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author | 2014-02-25 15:01:42 -0800 | |
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committer | 2014-02-25 15:25:44 -0800 | |
commit | 9845cbbd113fbb5b769a45d8e88dc47bc12df4e0 (patch) | |
tree | 6ceaa19094138fe27cc6be0009dea1ef770c762b | |
parent | drivers/fmc/fmc-write-eeprom.c: fix decimal permissions (diff) | |
download | linux-9845cbbd113fbb5b769a45d8e88dc47bc12df4e0.tar.gz linux-9845cbbd113fbb5b769a45d8e88dc47bc12df4e0.tar.bz2 linux-9845cbbd113fbb5b769a45d8e88dc47bc12df4e0.zip |
mm, thp: fix infinite loop on memcg OOM
Masayoshi Mizuma reported a bug with the hang of an application under
the memcg limit. It happens on write-protection fault to huge zero page
If we successfully allocate a huge page to replace zero page but hit the
memcg limit we need to split the zero page with split_huge_page_pmd()
and fallback to small pages.
The other part of the problem is that VM_FAULT_OOM has special meaning
in do_huge_pmd_wp_page() context. __handle_mm_fault() expects the page
to be split if it sees VM_FAULT_OOM and it will will retry page fault
handling. This causes an infinite loop if the page was not split.
do_huge_pmd_wp_zero_page_fallback() can return VM_FAULT_OOM if it failed
to allocate one small page, so fallback to small pages will not help.
The solution for this part is to replace VM_FAULT_OOM with
VM_FAULT_FALLBACK is fallback required.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | mm/huge_memory.c | 9 | ||||
-rw-r--r-- | mm/memory.c | 14 |
2 files changed, 9 insertions, 14 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index da23eb96779f..4df39b1bde91 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1166,8 +1166,10 @@ alloc: } else { ret = do_huge_pmd_wp_page_fallback(mm, vma, address, pmd, orig_pmd, page, haddr); - if (ret & VM_FAULT_OOM) + if (ret & VM_FAULT_OOM) { split_huge_page(page); + ret |= VM_FAULT_FALLBACK; + } put_page(page); } count_vm_event(THP_FAULT_FALLBACK); @@ -1179,9 +1181,10 @@ alloc: if (page) { split_huge_page(page); put_page(page); - } + } else + split_huge_page_pmd(vma, address, pmd); + ret |= VM_FAULT_FALLBACK; count_vm_event(THP_FAULT_FALLBACK); - ret |= VM_FAULT_OOM; goto out; } diff --git a/mm/memory.c b/mm/memory.c index 5f2001a7ab31..22dfa617bddb 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3704,7 +3704,6 @@ static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, if (unlikely(is_vm_hugetlb_page(vma))) return hugetlb_fault(mm, vma, address, flags); -retry: pgd = pgd_offset(mm, address); pud = pud_alloc(mm, pgd, address); if (!pud) @@ -3742,20 +3741,13 @@ retry: if (dirty && !pmd_write(orig_pmd)) { ret = do_huge_pmd_wp_page(mm, vma, address, pmd, orig_pmd); - /* - * If COW results in an oom, the huge pmd will - * have been split, so retry the fault on the - * pte for a smaller charge. - */ - if (unlikely(ret & VM_FAULT_OOM)) - goto retry; - return ret; + if (!(ret & VM_FAULT_FALLBACK)) + return ret; } else { huge_pmd_set_accessed(mm, vma, address, pmd, orig_pmd, dirty); + return 0; } - - return 0; } } |