path: root/include
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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2014-02-25 15:01:42 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-02-25 15:25:44 -0800
commit9845cbbd113fbb5b769a45d8e88dc47bc12df4e0 (patch)
tree6ceaa19094138fe27cc6be0009dea1ef770c762b /include
parent01412886b735ef241f9a41adf9f707ce1522eb61 (diff)
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>
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