FAILED: patch "[PATCH] mm: migration: fix migration of huge PMD shared pages" failed to apply to 4.4-stable tree
The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 017b1660df89f5fb4bfe66c34e35f7d2031100c7 Mon Sep 17 00:00:00 2001
From: Mike Kravetz mike.kravetz@oracle.com Date: Fri, 5 Oct 2018 15:51:29 -0700 Subject: [PATCH] mm: migration: fix migration of huge PMD shared pages
The page migration code employs try_to_unmap() to try and unmap the source page. This is accomplished by using rmap_walk to find all vmas where the page is mapped. This search stops when page mapcount is zero. For shared PMD huge pages, the page map count is always 1 no matter the number of mappings. Shared mappings are tracked via the reference count of the PMD page. Therefore, try_to_unmap stops prematurely and does not completely unmap all mappings of the source page.
This problem can result is data corruption as writes to the original source page can happen after contents of the page are copied to the target page. Hence, data is lost.
This problem was originally seen as DB corruption of shared global areas after a huge page was soft offlined due to ECC memory errors. DB developers noticed they could reproduce the issue by (hotplug) offlining memory used to back huge pages. A simple testcase can reproduce the problem by creating a shared PMD mapping (note that this must be at least PUD_SIZE in size and PUD_SIZE aligned (1GB on x86)), and using migrate_pages() to migrate process pages between nodes while continually writing to the huge pages being migrated.
To fix, have the try_to_unmap_one routine check for huge PMD sharing by calling huge_pmd_unshare for hugetlbfs huge pages. If it is a shared mapping it will be 'unshared' which removes the page table entry and drops the reference on the PMD page. After this, flush caches and TLB.
mmu notifiers are called before locking page tables, but we can not be sure of PMD sharing until page tables are locked. Therefore, check for the possibility of PMD sharing before locking so that notifiers can prepare for the worst possible case.
Link: http://lkml.kernel.org/r/20180823205917.16297-2-mike.kravetz@oracle.com [mike.kravetz@oracle.com: make _range_in_vma() a static inline] Link: http://lkml.kernel.org/r/6063f215-a5c8-2f0c-465a-2c515ddc952d@oracle.com Fixes: 39dde65c9940 ("shared page table for hugetlb page") Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Reviewed-by: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Acked-by: Michal Hocko mhocko@suse.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Davidlohr Bueso dave@stgolabs.net Cc: Jerome Glisse jglisse@redhat.com Cc: Mike Kravetz mike.kravetz@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 6b68e345f0ca..087fd5f48c91 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -140,6 +140,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr, unsigned long sz); int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep); +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end); struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int write); struct page *follow_huge_pd(struct vm_area_struct *vma, @@ -170,6 +172,18 @@ static inline unsigned long hugetlb_total_pages(void) return 0; }
+static inline int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, + pte_t *ptep) +{ + return 0; +} + +static inline void adjust_range_if_pmd_sharing_possible( + struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ +} + #define follow_hugetlb_page(m,v,p,vs,a,b,i,w,n) ({ BUG(); 0; }) #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL) #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; }) diff --git a/include/linux/mm.h b/include/linux/mm.h index a61ebe8ad4ca..0416a7204be3 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2455,6 +2455,12 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm, return vma; }
+static inline bool range_in_vma(struct vm_area_struct *vma, + unsigned long start, unsigned long end) +{ + return (vma && vma->vm_start <= start && end <= vma->vm_end); +} + #ifdef CONFIG_MMU pgprot_t vm_get_page_prot(unsigned long vm_flags); void vma_set_page_prot(struct vm_area_struct *vma); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 3c21775f196b..b903d746e132 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4545,12 +4545,40 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) /* * check on proper vm_flags and page table alignment */ - if (vma->vm_flags & VM_MAYSHARE && - vma->vm_start <= base && end <= vma->vm_end) + if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end)) return true; return false; }
+/* + * Determine if start,end range within vma could be mapped by shared pmd. + * If yes, adjust start and end to cover range associated with possible + * shared pmd mappings. + */ +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ + unsigned long check_addr = *start; + + if (!(vma->vm_flags & VM_MAYSHARE)) + return; + + for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) { + unsigned long a_start = check_addr & PUD_MASK; + unsigned long a_end = a_start + PUD_SIZE; + + /* + * If sharing is possible, adjust start/end if necessary. + */ + if (range_in_vma(vma, a_start, a_end)) { + if (a_start < *start) + *start = a_start; + if (a_end > *end) + *end = a_end; + } + } +} + /* * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc() * and returns the corresponding pte. While this is not necessary for the @@ -4648,6 +4676,11 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) { return 0; } + +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ +} #define want_pmd_share() (0) #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
diff --git a/mm/rmap.c b/mm/rmap.c index eb477809a5c0..1e79fac3186b 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1362,11 +1362,21 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, }
/* - * We have to assume the worse case ie pmd for invalidation. Note that - * the page can not be free in this function as call of try_to_unmap() - * must hold a reference on the page. + * For THP, we have to assume the worse case ie pmd for invalidation. + * For hugetlb, it could be much worse if we need to do pud + * invalidation in the case of pmd sharing. + * + * Note that the page can not be free in this function as call of + * try_to_unmap() must hold a reference on the page. */ end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page))); + if (PageHuge(page)) { + /* + * If sharing is possible, start and end will be adjusted + * accordingly. + */ + adjust_range_if_pmd_sharing_possible(vma, &start, &end); + } mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
while (page_vma_mapped_walk(&pvmw)) { @@ -1409,6 +1419,32 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte); address = pvmw.address;
+ if (PageHuge(page)) { + if (huge_pmd_unshare(mm, &address, pvmw.pte)) { + /* + * huge_pmd_unshare unmapped an entire PMD + * page. There is no way of knowing exactly + * which PMDs may be cached for this mm, so + * we must flush them all. start/end were + * already adjusted above to cover this range. + */ + flush_cache_range(vma, start, end); + flush_tlb_range(vma, start, end); + mmu_notifier_invalidate_range(mm, start, end); + + /* + * The ref count of the PMD page was dropped + * which is part of the way map counting + * is done for shared PMDs. Return 'true' + * here. When there is no other sharing, + * huge_pmd_unshare returns false and we will + * unmap the actual page and drop map count + * to zero. + */ + page_vma_mapped_walk_done(&pvmw); + break; + } + }
if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
On 10/10/18 11:04 PM, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
After completing the upstream patch, Michal, Jerome and myself had a discussion about how to do a backport (specifically to 4.4). I don't think we ever came to a definitive conclusion. So, there may be additional discussion needed here. But, the following is what I have.
From: Mike Kravetz mike.kravetz@oracle.com
mm: migration: fix migration of huge PMD shared pages
commit 017b1660df89f5fb4bfe66c34e35f7d2031100c7 upstream
The page migration code employs try_to_unmap() to try and unmap the source page. This is accomplished by using rmap_walk to find all vmas where the page is mapped. This search stops when page mapcount is zero. For shared PMD huge pages, the page map count is always 1 no matter the number of mappings. Shared mappings are tracked via the reference count of the PMD page. Therefore, try_to_unmap stops prematurely and does not completely unmap all mappings of the source page.
