for details. + * Please see the unpin_user_page() documentation for details. * * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is * required, then the caller should a) verify that this is really correct, * because _lock() is usually required, and b) hand code it: - * set_page_dirty_lock(), put_user_page(). + * set_page_dirty_lock(), unpin_user_page(). * */ -void put_user_pages_dirty_lock(struct page **pages, unsigned long npages, - bool make_dirty) +void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, + bool make_dirty) { unsigned long index;
@@ -78,7 +78,7 @@ void put_user_pages_dirty_lock(struct page **pages, unsigned long npages, */
if (!make_dirty) { - put_user_pages(pages, npages); + unpin_user_pages(pages, npages); return; }
@@ -106,21 +106,21 @@ void put_user_pages_dirty_lock(struct page **pages, unsigned long npages, */ if (!PageDirty(page)) set_page_dirty_lock(page); - put_user_page(page); + unpin_user_page(page); } } -EXPORT_SYMBOL(put_user_pages_dirty_lock); +EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
/** - * put_user_pages() - release an array of gup-pinned pages. + * unpin_user_pages() - release an array of gup-pinned pages. * @pages: array of pages to be marked dirty and released. * @npages: number of pages in the @pages array. * - * For each page in the @pages array, release the page using put_user_page(). + * For each page in the @pages array, release the page using unpin_user_page(). * - * Please see the put_user_page() documentation for details. + * Please see the unpin_user_page() documentation for details. */ -void put_user_pages(struct page **pages, unsigned long npages) +void unpin_user_pages(struct page **pages, unsigned long npages) { unsigned long index;
@@ -130,9 +130,9 @@ void put_user_pages(struct page **pages, unsigned long npages) * single operation to the head page should suffice. */ for (index = 0; index < npages; index++) - put_user_page(pages[index]); + unpin_user_page(pages[index]); } -EXPORT_SYMBOL(put_user_pages); +EXPORT_SYMBOL(unpin_user_pages);
#ifdef CONFIG_MMU static struct page *no_page_table(struct vm_area_struct *vma, diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c index fd20ab675b85..de41e830cdac 100644 --- a/mm/process_vm_access.c +++ b/mm/process_vm_access.c @@ -126,8 +126,8 @@ static int process_vm_rw_single_vec(unsigned long addr, pa += pinned_pages * PAGE_SIZE;
/* If vm_write is set, the pages need to be made dirty: */ - put_user_pages_dirty_lock(process_pages, pinned_pages, - vm_write); + unpin_user_pages_dirty_lock(process_pages, pinned_pages, + vm_write); }
return rc; diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c index d071003b5e76..ac182c38f7b0 100644 --- a/net/xdp/xdp_umem.c +++ b/net/xdp/xdp_umem.c @@ -212,7 +212,7 @@ static int xdp_umem_map_pages(struct xdp_umem *umem)
static void xdp_umem_unpin_pages(struct xdp_umem *umem) { - put_user_pages_dirty_lock(umem->pgs, umem->npgs, true); + unpin_user_pages_dirty_lock(umem->pgs, umem->npgs, true);
kfree(umem->pgs); umem->pgs = NULL;
Looks sensible:
Reviewed-by: Christoph Hellwig hch@lst.de
On 1/7/20 2:45 PM, John Hubbard wrote:
Hi,
The "track FOLL_PIN pages" would have been the very next patch, but it is not included here because I'm still debugging a bug report from Leon. Let's get all of the prerequisite work (it's been reviewed) into the tree so that future reviews are easier. It's clear that any fixes that are required to the tracking patch, won't affect these patches here.
This implements an API naming change (put_user_page*() --> unpin_user_page*()), and also adds FOLL_PIN page support, up to *but not including* actually tracking FOLL_PIN pages. It extends the FOLL_PIN support to a few select subsystems. More subsystems will be added in follow up work.
Hi Andrew and all,
To clarify: I'm hoping that this series can go into 5.6.
Meanwhile, I'm working on tracking down and solving the problem that Leon reported, in the "track FOLL_PIN pages" patch, and that patch is not part of this series.
thanks,
On 1/9/20 2:07 PM, John Hubbard wrote:
On 1/7/20 2:45 PM, John Hubbard wrote:
Hi,
The "track FOLL_PIN pages" would have been the very next patch, but it is not included here because I'm still debugging a bug report from Leon. Let's get all of the prerequisite work (it's been reviewed) into the tree so that future reviews are easier. It's clear that any fixes that are required to the tracking patch, won't affect these patches here.
This implements an API naming change (put_user_page*() --> unpin_user_page*()), and also adds FOLL_PIN page support, up to *but not including* actually tracking FOLL_PIN pages. It extends the FOLL_PIN support to a few select subsystems. More subsystems will be added in follow up work.
Hi Andrew and all,
To clarify: I'm hoping that this series can go into 5.6.
Meanwhile, I'm working on tracking down and solving the problem that Leon reported, in the "track FOLL_PIN pages" patch, and that patch is not part of this series.
Hi Andrew and all,
Any thoughts on this?
As for the not-included-yet tracking patch, my local testing still suggests the need to allow for larger refcounts of huge pages (in other words, I can write a test to pin huge pages many times, and overflow with the same backtrace that Leon has reported).
The second struct page (I recall Jan suggested) can hold those, so I'm going to proceed with that approach, while waiting to see if Leon has any more test data for me.
Again, I think this series is worth getting out of the way, in the meantime.
thanks,
On Tue, 14 Jan 2020 12:15:08 -0800 John Hubbard jhubbard@nvidia.com wrote:
Hi Andrew and all,
To clarify: I'm hoping that this series can go into 5.6.
Meanwhile, I'm working on tracking down and solving the problem that Leon reported, in the "track FOLL_PIN pages" patch, and that patch is not part of this series.
Hi Andrew and all,
Any thoughts on this?
5.6 is late. But it was in -mm before (briefly) and appears to be mature and well-reviewed.
I'll toss it in there and shall push it into -next hopefully today. Let's decide 2-3 weeks hence.
linux-kselftest-mirror@lists.linaro.org
-
Andrew Morton -
Christoph Hellwig -
John Hubbard