]> git.baikalelectronics.ru Git - kernel.git/commit
mm: consolidate GFP_NOFAIL checks in the allocator slowpath
authorMichal Hocko <mhocko@suse.com>
Wed, 22 Feb 2017 23:46:19 +0000 (15:46 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 23 Feb 2017 00:41:30 +0000 (16:41 -0800)
commit0737317cd86567b69655025137680048164f2740
tree32b8a37be77bb94f1a20f97d10d212ac0d180092
parent5d92b68f238b0a9cbd7beb38ba6c3c677207a784
mm: consolidate GFP_NOFAIL checks in the allocator slowpath

Tetsuo Handa has pointed out that commit 095538c69b23 ("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>
mm/page_alloc.c