This problem can result is data corruption as writes to the original source page can happen after contents of the page are copied to the target page. Hence, data is lost.
This problem was originally seen as DB corruption of shared global areas after a huge page was soft offlined due to ECC memory errors. DB developers noticed they could reproduce the issue by (hotplug) offlining memory used to back huge pages. A simple testcase can reproduce the problem by creating a shared PMD mapping (note that this must be at least PUD_SIZE in size and PUD_SIZE aligned (1GB on x86)), and using migrate_pages() to migrate process pages between nodes while continually writing to the huge pages being migrated.
To fix, have the try_to_unmap_one routine check for huge PMD sharing by calling huge_pmd_unshare for hugetlbfs huge pages. If it is a shared mapping it will be 'unshared' which removes the page table entry and drops the reference on the PMD page. After this, flush caches and TLB.
mmu notifiers are called before locking page tables, but we can not be sure of PMD sharing until page tables are locked. Therefore, check for the possibility of PMD sharing before locking so that notifiers can prepare for the worst possible case.
Fixes: 39dde65c9940 ("shared page table for hugetlb page") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com --- include/linux/hugetlb.h | 14 +++++++++++ include/linux/mm.h | 6 +++++ mm/hugetlb.c | 37 ++++++++++++++++++++++++++-- mm/rmap.c | 54 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 109 insertions(+), 2 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 685c262e0be8..3957d99e66ea 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -110,6 +110,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz); pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr); int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep); +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end); struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int write); struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address, @@ -132,6 +134,18 @@ static inline unsigned long hugetlb_total_pages(void) return 0; }
+static inline int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, + pte_t *ptep) +{ + return 0; +} + +static inline void adjust_range_if_pmd_sharing_possible( + struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ +} + #define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; }) #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL) #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; }) diff --git a/include/linux/mm.h b/include/linux/mm.h index 1f4366567e7d..d4e8077fca96 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2058,6 +2058,12 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm, return vma; }
+static inline bool range_in_vma(struct vm_area_struct *vma, + unsigned long start, unsigned long end) +{ + return (vma && vma->vm_start <= start && end <= vma->vm_end); +} + #ifdef CONFIG_MMU pgprot_t vm_get_page_prot(unsigned long vm_flags); void vma_set_page_prot(struct vm_area_struct *vma); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a813b03021b7..279c4d87deeb 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4195,12 +4195,40 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) /* * check on proper vm_flags and page table alignment */ - if (vma->vm_flags & VM_MAYSHARE && - vma->vm_start <= base && end <= vma->vm_end) + if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end)) return true; return false; }
+/* + * Determine if start,end range within vma could be mapped by shared pmd. + * If yes, adjust start and end to cover range associated with possible + * shared pmd mappings. + */ +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ + unsigned long check_addr = *start; + + if (!(vma->vm_flags & VM_MAYSHARE)) + return; + + for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) { + unsigned long a_start = check_addr & PUD_MASK; + unsigned long a_end = a_start + PUD_SIZE; + + /* + * If sharing is possible, adjust start/end if necessary. + */ + if (range_in_vma(vma, a_start, a_end)) { + if (a_start < *start) + *start = a_start; + if (a_end > *end) + *end = a_end; + } + } +} + /* * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc() * and returns the corresponding pte. While this is not necessary for the @@ -4297,6 +4325,11 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) { return 0; } + +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ +} #define want_pmd_share() (0) #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..c9209fc69376 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,6 +1324,9 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN; + unsigned long sh_address; + bool pmd_sharing_possible = false; + unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ @@ -1334,6 +1337,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, if (!pte) goto out;
+ /* + * Only use the range_start/end mmu notifiers if huge pmd sharing + * is possible. + */ + if (PageHuge(page)) { + spmd_start = address; + spmd_end = spmd_start + vma_mmu_pagesize(vma); + + /* + * Check if pmd sharing is possible. If possible, we could + * unmap a PUD_SIZE range. spmd_start/spmd_end will be + * modified if sharing is possible. + */ + adjust_range_if_pmd_sharing_possible(vma, &spmd_start, + &spmd_end); + if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) { + sh_address = address; + + pmd_sharing_possible = true; + mmu_notifier_invalidate_range_start(vma->vm_mm, + spmd_start, spmd_end); + } + } + /* * If the page is mlock()d, we cannot swap it out. * If it's recently referenced (perhaps page_referenced @@ -1356,6 +1383,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } }
+ /* + * Call huge_pmd_unshare to potentially unshare a huge pmd. Pass + * sh_address as it will be modified if unsharing is successful. + */ + if (PageHuge(page) && huge_pmd_unshare(mm, &sh_address, pte)) { + /* + * huge_pmd_unshare unmapped an entire PMD page. There is + * no way of knowing exactly which PMDs may be cached for + * this mm, so flush them all. spmd_start/spmd_end cover + * this PUD_SIZE range. + */ + flush_cache_range(vma, spmd_start, spmd_end); + flush_tlb_range(vma, spmd_start, spmd_end); + + /* + * The ref count of the PMD page was dropped which is part + * of the way map counting is done for shared PMDs. When + * there is no other sharing, huge_pmd_unshare returns false + * and we will unmap the actual page and drop map count + * to zero. + */ + goto out_unmap; + } + /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); if (should_defer_flush(mm, flags)) { @@ -1449,6 +1500,9 @@ out_unmap: pte_unmap_unlock(pte, ptl); if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK)) mmu_notifier_invalidate_page(mm, address); + if (pmd_sharing_possible) + mmu_notifier_invalidate_range_end(vma->vm_mm, + spmd_start, spmd_end); out: return ret; }
On Thu, Oct 11, 2018 at 03:42:59PM -0700, Mike Kravetz wrote:
On 10/10/18 11:04 PM, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
After completing the upstream patch, Michal, Jerome and myself had a discussion about how to do a backport (specifically to 4.4). I don't think we ever came to a definitive conclusion. So, there may be additional discussion needed here. But, the following is what I have.
What about 4.9? It's also needed there, will this patch also work there?
thanks,
greg k-h
On 10/16/18 6:55 AM, Greg KH wrote:
On Thu, Oct 11, 2018 at 03:42:59PM -0700, Mike Kravetz wrote:
On 10/10/18 11:04 PM, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
After completing the upstream patch, Michal, Jerome and myself had a discussion about how to do a backport (specifically to 4.4). I don't think we ever came to a definitive conclusion. So, there may be additional discussion needed here. But, the following is what I have.
What about 4.9? It's also needed there, will this patch also work there?
I'll put together a version for 4.9. Was just waiting to see if Michal or Jerome had any comments on this patch/approach.
