From b0b9b3df27d100a975b4e8818f35382b64a5e35c Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Sat, 7 Jan 2017 15:37:31 -0800 Subject: [PATCH] mm: stop leaking PageTables 4.10-rc loadtest (even on x86, and even without THPCache) fails with "fork: Cannot allocate memory" or some such; and /proc/meminfo shows PageTables growing. Commit 953c66c2b22a ("mm: THP page cache support for ppc64") that got merged in rc1 removed the freeing of an unused preallocated pagetable after do_fault_around() has called map_pages(). This is usually a good optimization, so that the followup doesn't have to reallocate one; but it's not sufficient to shift the freeing into alloc_set_pte(), since there are failure cases (most commonly VM_FAULT_RETRY) which never reach finish_fault(). Check and free it at the outer level in do_fault(), then we don't need to worry in alloc_set_pte(), and can restore that to how it was (I cannot find any reason to pte_free() under lock as it was doing). And fix a separate pagetable leak, or crash, introduced by the same change, that could only show up on some ppc64: why does do_set_pmd()'s failure case attempt to withdraw a pagetable when it never deposited one, at the same time overwriting (so leaking) the vmf->prealloc_pte? Residue of an earlier implementation, perhaps? Delete it. Fixes: 953c66c2b22a ("mm: THP page cache support for ppc64") Cc: Aneesh Kumar K.V Cc: Kirill A. Shutemov Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Michael Neuling Cc: Paul Mackerras Cc: Balbir Singh Cc: Andrew Morton Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds --- mm/memory.c | 47 ++++++++++++++++++++--------------------------- 1 file changed, 20 insertions(+), 27 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 7d23b5050248..9f2c15cdb32c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3008,13 +3008,6 @@ static int do_set_pmd(struct vm_fault *vmf, struct page *page) ret = 0; count_vm_event(THP_FILE_MAPPED); out: - /* - * If we are going to fallback to pte mapping, do a - * withdraw with pmd lock held. - */ - if (arch_needs_pgtable_deposit() && ret == VM_FAULT_FALLBACK) - vmf->prealloc_pte = pgtable_trans_huge_withdraw(vma->vm_mm, - vmf->pmd); spin_unlock(vmf->ptl); return ret; } @@ -3055,20 +3048,18 @@ int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, ret = do_set_pmd(vmf, page); if (ret != VM_FAULT_FALLBACK) - goto fault_handled; + return ret; } if (!vmf->pte) { ret = pte_alloc_one_map(vmf); if (ret) - goto fault_handled; + return ret; } /* Re-check under ptl */ - if (unlikely(!pte_none(*vmf->pte))) { - ret = VM_FAULT_NOPAGE; - goto fault_handled; - } + if (unlikely(!pte_none(*vmf->pte))) + return VM_FAULT_NOPAGE; flush_icache_page(vma, page); entry = mk_pte(page, vma->vm_page_prot); @@ -3088,15 +3079,8 @@ int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, /* no need to invalidate: a not-present page won't be cached */ update_mmu_cache(vma, vmf->address, vmf->pte); - ret = 0; -fault_handled: - /* preallocated pagetable is unused: free it */ - if (vmf->prealloc_pte) { - pte_free(vmf->vma->vm_mm, vmf->prealloc_pte); - vmf->prealloc_pte = 0; - } - return ret; + return 0; } @@ -3360,15 +3344,24 @@ static int do_shared_fault(struct vm_fault *vmf) static int do_fault(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; + int ret; /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */ if (!vma->vm_ops->fault) - return VM_FAULT_SIGBUS; - if (!(vmf->flags & FAULT_FLAG_WRITE)) - return do_read_fault(vmf); - if (!(vma->vm_flags & VM_SHARED)) - return do_cow_fault(vmf); - return do_shared_fault(vmf); + ret = VM_FAULT_SIGBUS; + else if (!(vmf->flags & FAULT_FLAG_WRITE)) + ret = do_read_fault(vmf); + else if (!(vma->vm_flags & VM_SHARED)) + ret = do_cow_fault(vmf); + else + ret = do_shared_fault(vmf); + + /* preallocated pagetable is unused: free it */ + if (vmf->prealloc_pte) { + pte_free(vma->vm_mm, vmf->prealloc_pte); + vmf->prealloc_pte = 0; + } + return ret; } static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma, -- 2.20.1