mm: consolidate GFP_NOFAIL checks in the allocator slowpath
Tetsuo Handa has pointed out that commit 0a0337e0 ("mm, oom: rework oom detection") has subtly changed semantic for costly high order requests with __GFP_NOFAIL and withtout __GFP_REPEAT and those can fail right now. My code inspection didn't reveal any such users in the tree but it is true that this might lead to unexpected allocation failures and subsequent OOPs. __alloc_pages_slowpath wrt. GFP_NOFAIL is hard to follow currently. There are few special cases but we are lacking a catch all place to be sure we will not miss any case where the non failing allocation might fail. This patch reorganizes the code a bit and puts all those special cases under nopage label which is the generic go-to-fail path. Non failing allocations are retried or those that cannot retry like non-sleeping allocation go to the failure point directly. This should make the code flow much easier to follow and make it less error prone for future changes. While we are there we have to move the stall check up to catch potentially looping non-failing allocations. [akpm@linux-foundation.org: fix alloc_flags may-be-used-uninitalized] Link: http://lkml.kernel.org/r/20161220134904.21023-2-mhocko@kernel.org Signed-off-by:Michal Hocko <mhocko@suse.com> Acked-by:
Vlastimil Babka <vbabka@suse.cz> Acked-by:
Johannes Weiner <hannes@cmpxchg.org> Acked-by:
Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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