On Thu 11-10-18 15:42:59, Mike Kravetz wrote:
From: Mike Kravetz mike.kravetz@oracle.com
mm: migration: fix migration of huge PMD shared pages
commit 017b1660df89f5fb4bfe66c34e35f7d2031100c7 upstream
The page migration code employs try_to_unmap() to try and unmap the source page. This is accomplished by using rmap_walk to find all vmas where the page is mapped. This search stops when page mapcount is zero. For shared PMD huge pages, the page map count is always 1 no matter the number of mappings. Shared mappings are tracked via the reference count of the PMD page. Therefore, try_to_unmap stops prematurely and does not completely unmap all mappings of the source page.
This problem can result is data corruption as writes to the original source page can happen after contents of the page are copied to the target page. Hence, data is lost.
This problem was originally seen as DB corruption of shared global areas after a huge page was soft offlined due to ECC memory errors. DB developers noticed they could reproduce the issue by (hotplug) offlining memory used to back huge pages. A simple testcase can reproduce the problem by creating a shared PMD mapping (note that this must be at least PUD_SIZE in size and PUD_SIZE aligned (1GB on x86)), and using migrate_pages() to migrate process pages between nodes while continually writing to the huge pages being migrated.
To fix, have the try_to_unmap_one routine check for huge PMD sharing by calling huge_pmd_unshare for hugetlbfs huge pages. If it is a shared mapping it will be 'unshared' which removes the page table entry and drops the reference on the PMD page. After this, flush caches and TLB.
mmu notifiers are called before locking page tables, but we can not be sure of PMD sharing until page tables are locked. Therefore, check for the possibility of PMD sharing before locking so that notifiers can prepare for the worst possible case.
Fixes: 39dde65c9940 ("shared page table for hugetlb page") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com
Acked-by: Michal Hocko mhocko@suse.com
with one minor nit. Please document why we are using the range invalidation (_start/_stop) only for hugetlb pages. Because this is a divergence from the upstream and we should better be explicit about that.
I've been testing without that in place and the memory corruption hasn't reproduced so far. I cannot give 100% confidence, though, due to some unrelated road blocks when testing. I might be lucky to not really have any notifier consumer for my workload as well.
Seeing an Acked-by from Jerome on this would be reassuring of course.
On Thu, Oct 11, 2018 at 03:42:59PM -0700, Mike Kravetz wrote:
On 10/10/18 11:04 PM, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
After completing the upstream patch, Michal, Jerome and myself had a discussion about how to do a backport (specifically to 4.4). I don't think we ever came to a definitive conclusion. So, there may be additional discussion needed here. But, the following is what I have.
From: Mike Kravetz mike.kravetz@oracle.com
mm: migration: fix migration of huge PMD shared pages
commit 017b1660df89f5fb4bfe66c34e35f7d2031100c7 upstream
The page migration code employs try_to_unmap() to try and unmap the source page. This is accomplished by using rmap_walk to find all vmas where the page is mapped. This search stops when page mapcount is zero. For shared PMD huge pages, the page map count is always 1 no matter the number of mappings. Shared mappings are tracked via the reference count of the PMD page. Therefore, try_to_unmap stops prematurely and does not completely unmap all mappings of the source page.
This problem can result is data corruption as writes to the original source page can happen after contents of the page are copied to the target page. Hence, data is lost.
This problem was originally seen as DB corruption of shared global areas after a huge page was soft offlined due to ECC memory errors. DB developers noticed they could reproduce the issue by (hotplug) offlining memory used to back huge pages. A simple testcase can reproduce the problem by creating a shared PMD mapping (note that this must be at least PUD_SIZE in size and PUD_SIZE aligned (1GB on x86)), and using migrate_pages() to migrate process pages between nodes while continually writing to the huge pages being migrated.
To fix, have the try_to_unmap_one routine check for huge PMD sharing by calling huge_pmd_unshare for hugetlbfs huge pages. If it is a shared mapping it will be 'unshared' which removes the page table entry and drops the reference on the PMD page. After this, flush caches and TLB.
mmu notifiers are called before locking page tables, but we can not be sure of PMD sharing until page tables are locked. Therefore, check for the possibility of PMD sharing before locking so that notifiers can prepare for the worst possible case.
Fixes: 39dde65c9940 ("shared page table for hugetlb page") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com
include/linux/hugetlb.h | 14 +++++++++++ include/linux/mm.h | 6 +++++ mm/hugetlb.c | 37 ++++++++++++++++++++++++++-- mm/rmap.c | 54 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 109 insertions(+), 2 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 685c262e0be8..3957d99e66ea 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -110,6 +110,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz); pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr); int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep); +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end);struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int write); struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address, @@ -132,6 +134,18 @@ static inline unsigned long hugetlb_total_pages(void) return 0; } +static inline int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr,
pte_t *ptep)+{
- return 0;
+}
+static inline void adjust_range_if_pmd_sharing_possible(
struct vm_area_struct *vma,unsigned long *start, unsigned long *end)+{ +}
#define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; }) #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL) #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; }) diff --git a/include/linux/mm.h b/include/linux/mm.h index 1f4366567e7d..d4e8077fca96 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2058,6 +2058,12 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm, return vma; } +static inline bool range_in_vma(struct vm_area_struct *vma,
unsigned long start, unsigned long end)+{
- return (vma && vma->vm_start <= start && end <= vma->vm_end);
+}
#ifdef CONFIG_MMU pgprot_t vm_get_page_prot(unsigned long vm_flags); void vma_set_page_prot(struct vm_area_struct *vma); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a813b03021b7..279c4d87deeb 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4195,12 +4195,40 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) /* * check on proper vm_flags and page table alignment */
- if (vma->vm_flags & VM_MAYSHARE &&
vma->vm_start <= base && end <= vma->vm_end)
- if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end)) return true; return false;
} +/*
- Determine if start,end range within vma could be mapped by shared pmd.
- If yes, adjust start and end to cover range associated with possible
- shared pmd mappings.
- */
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)+{
- unsigned long check_addr = *start;
- if (!(vma->vm_flags & VM_MAYSHARE))
return;- for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
unsigned long a_start = check_addr & PUD_MASK;unsigned long a_end = a_start + PUD_SIZE;/** If sharing is possible, adjust start/end if necessary.*/if (range_in_vma(vma, a_start, a_end)) {if (a_start < *start)*start = a_start;if (a_end > *end)*end = a_end;}- }
+}
/*
- Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
- and returns the corresponding pte. While this is not necessary for the
@@ -4297,6 +4325,11 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) { return 0; }
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)+{ +} #define want_pmd_share() (0) #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..c9209fc69376 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,6 +1324,9 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN;
- unsigned long sh_address;
- bool pmd_sharing_possible = false;
- unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ @@ -1334,6 +1337,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, if (!pte) goto out;
- /*
* Only use the range_start/end mmu notifiers if huge pmd sharing* is possible.*/- if (PageHuge(page)) {
spmd_start = address;spmd_end = spmd_start + vma_mmu_pagesize(vma);/** Check if pmd sharing is possible. If possible, we could* unmap a PUD_SIZE range. spmd_start/spmd_end will be* modified if sharing is possible.*/adjust_range_if_pmd_sharing_possible(vma, &spmd_start,&spmd_end);if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) {sh_address = address;pmd_sharing_possible = true;mmu_notifier_invalidate_range_start(vma->vm_mm,spmd_start, spmd_end);}- }
This needs to happen before page_check_address() as page_check_address() take the page table spinlock and mmu_notifier_invalidate_range_start() can sleep.
