From: Ebru Akagunduz Date: Tue, 26 Jul 2016 22:25:06 +0000 (-0700) Subject: mm, thp: make swapin readahead under down_read of mmap_sem X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=72695862529b4190b58c779809bc01ac55ea6605;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git mm, thp: make swapin readahead under down_read of mmap_sem Currently khugepaged makes swapin readahead under down_write. This patch supplies to make swapin readahead under down_read instead of down_write. The patch was tested with a test program that allocates 800MB of memory, writes to it, and then sleeps. The system was forced to swap out all. Afterwards, the test program touches the area by writing, it skips a page in each 20 pages of the area. [akpm@linux-foundation.org: update comment to match new code] [kirill.shutemov@linux.intel.com: passing 'vma' to hugepage_vma_revlidate() is useless] Link: http://lkml.kernel.org/r/20160530095058.GA53044@black.fi.intel.com Link: http://lkml.kernel.org/r/1466021202-61880-3-git-send-email-kirill.shutemov@linux.intel.com Link: http://lkml.kernel.org/r/1464335964-6510-4-git-send-email-ebru.akagunduz@gmail.com Link: http://lkml.kernel.org/r/1466021202-61880-2-git-send-email-kirill.shutemov@linux.intel.com Signed-off-by: Ebru Akagunduz Cc: Hugh Dickins Cc: Rik van Riel Cc: "Kirill A. Shutemov" Cc: Naoya Horiguchi Cc: Andrea Arcangeli Cc: Joonsoo Kim Cc: Cyrill Gorcunov Cc: Mel Gorman Cc: David Rientjes Cc: Vlastimil Babka Cc: Aneesh Kumar K.V Cc: Johannes Weiner Cc: Michal Hocko Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/huge_memory.c b/mm/huge_memory.c index b11351579e7a..b54559058d30 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2373,6 +2373,34 @@ static bool hugepage_vma_check(struct vm_area_struct *vma) return !(vma->vm_flags & VM_NO_THP); } +/* + * If mmap_sem temporarily dropped, revalidate vma + * before taking mmap_sem. + * Return 0 if succeeds, otherwise return none-zero + * value (scan code). + */ + +static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address) +{ + struct vm_area_struct *vma; + unsigned long hstart, hend; + + if (unlikely(khugepaged_test_exit(mm))) + return SCAN_ANY_PROCESS; + + vma = find_vma(mm, address); + if (!vma) + return SCAN_VMA_NULL; + + hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; + hend = vma->vm_end & HPAGE_PMD_MASK; + if (address < hstart || address + HPAGE_PMD_SIZE > hend) + return SCAN_ADDRESS_RANGE; + if (!hugepage_vma_check(vma)) + return SCAN_VMA_CHECK; + return 0; +} + /* * Bring missing pages in from swap, to complete THP collapse. * Only done if khugepaged_scan_pmd believes it is worthwhile. @@ -2381,7 +2409,7 @@ static bool hugepage_vma_check(struct vm_area_struct *vma) * but with mmap_sem held to protect against vma changes. */ -static void __collapse_huge_page_swapin(struct mm_struct *mm, +static bool __collapse_huge_page_swapin(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd) { @@ -2397,11 +2425,18 @@ static void __collapse_huge_page_swapin(struct mm_struct *mm, continue; swapped_in++; ret = do_swap_page(mm, vma, _address, pte, pmd, - FAULT_FLAG_ALLOW_RETRY|FAULT_FLAG_RETRY_NOWAIT, + FAULT_FLAG_ALLOW_RETRY, pteval); + /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ + if (ret & VM_FAULT_RETRY) { + down_read(&mm->mmap_sem); + /* vma is no longer available, don't continue to swapin */ + if (hugepage_vma_revalidate(mm, address)) + return false; + } if (ret & VM_FAULT_ERROR) { trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0); - return; + return false; } /* pte is unmapped now, we need to map it */ pte = pte_offset_map(pmd, _address); @@ -2409,6 +2444,7 @@ static void __collapse_huge_page_swapin(struct mm_struct *mm, pte--; pte_unmap(pte); trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1); + return true; } static void collapse_huge_page(struct mm_struct *mm, @@ -2423,7 +2459,6 @@ static void collapse_huge_page(struct mm_struct *mm, struct page *new_page; spinlock_t *pmd_ptl, *pte_ptl; int isolated = 0, result = 0; - unsigned long hstart, hend; struct mem_cgroup *memcg; unsigned long mmun_start; /* For mmu_notifiers */ unsigned long mmun_end; /* For mmu_notifiers */ @@ -2446,39 +2481,37 @@ static void collapse_huge_page(struct mm_struct *mm, goto out_nolock; } - /* - * Prevent all access to pagetables with the exception of - * gup_fast later hanlded by the ptep_clear_flush and the VM - * handled by the anon_vma lock + PG_lock. - */ - down_write(&mm->mmap_sem); - if (unlikely(khugepaged_test_exit(mm))) { - result = SCAN_ANY_PROCESS; + down_read(&mm->mmap_sem); + result = hugepage_vma_revalidate(mm, address); + if (result) goto out; - } - vma = find_vma(mm, address); - if (!vma) { - result = SCAN_VMA_NULL; - goto out; - } - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; - hend = vma->vm_end & HPAGE_PMD_MASK; - if (address < hstart || address + HPAGE_PMD_SIZE > hend) { - result = SCAN_ADDRESS_RANGE; - goto out; - } - if (!hugepage_vma_check(vma)) { - result = SCAN_VMA_CHECK; - goto out; - } pmd = mm_find_pmd(mm, address); if (!pmd) { result = SCAN_PMD_NULL; goto out; } - __collapse_huge_page_swapin(mm, vma, address, pmd); + /* + * __collapse_huge_page_swapin always returns with mmap_sem locked. + * If it fails, release mmap_sem and jump directly out. + * Continuing to collapse causes inconsistency. + */ + if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) { + up_read(&mm->mmap_sem); + goto out; + } + + up_read(&mm->mmap_sem); + /* + * Prevent all access to pagetables with the exception of + * gup_fast later handled by the ptep_clear_flush and the VM + * handled by the anon_vma lock + PG_lock. + */ + down_write(&mm->mmap_sem); + result = hugepage_vma_revalidate(mm, address); + if (result) + goto out; anon_vma_lock_write(vma->anon_vma);