diff options
| author | Vlastimil Babka | 2017-05-08 15:59:46 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2017-05-08 17:15:15 -0700 |
| commit | 62be1511b1db8066220b18b7d4da2e6b9fdc69fb (patch) | |
| tree | ca0c513abfda095e443c388e5e920d01c18c908a /mm/page_alloc.c | |
| parent | 3b6521f53572d7fc1b40c93931948716a53a82ab (diff) | |
mm: prevent potential recursive reclaim due to clearing PF_MEMALLOC
Patch series "more robust PF_MEMALLOC handling"
This series aims to unify the setting and clearing of PF_MEMALLOC, which
prevents recursive reclaim. There are some places that clear the flag
unconditionally from current->flags, which may result in clearing a
pre-existing flag. This already resulted in a bug report that Patch 1
fixes (without the new helpers, to make backporting easier). Patch 2
introduces the new helpers, modelled after existing memalloc_noio_* and
memalloc_nofs_* helpers, and converts mm core to use them. Patches 3
and 4 convert non-mm code.
This patch (of 4):
__alloc_pages_direct_compact() sets PF_MEMALLOC to prevent deadlock
during page migration by lock_page() (see the comment in
__unmap_and_move()). Then it unconditionally clears the flag, which can
clear a pre-existing PF_MEMALLOC flag and result in recursive reclaim.
This was not a problem until commit a8161d1ed609 ("mm, page_alloc:
restructure direct compaction handling in slowpath"), because direct
compation was called only after direct reclaim, which was skipped when
PF_MEMALLOC flag was set.
Even now it's only a theoretical issue, as the new callsite of
__alloc_pages_direct_compact() is reached only for costly orders and
when gfp_pfmemalloc_allowed() is true, which means either
__GFP_NOMEMALLOC is in gfp_flags or in_interrupt() is true. There is no
such known context, but let's play it safe and make
__alloc_pages_direct_compact() robust for cases where PF_MEMALLOC is
already set.
Fixes: a8161d1ed609 ("mm, page_alloc: restructure direct compaction handling in slowpath")
Link: http://lkml.kernel.org/r/20170405074700.29871-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Chris Leech <cleech@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Lee Duncan <lduncan@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e7486afa7fa7..1daf509722c7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3283,6 +3283,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, enum compact_priority prio, enum compact_result *compact_result) { struct page *page; + unsigned int noreclaim_flag = current->flags & PF_MEMALLOC; if (!order) return NULL; @@ -3290,7 +3291,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, current->flags |= PF_MEMALLOC; *compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac, prio); - current->flags &= ~PF_MEMALLOC; + current->flags = (current->flags & ~PF_MEMALLOC) | noreclaim_flag; if (*compact_result <= COMPACT_INACTIVE) return NULL; |