Looking at adjust_range_if_pmd_sharing_possible() and vma_mmu_pagesize() it seems they can happen before taking the page table lock.
That being said this is 4.4 i think only ODP code for infiniband would have issues with that.
[Sorry for late reply i am back from PTO and still catching up on emails]
- /*
- If the page is mlock()d, we cannot swap it out.
- If it's recently referenced (perhaps page_referenced
@@ -1356,6 +1383,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } }
- /*
* Call huge_pmd_unshare to potentially unshare a huge pmd. Pass* sh_address as it will be modified if unsharing is successful.*/- if (PageHuge(page) && huge_pmd_unshare(mm, &sh_address, pte)) {
/** huge_pmd_unshare unmapped an entire PMD page. There is* no way of knowing exactly which PMDs may be cached for* this mm, so flush them all. spmd_start/spmd_end cover* this PUD_SIZE range.*/flush_cache_range(vma, spmd_start, spmd_end);flush_tlb_range(vma, spmd_start, spmd_end);/** The ref count of the PMD page was dropped which is part* of the way map counting is done for shared PMDs. When* there is no other sharing, huge_pmd_unshare returns false* and we will unmap the actual page and drop map count* to zero.*/goto out_unmap;- }
- /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); if (should_defer_flush(mm, flags)) {
@@ -1449,6 +1500,9 @@ out_unmap: pte_unmap_unlock(pte, ptl); if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK)) mmu_notifier_invalidate_page(mm, address);
- if (pmd_sharing_possible)
mmu_notifier_invalidate_range_end(vma->vm_mm,spmd_start, spmd_end);out: return ret; } -- 2.17.1
On 10/17/18 7:30 AM, Jerome Glisse wrote:
On Thu, Oct 11, 2018 at 03:42:59PM -0700, Mike Kravetz wrote:
On 10/10/18 11:04 PM, gregkh@linuxfoundation.org wrote: diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..c9209fc69376 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,6 +1324,9 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN;
- unsigned long sh_address;
- bool pmd_sharing_possible = false;
- unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ @@ -1334,6 +1337,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, if (!pte) goto out;
- /*
* Only use the range_start/end mmu notifiers if huge pmd sharing* is possible.*/- if (PageHuge(page)) {
spmd_start = address;spmd_end = spmd_start + vma_mmu_pagesize(vma);/** Check if pmd sharing is possible. If possible, we could* unmap a PUD_SIZE range. spmd_start/spmd_end will be* modified if sharing is possible.*/adjust_range_if_pmd_sharing_possible(vma, &spmd_start,&spmd_end);if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) {sh_address = address;pmd_sharing_possible = true;mmu_notifier_invalidate_range_start(vma->vm_mm,spmd_start, spmd_end);}- }
This needs to happen before page_check_address() as page_check_address() take the page table spinlock and mmu_notifier_invalidate_range_start() can sleep.
Looking at adjust_range_if_pmd_sharing_possible() and vma_mmu_pagesize() it seems they can happen before taking the page table lock.
That being said this is 4.4 i think only ODP code for infiniband would have issues with that.
[Sorry for late reply i am back from PTO and still catching up on emails]
Thanks!
You are correct. That 'if (PageHuge(page))' should happen earlier in the routine. The adjust_range_if_pmd_sharing_possible and vma_mmu_pagesize calls are just fine there as well. In fact, that is how I have the code structured in an older kernel run internally. Not sure why I changed it in this version.
Here is an updated version with this change as well as better comments as suggested by Michal.
From: Mike Kravetz mike.kravetz@oracle.com
mm: migration: fix migration of huge PMD shared pages
commit 017b1660df89f5fb4bfe66c34e35f7d2031100c7 upstream
The page migration code employs try_to_unmap() to try and unmap the source page. This is accomplished by using rmap_walk to find all vmas where the page is mapped. This search stops when page mapcount is zero. For shared PMD huge pages, the page map count is always 1 no matter the number of mappings. Shared mappings are tracked via the reference count of the PMD page. Therefore, try_to_unmap stops prematurely and does not completely unmap all mappings of the source page.
This problem can result is data corruption as writes to the original source page can happen after contents of the page are copied to the target page. Hence, data is lost.
This problem was originally seen as DB corruption of shared global areas after a huge page was soft offlined due to ECC memory errors. DB developers noticed they could reproduce the issue by (hotplug) offlining memory used to back huge pages. A simple testcase can reproduce the problem by creating a shared PMD mapping (note that this must be at least PUD_SIZE in size and PUD_SIZE aligned (1GB on x86)), and using migrate_pages() to migrate process pages between nodes while continually writing to the huge pages being migrated.
To fix, have the try_to_unmap_one routine check for huge PMD sharing by calling huge_pmd_unshare for hugetlbfs huge pages. If it is a shared mapping it will be 'unshared' which removes the page table entry and drops the reference on the PMD page. After this, flush caches and TLB.
mmu notifiers are called before locking page tables, but we can not be sure of PMD sharing until page tables are locked. Therefore, check for the possibility of PMD sharing before locking so that notifiers can prepare for the worst possible case. The mmu notifier calls in this commit are different than upstream. That is because upstream went to a different model here. Instead of moving to the new model, we leave existing model unchanged and only use the mmu_*range* calles in this special case.
