OK, here we go. Any VFIO and Infiniband runtime testing from anyone, is especially welcome here.
Changes since v3:
* VFIO fix (patch 8): applied further cleanup: removed a pre-existing, unnecessary release and reacquire of mmap_sem. Moved the DAX vma checks from the vfio call site, to gup internals, and added comments (and commit log) to clarify.
* Due to the above, made a corresponding fix to the pin_longterm_pages_remote(), which was actually calling the wrong gup internal function.
* Changed put_user_page() comments, to refer to pin*() APIs, rather than get_user_pages*() APIs.
* Reverted an accidental whitespace-only change in the IB ODP code.
* Added a few more reviewed-by tags.
Changes since v2:
* Added a patch to convert IB/umem from normal gup, to gup_fast(). This is also posted separately, in order to hopefully get some runtime testing.
* Changed the page devmap code to be a little clearer, thanks to Jerome for that.
* Split out the page devmap changes into a separate patch (and moved Ira's Signed-off-by to that patch).
* Fixed my bug in IB: ODP code does not require pin_user_pages() semantics. Therefore, revert the put_user_page() calls to put_page(), and leave the get_user_pages() call as-is.
* As part of the revert, I am proposing here a change directly from put_user_pages(), to release_pages(). I'd feel better if someone agrees that this is the best way. It uses the more efficient release_pages(), instead of put_page() in a loop, and keep the change to just a few character on one line, but OTOH it is not a pure revert.
* Loosened the FOLL_LONGTERM restrictions in the __get_user_pages_locked() implementation, and used that in order to fix up a VFIO bug. Thanks to Jason for that idea.
* Note the use of release_pages() in IB: is that OK?
* Added a few more WARN's and clarifying comments nearby.
* Many documentation improvements in various comments.
* Moved the new pin_user_pages.rst from Documentation/vm/ to Documentation/core-api/ .
* Commit descriptions: added clarifying notes to the three patches (drm/via, fs/io_uring, net/xdp) that already had put_user_page() calls in place.
* Collected all pending Reviewed-by and Acked-by tags, from v1 and v2 email threads.
* Lot of churn from v2 --> v3, so it's possible that new bugs sneaked in.
NOT DONE: separate patchset is required:
* __get_user_pages_locked(): stop compensating for buggy callers who failed to set FOLL_GET. Instead, assert that FOLL_GET is set (and fail if it's not).
====================================================================== Original cover letter (edited to fix up the patch description numbers)
This applies cleanly to linux-next and mmotm, and also to linux.git if linux-next's commit 20cac10710c9 ("mm/gup_benchmark: fix MAP_HUGETLB case") is first applied there.
This provides tracking of dma-pinned pages. This is a prerequisite to solving the larger 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) put_user_page()
Because there are interdependencies with FOLL_LONGTERM, a similar conversion as for FOLL_PIN, was applied. The change was from this:
get_user_pages(FOLL_LONGTERM) (also sets FOLL_GET) put_page()
to this: pin_longterm_pages() (sets FOLL_PIN | FOLL_LONGTERM) put_user_page()
============================================================ Patch summary:
* Patches 1-8: refactoring and preparatory cleanup, independent fixes
* Patch 9: introduce pin_user_pages(), FOLL_PIN, but no functional changes yet * Patches 10-15: Convert existing put_user_page() callers, to use the new pin*() * Patch 16: Activate tracking of FOLL_PIN pages. * Patches 17-19: convert FOLL_LONGTERM callers * Patches: 20-22: gup_benchmark and run_vmtests support * Patch 23: enforce FOLL_LONGTERM as a gup-internal (only) flag
============================================================ 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.
Also, my runtime testing for the call sites so far is very weak:
* 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 (still only have crude "IB pingpong" working, on a good day: it's not exercising my conversions at runtime...) * 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...
============================================================ Next:
* Get the block/bio_vec sites converted to use pin_user_pages().
* Work with Ira and Dave Chinner to weave this together with the layout lease stuff.
============================================================
[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/
John Hubbard (23): mm/gup: pass flags arg to __gup_device_* functions 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 IB/umem: use get_user_pages_fast() to pin DMA pages media/v4l2-core: set pages dirty upon releasing DMA buffers vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM 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, FOLL_LONGTERM via pin_longterm_pages*() 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() mm/gup: track FOLL_PIN pages media/v4l2-core: pin_longterm_pages (FOLL_PIN) and put_user_page() conversion vfio, mm: pin_longterm_pages (FOLL_PIN) and put_user_page() conversion powerpc: book3s64: convert to pin_longterm_pages() and put_user_page() mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" mm/gup_benchmark: support pin_user_pages() and related calls selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage mm/gup: remove support for gup(FOLL_LONGTERM)
Documentation/core-api/index.rst | 1 + Documentation/core-api/pin_user_pages.rst | 218 +++++++ arch/powerpc/mm/book3s64/iommu_api.c | 15 +- drivers/gpu/drm/via/via_dmablit.c | 2 +- drivers/infiniband/core/umem.c | 17 +- drivers/infiniband/core/umem_odp.c | 13 +- drivers/infiniband/hw/hfi1/user_pages.c | 4 +- drivers/infiniband/hw/mthca/mthca_memfree.c | 3 +- drivers/infiniband/hw/qib/qib_user_pages.c | 8 +- drivers/infiniband/hw/qib/qib_user_sdma.c | 2 +- drivers/infiniband/hw/usnic/usnic_uiom.c | 9 +- drivers/infiniband/sw/siw/siw_mem.c | 5 +- drivers/media/v4l2-core/videobuf-dma-sg.c | 10 +- drivers/platform/goldfish/goldfish_pipe.c | 35 +- drivers/vfio/vfio_iommu_type1.c | 30 +- fs/io_uring.c | 5 +- include/linux/mm.h | 164 ++++- include/linux/mmzone.h | 2 + include/linux/page_ref.h | 10 + mm/gup.c | 636 ++++++++++++++++---- mm/gup_benchmark.c | 87 ++- mm/huge_memory.c | 54 +- mm/hugetlb.c | 39 +- mm/memremap.c | 67 +-- mm/process_vm_access.c | 28 +- mm/vmstat.c | 2 + net/xdp/xdp_umem.c | 4 +- tools/testing/selftests/vm/gup_benchmark.c | 34 +- tools/testing/selftests/vm/run_vmtests | 22 + 29 files changed, 1191 insertions(+), 335 deletions(-) create mode 100644 Documentation/core-api/pin_user_pages.rst