Fixes: 39dde65c9940 ("shared page table for hugetlb page") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com --- include/linux/hugetlb.h | 14 +++++++++++ include/linux/mm.h | 6 +++++ mm/hugetlb.c | 37 +++++++++++++++++++++++++-- mm/rmap.c | 56 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 111 insertions(+), 2 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 685c262e0be8..3957d99e66ea 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -110,6 +110,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz); pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr); int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep); +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end); struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int write); struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address, @@ -132,6 +134,18 @@ static inline unsigned long hugetlb_total_pages(void) return 0; }
+static inline int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, + pte_t *ptep) +{ + return 0; +} + +static inline void adjust_range_if_pmd_sharing_possible( + struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ +} + #define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; }) #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL) #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; }) diff --git a/include/linux/mm.h b/include/linux/mm.h index 1f4366567e7d..d4e8077fca96 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2058,6 +2058,12 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm, return vma; }
+static inline bool range_in_vma(struct vm_area_struct *vma, + unsigned long start, unsigned long end) +{ + return (vma && vma->vm_start <= start && end <= vma->vm_end); +} + #ifdef CONFIG_MMU pgprot_t vm_get_page_prot(unsigned long vm_flags); void vma_set_page_prot(struct vm_area_struct *vma); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a813b03021b7..279c4d87deeb 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4195,12 +4195,40 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) /* * check on proper vm_flags and page table alignment */ - if (vma->vm_flags & VM_MAYSHARE && - vma->vm_start <= base && end <= vma->vm_end) + if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end)) return true; return false; }
+/* + * Determine if start,end range within vma could be mapped by shared pmd. + * If yes, adjust start and end to cover range associated with possible + * shared pmd mappings. + */ +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ + unsigned long check_addr = *start; + + if (!(vma->vm_flags & VM_MAYSHARE)) + return; + + for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) { + unsigned long a_start = check_addr & PUD_MASK; + unsigned long a_end = a_start + PUD_SIZE; + + /* + * If sharing is possible, adjust start/end if necessary. + */ + if (range_in_vma(vma, a_start, a_end)) { + if (a_start < *start) + *start = a_start; + if (a_end > *end) + *end = a_end; + } + } +} + /* * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc() * and returns the corresponding pte. While this is not necessary for the @@ -4297,6 +4325,11 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) { return 0; } + +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ +} #define want_pmd_share() (0) #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..488dda209431 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,12 +1324,41 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN; + unsigned long sh_address; + bool pmd_sharing_possible = false; + unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) goto out;
+ /* + * Only use the range_start/end mmu notifiers if huge pmd sharing + * is possible. In the normal case, mmu_notifier_invalidate_page + * is sufficient as we only unmap a page. However, if we unshare + * a pmd, we will unmap a PUD_SIZE range. + */ + if (PageHuge(page)) { + spmd_start = address; + spmd_end = spmd_start + vma_mmu_pagesize(vma); + + /* + * Check if pmd sharing is possible. If possible, we could + * unmap a PUD_SIZE range. spmd_start/spmd_end will be + * modified if sharing is possible. + */ + adjust_range_if_pmd_sharing_possible(vma, &spmd_start, + &spmd_end); + if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) { + sh_address = address; + + pmd_sharing_possible = true; + mmu_notifier_invalidate_range_start(vma->vm_mm, + spmd_start, spmd_end); + } + } + pte = page_check_address(page, mm, address, &ptl, 0); if (!pte) goto out; @@ -1356,6 +1385,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } }
+ /* + * Call huge_pmd_unshare to potentially unshare a huge pmd. Pass + * sh_address as it will be modified if unsharing is successful. + */ + if (PageHuge(page) && huge_pmd_unshare(mm, &sh_address, pte)) { + /* + * huge_pmd_unshare unmapped an entire PMD page. There is + * no way of knowing exactly which PMDs may be cached for + * this mm, so flush them all. spmd_start/spmd_end cover + * this PUD_SIZE range. + */ + flush_cache_range(vma, spmd_start, spmd_end); + flush_tlb_range(vma, spmd_start, spmd_end); + + /* + * The ref count of the PMD page was dropped which is part + * of the way map counting is done for shared PMDs. When + * there is no other sharing, huge_pmd_unshare returns false + * and we will unmap the actual page and drop map count + * to zero. + */ + goto out_unmap; + } + /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); if (should_defer_flush(mm, flags)) { @@ -1450,6 +1503,9 @@ out_unmap: if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK)) mmu_notifier_invalidate_page(mm, address); out: + if (pmd_sharing_possible) + mmu_notifier_invalidate_range_end(vma->vm_mm, + spmd_start, spmd_end); return ret; }
On Wed, Oct 17, 2018 at 08:23:34AM -0700, Mike Kravetz wrote:
On 10/17/18 7:30 AM, Jerome Glisse wrote:
On Thu, Oct 11, 2018 at 03:42:59PM -0700, Mike Kravetz wrote:
On 10/10/18 11:04 PM, gregkh@linuxfoundation.org wrote: diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..c9209fc69376 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,6 +1324,9 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN;
- unsigned long sh_address;
- bool pmd_sharing_possible = false;
- unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ @@ -1334,6 +1337,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, if (!pte) goto out;
- /*
* Only use the range_start/end mmu notifiers if huge pmd sharing* is possible.*/- if (PageHuge(page)) {
spmd_start = address;spmd_end = spmd_start + vma_mmu_pagesize(vma);/** Check if pmd sharing is possible. If possible, we could* unmap a PUD_SIZE range. spmd_start/spmd_end will be* modified if sharing is possible.*/adjust_range_if_pmd_sharing_possible(vma, &spmd_start,&spmd_end);if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) {sh_address = address;pmd_sharing_possible = true;mmu_notifier_invalidate_range_start(vma->vm_mm,spmd_start, spmd_end);}- }
This needs to happen before page_check_address() as page_check_address() take the page table spinlock and mmu_notifier_invalidate_range_start() can sleep.
Looking at adjust_range_if_pmd_sharing_possible() and vma_mmu_pagesize() it seems they can happen before taking the page table lock.
That being said this is 4.4 i think only ODP code for infiniband would have issues with that.
[Sorry for late reply i am back from PTO and still catching up on emails]
Thanks!
You are correct. That 'if (PageHuge(page))' should happen earlier in the routine. The adjust_range_if_pmd_sharing_possible and vma_mmu_pagesize calls are just fine there as well. In fact, that is how I have the code structured in an older kernel run internally. Not sure why I changed it in this version.
Here is an updated version with this change as well as better comments as suggested by Michal.
From: Mike Kravetz mike.kravetz@oracle.com
mm: migration: fix migration of huge PMD shared pages
commit 017b1660df89f5fb4bfe66c34e35f7d2031100c7 upstream
The page migration code employs try_to_unmap() to try and unmap the source page. This is accomplished by using rmap_walk to find all vmas where the page is mapped. This search stops when page mapcount is zero. For shared PMD huge pages, the page map count is always 1 no matter the number of mappings. Shared mappings are tracked via the reference count of the PMD page. Therefore, try_to_unmap stops prematurely and does not completely unmap all mappings of the source page.
This problem can result is data corruption as writes to the original source page can happen after contents of the page are copied to the target page. Hence, data is lost.
This problem was originally seen as DB corruption of shared global areas after a huge page was soft offlined due to ECC memory errors. DB developers noticed they could reproduce the issue by (hotplug) offlining memory used to back huge pages. A simple testcase can reproduce the problem by creating a shared PMD mapping (note that this must be at least PUD_SIZE in size and PUD_SIZE aligned (1GB on x86)), and using migrate_pages() to migrate process pages between nodes while continually writing to the huge pages being migrated.
To fix, have the try_to_unmap_one routine check for huge PMD sharing by calling huge_pmd_unshare for hugetlbfs huge pages. If it is a shared mapping it will be 'unshared' which removes the page table entry and drops the reference on the PMD page. After this, flush caches and TLB.
mmu notifiers are called before locking page tables, but we can not be sure of PMD sharing until page tables are locked. Therefore, check for the possibility of PMD sharing before locking so that notifiers can prepare for the worst possible case. The mmu notifier calls in this commit are different than upstream. That is because upstream went to a different model here. Instead of moving to the new model, we leave existing model unchanged and only use the mmu_*range* calles in this special case.
Fixes: 39dde65c9940 ("shared page table for hugetlb page") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com
Reviewed-by: Jérôme Glisse jglisse@redhat.com
include/linux/hugetlb.h | 14 +++++++++++ include/linux/mm.h | 6 +++++ mm/hugetlb.c | 37 +++++++++++++++++++++++++-- mm/rmap.c | 56 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 111 insertions(+), 2 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 685c262e0be8..3957d99e66ea 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -110,6 +110,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz); pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr); int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep); +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end);struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int write); struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address, @@ -132,6 +134,18 @@ static inline unsigned long hugetlb_total_pages(void) return 0; } +static inline int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr,
pte_t *ptep)+{
- return 0;
+}
+static inline void adjust_range_if_pmd_sharing_possible(
struct vm_area_struct *vma,unsigned long *start, unsigned long *end)+{ +}
#define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; }) #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL) #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; }) diff --git a/include/linux/mm.h b/include/linux/mm.h index 1f4366567e7d..d4e8077fca96 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2058,6 +2058,12 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm, return vma; } +static inline bool range_in_vma(struct vm_area_struct *vma,
unsigned long start, unsigned long end)+{
- return (vma && vma->vm_start <= start && end <= vma->vm_end);
+}
#ifdef CONFIG_MMU pgprot_t vm_get_page_prot(unsigned long vm_flags); void vma_set_page_prot(struct vm_area_struct *vma); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a813b03021b7..279c4d87deeb 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4195,12 +4195,40 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) /* * check on proper vm_flags and page table alignment */
- if (vma->vm_flags & VM_MAYSHARE &&
vma->vm_start <= base && end <= vma->vm_end)
- if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end)) return true; return false;
} +/*
- Determine if start,end range within vma could be mapped by shared pmd.
- If yes, adjust start and end to cover range associated with possible
- shared pmd mappings.
- */
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)+{
- unsigned long check_addr = *start;
- if (!(vma->vm_flags & VM_MAYSHARE))
return;- for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
unsigned long a_start = check_addr & PUD_MASK;unsigned long a_end = a_start + PUD_SIZE;/** If sharing is possible, adjust start/end if necessary.*/if (range_in_vma(vma, a_start, a_end)) {if (a_start < *start)*start = a_start;if (a_end > *end)*end = a_end;}- }
+}
/*
- Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
- and returns the corresponding pte. While this is not necessary for the
@@ -4297,6 +4325,11 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) { return 0; }
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)+{ +} #define want_pmd_share() (0) #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..488dda209431 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,12 +1324,41 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN;
- unsigned long sh_address;
- bool pmd_sharing_possible = false;
- unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) goto out;
- /*
* Only use the range_start/end mmu notifiers if huge pmd sharing* is possible. In the normal case, mmu_notifier_invalidate_page* is sufficient as we only unmap a page. However, if we unshare* a pmd, we will unmap a PUD_SIZE range.*/- if (PageHuge(page)) {
spmd_start = address;spmd_end = spmd_start + vma_mmu_pagesize(vma);/** Check if pmd sharing is possible. If possible, we could* unmap a PUD_SIZE range. spmd_start/spmd_end will be* modified if sharing is possible.*/adjust_range_if_pmd_sharing_possible(vma, &spmd_start,&spmd_end);if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) {sh_address = address;pmd_sharing_possible = true;mmu_notifier_invalidate_range_start(vma->vm_mm,spmd_start, spmd_end);}- }
- pte = page_check_address(page, mm, address, &ptl, 0); if (!pte) goto out;
@@ -1356,6 +1385,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } }
- /*
* Call huge_pmd_unshare to potentially unshare a huge pmd. Pass* sh_address as it will be modified if unsharing is successful.*/- if (PageHuge(page) && huge_pmd_unshare(mm, &sh_address, pte)) {
/** huge_pmd_unshare unmapped an entire PMD page. There is* no way of knowing exactly which PMDs may be cached for* this mm, so flush them all. spmd_start/spmd_end cover* this PUD_SIZE range.*/flush_cache_range(vma, spmd_start, spmd_end);flush_tlb_range(vma, spmd_start, spmd_end);/** The ref count of the PMD page was dropped which is part* of the way map counting is done for shared PMDs. When* there is no other sharing, huge_pmd_unshare returns false* and we will unmap the actual page and drop map count* to zero.*/goto out_unmap;- }
- /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); if (should_defer_flush(mm, flags)) {
@@ -1450,6 +1503,9 @@ out_unmap: if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK)) mmu_notifier_invalidate_page(mm, address); out:
- if (pmd_sharing_possible)
mmu_notifier_invalidate_range_end(vma->vm_mm,spmd_start, spmd_end);} -- 2.17.2
On 10/17/18 8:45 AM, Jerome Glisse wrote:
On Wed, Oct 17, 2018 at 08:23:34AM -0700, Mike Kravetz wrote:
On 10/17/18 7:30 AM, Jerome Glisse wrote:
On Thu, Oct 11, 2018 at 03:42:59PM -0700, Mike Kravetz wrote:
On 10/10/18 11:04 PM, gregkh@linuxfoundation.org wrote:
Reviewed-by: Jérôme Glisse jglisse@redhat.com
Thanks Jérôme.
Greg, does that latest patch work for you? If so, I will use that as a basis for v4.9 stable.
On Wed 17-10-18 08:23:34, Mike Kravetz wrote: [...]
From: Mike Kravetz mike.kravetz@oracle.com
mm: migration: fix migration of huge PMD shared pages
commit 017b1660df89f5fb4bfe66c34e35f7d2031100c7 upstream
The page migration code employs try_to_unmap() to try and unmap the source page. This is accomplished by using rmap_walk to find all vmas where the page is mapped. This search stops when page mapcount is zero. For shared PMD huge pages, the page map count is always 1 no matter the number of mappings. Shared mappings are tracked via the reference count of the PMD page. Therefore, try_to_unmap stops prematurely and does not completely unmap all mappings of the source page.
This problem can result is data corruption as writes to the original source page can happen after contents of the page are copied to the target page. Hence, data is lost.
This problem was originally seen as DB corruption of shared global areas after a huge page was soft offlined due to ECC memory errors. DB developers noticed they could reproduce the issue by (hotplug) offlining memory used to back huge pages. A simple testcase can reproduce the problem by creating a shared PMD mapping (note that this must be at least PUD_SIZE in size and PUD_SIZE aligned (1GB on x86)), and using migrate_pages() to migrate process pages between nodes while continually writing to the huge pages being migrated.
To fix, have the try_to_unmap_one routine check for huge PMD sharing by calling huge_pmd_unshare for hugetlbfs huge pages. If it is a shared mapping it will be 'unshared' which removes the page table entry and drops the reference on the PMD page. After this, flush caches and TLB.
mmu notifiers are called before locking page tables, but we can not be sure of PMD sharing until page tables are locked. Therefore, check for the possibility of PMD sharing before locking so that notifiers can prepare for the worst possible case. The mmu notifier calls in this commit are different than upstream. That is because upstream went to a different model here. Instead of moving to the new model, we leave existing model unchanged and only use the mmu_*range* calles in this special case.
Fixes: 39dde65c9940 ("shared page table for hugetlb page") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com
Thanks for the update and sorry I've missed the issue with the pte lock previously.
Acked-by: Michal Hocko mhocko@suse.com
include/linux/hugetlb.h | 14 +++++++++++ include/linux/mm.h | 6 +++++ mm/hugetlb.c | 37 +++++++++++++++++++++++++-- mm/rmap.c | 56 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 111 insertions(+), 2 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 685c262e0be8..3957d99e66ea 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -110,6 +110,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz); pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr); int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep); +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end);struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int write); struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address, @@ -132,6 +134,18 @@ static inline unsigned long hugetlb_total_pages(void) return 0; } +static inline int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr,
pte_t *ptep)+{
- return 0;
+}
+static inline void adjust_range_if_pmd_sharing_possible(
struct vm_area_struct *vma,unsigned long *start, unsigned long *end)+{ +}
#define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; }) #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL) #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; }) diff --git a/include/linux/mm.h b/include/linux/mm.h index 1f4366567e7d..d4e8077fca96 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2058,6 +2058,12 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm, return vma; } +static inline bool range_in_vma(struct vm_area_struct *vma,
unsigned long start, unsigned long end)+{
- return (vma && vma->vm_start <= start && end <= vma->vm_end);
+}
#ifdef CONFIG_MMU pgprot_t vm_get_page_prot(unsigned long vm_flags); void vma_set_page_prot(struct vm_area_struct *vma); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a813b03021b7..279c4d87deeb 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4195,12 +4195,40 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) /* * check on proper vm_flags and page table alignment */
- if (vma->vm_flags & VM_MAYSHARE &&
vma->vm_start <= base && end <= vma->vm_end)
- if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end)) return true; return false;
} +/*
- Determine if start,end range within vma could be mapped by shared pmd.
- If yes, adjust start and end to cover range associated with possible
- shared pmd mappings.
- */
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)+{
- unsigned long check_addr = *start;
- if (!(vma->vm_flags & VM_MAYSHARE))
return;- for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
unsigned long a_start = check_addr & PUD_MASK;unsigned long a_end = a_start + PUD_SIZE;/** If sharing is possible, adjust start/end if necessary.*/if (range_in_vma(vma, a_start, a_end)) {if (a_start < *start)*start = a_start;if (a_end > *end)*end = a_end;}- }
+}
/*
- Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
- and returns the corresponding pte. While this is not necessary for the
@@ -4297,6 +4325,11 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) { return 0; }
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)+{ +} #define want_pmd_share() (0) #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..488dda209431 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,12 +1324,41 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN;
- unsigned long sh_address;
- bool pmd_sharing_possible = false;
- unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) goto out;
- /*
* Only use the range_start/end mmu notifiers if huge pmd sharing* is possible. In the normal case, mmu_notifier_invalidate_page* is sufficient as we only unmap a page. However, if we unshare* a pmd, we will unmap a PUD_SIZE range.*/- if (PageHuge(page)) {
spmd_start = address;spmd_end = spmd_start + vma_mmu_pagesize(vma);/** Check if pmd sharing is possible. If possible, we could* unmap a PUD_SIZE range. spmd_start/spmd_end will be* modified if sharing is possible.*/adjust_range_if_pmd_sharing_possible(vma, &spmd_start,&spmd_end);if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) {sh_address = address;pmd_sharing_possible = true;mmu_notifier_invalidate_range_start(vma->vm_mm,spmd_start, spmd_end);}- }
- pte = page_check_address(page, mm, address, &ptl, 0); if (!pte) goto out;
@@ -1356,6 +1385,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } }
- /*
* Call huge_pmd_unshare to potentially unshare a huge pmd. Pass* sh_address as it will be modified if unsharing is successful.*/- if (PageHuge(page) && huge_pmd_unshare(mm, &sh_address, pte)) {
/** huge_pmd_unshare unmapped an entire PMD page. There is* no way of knowing exactly which PMDs may be cached for* this mm, so flush them all. spmd_start/spmd_end cover* this PUD_SIZE range.*/flush_cache_range(vma, spmd_start, spmd_end);flush_tlb_range(vma, spmd_start, spmd_end);/** The ref count of the PMD page was dropped which is part* of the way map counting is done for shared PMDs. When* there is no other sharing, huge_pmd_unshare returns false* and we will unmap the actual page and drop map count* to zero.*/goto out_unmap;- }
- /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); if (should_defer_flush(mm, flags)) {
@@ -1450,6 +1503,9 @@ out_unmap: if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK)) mmu_notifier_invalidate_page(mm, address); out:
- if (pmd_sharing_possible)
mmu_notifier_invalidate_range_end(vma->vm_mm,spmd_start, spmd_end);} -- 2.17.2
On Wed, Oct 17, 2018 at 08:23:34AM -0700, Mike Kravetz wrote:
On 10/17/18 7:30 AM, Jerome Glisse wrote:
On Thu, Oct 11, 2018 at 03:42:59PM -0700, Mike Kravetz wrote:
On 10/10/18 11:04 PM, gregkh@linuxfoundation.org wrote: diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..c9209fc69376 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,6 +1324,9 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN;
- unsigned long sh_address;
- bool pmd_sharing_possible = false;
- unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ @@ -1334,6 +1337,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, if (!pte) goto out;
- /*
* Only use the range_start/end mmu notifiers if huge pmd sharing* is possible.*/- if (PageHuge(page)) {
spmd_start = address;spmd_end = spmd_start + vma_mmu_pagesize(vma);/** Check if pmd sharing is possible. If possible, we could* unmap a PUD_SIZE range. spmd_start/spmd_end will be* modified if sharing is possible.*/adjust_range_if_pmd_sharing_possible(vma, &spmd_start,&spmd_end);if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) {sh_address = address;pmd_sharing_possible = true;mmu_notifier_invalidate_range_start(vma->vm_mm,spmd_start, spmd_end);}- }
This needs to happen before page_check_address() as page_check_address() take the page table spinlock and mmu_notifier_invalidate_range_start() can sleep.
Looking at adjust_range_if_pmd_sharing_possible() and vma_mmu_pagesize() it seems they can happen before taking the page table lock.
That being said this is 4.4 i think only ODP code for infiniband would have issues with that.
[Sorry for late reply i am back from PTO and still catching up on emails]
Thanks!
You are correct. That 'if (PageHuge(page))' should happen earlier in the routine. The adjust_range_if_pmd_sharing_possible and vma_mmu_pagesize calls are just fine there as well. In fact, that is how I have the code structured in an older kernel run internally. Not sure why I changed it in this version.
Here is an updated version with this change as well as better comments as suggested by Michal.
From: Mike Kravetz mike.kravetz@oracle.com
mm: migration: fix migration of huge PMD shared pages
commit 017b1660df89f5fb4bfe66c34e35f7d2031100c7 upstream
The page migration code employs try_to_unmap() to try and unmap the source page. This is accomplished by using rmap_walk to find all vmas where the page is mapped. This search stops when page mapcount is zero. For shared PMD huge pages, the page map count is always 1 no matter the number of mappings. Shared mappings are tracked via the reference count of the PMD page. Therefore, try_to_unmap stops prematurely and does not completely unmap all mappings of the source page.
This problem can result is data corruption as writes to the original source page can happen after contents of the page are copied to the target page. Hence, data is lost.
This problem was originally seen as DB corruption of shared global areas after a huge page was soft offlined due to ECC memory errors. DB developers noticed they could reproduce the issue by (hotplug) offlining memory used to back huge pages. A simple testcase can reproduce the problem by creating a shared PMD mapping (note that this must be at least PUD_SIZE in size and PUD_SIZE aligned (1GB on x86)), and using migrate_pages() to migrate process pages between nodes while continually writing to the huge pages being migrated.
To fix, have the try_to_unmap_one routine check for huge PMD sharing by calling huge_pmd_unshare for hugetlbfs huge pages. If it is a shared mapping it will be 'unshared' which removes the page table entry and drops the reference on the PMD page. After this, flush caches and TLB.
mmu notifiers are called before locking page tables, but we can not be sure of PMD sharing until page tables are locked. Therefore, check for the possibility of PMD sharing before locking so that notifiers can prepare for the worst possible case. The mmu notifier calls in this commit are different than upstream. That is because upstream went to a different model here. Instead of moving to the new model, we leave existing model unchanged and only use the mmu_*range* calles in this special case.
Fixes: 39dde65c9940 ("shared page table for hugetlb page") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com
include/linux/hugetlb.h | 14 +++++++++++ include/linux/mm.h | 6 +++++ mm/hugetlb.c | 37 +++++++++++++++++++++++++-- mm/rmap.c | 56 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 111 insertions(+), 2 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 685c262e0be8..3957d99e66ea 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -110,6 +110,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz); pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr); int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep); +void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end);struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int write); struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address, @@ -132,6 +134,18 @@ static inline unsigned long hugetlb_total_pages(void) return 0; } +static inline int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr,
pte_t *ptep)+{
- return 0;
+}
+static inline void adjust_range_if_pmd_sharing_possible(
struct vm_area_struct *vma,unsigned long *start, unsigned long *end)+{ +}
#define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; }) #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL) #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; }) diff --git a/include/linux/mm.h b/include/linux/mm.h index 1f4366567e7d..d4e8077fca96 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2058,6 +2058,12 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm, return vma; } +static inline bool range_in_vma(struct vm_area_struct *vma,
unsigned long start, unsigned long end)+{
- return (vma && vma->vm_start <= start && end <= vma->vm_end);
+}
#ifdef CONFIG_MMU pgprot_t vm_get_page_prot(unsigned long vm_flags); void vma_set_page_prot(struct vm_area_struct *vma); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a813b03021b7..279c4d87deeb 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4195,12 +4195,40 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) /* * check on proper vm_flags and page table alignment */
- if (vma->vm_flags & VM_MAYSHARE &&
vma->vm_start <= base && end <= vma->vm_end)
- if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end)) return true; return false;
} +/*
- Determine if start,end range within vma could be mapped by shared pmd.
- If yes, adjust start and end to cover range associated with possible
- shared pmd mappings.
- */
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)+{
- unsigned long check_addr = *start;
- if (!(vma->vm_flags & VM_MAYSHARE))
return;- for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
unsigned long a_start = check_addr & PUD_MASK;unsigned long a_end = a_start + PUD_SIZE;/** If sharing is possible, adjust start/end if necessary.*/if (range_in_vma(vma, a_start, a_end)) {if (a_start < *start)*start = a_start;if (a_end > *end)*end = a_end;}- }
+}
/*
- Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
- and returns the corresponding pte. While this is not necessary for the
@@ -4297,6 +4325,11 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) { return 0; }
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)+{ +} #define want_pmd_share() (0) #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ diff --git a/mm/rmap.c b/mm/rmap.c index 1bceb49aa214..488dda209431 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1324,12 +1324,41 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; spinlock_t *ptl; int ret = SWAP_AGAIN;
- unsigned long sh_address;
- bool pmd_sharing_possible = false;
- unsigned long spmd_start, spmd_end; enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */ if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) goto out;
- /*
* Only use the range_start/end mmu notifiers if huge pmd sharing* is possible. In the normal case, mmu_notifier_invalidate_page* is sufficient as we only unmap a page. However, if we unshare* a pmd, we will unmap a PUD_SIZE range.*/- if (PageHuge(page)) {
spmd_start = address;spmd_end = spmd_start + vma_mmu_pagesize(vma);/** Check if pmd sharing is possible. If possible, we could* unmap a PUD_SIZE range. spmd_start/spmd_end will be* modified if sharing is possible.*/adjust_range_if_pmd_sharing_possible(vma, &spmd_start,&spmd_end);if (spmd_end - spmd_start != vma_mmu_pagesize(vma)) {sh_address = address;pmd_sharing_possible = true;mmu_notifier_invalidate_range_start(vma->vm_mm,spmd_start, spmd_end);}- }
- pte = page_check_address(page, mm, address, &ptl, 0); if (!pte) goto out;
@@ -1356,6 +1385,30 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } }
- /*
* Call huge_pmd_unshare to potentially unshare a huge pmd. Pass* sh_address as it will be modified if unsharing is successful.*/- if (PageHuge(page) && huge_pmd_unshare(mm, &sh_address, pte)) {
/** huge_pmd_unshare unmapped an entire PMD page. There is* no way of knowing exactly which PMDs may be cached for* this mm, so flush them all. spmd_start/spmd_end cover* this PUD_SIZE range.*/flush_cache_range(vma, spmd_start, spmd_end);flush_tlb_range(vma, spmd_start, spmd_end);/** The ref count of the PMD page was dropped which is part* of the way map counting is done for shared PMDs. When* there is no other sharing, huge_pmd_unshare returns false* and we will unmap the actual page and drop map count* to zero.*/goto out_unmap;- }
- /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); if (should_defer_flush(mm, flags)) {
@@ -1450,6 +1503,9 @@ out_unmap: if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK)) mmu_notifier_invalidate_page(mm, address); out:
- if (pmd_sharing_possible)
mmu_notifier_invalidate_range_end(vma->vm_mm,spmd_start, spmd_end);} -- 2.17.2
Now queued up, thanks.
greg k-h
linux-stable-mirror@lists.linaro.org
-
Greg KH -
gregkh＠linuxfoundation.org
-
Jerome Glisse -
Michal Hocko -
Mike Kravetz