mm: introduce memalloc_noreclaim_{save,restore}
The previous patch ("mm: prevent potential recursive reclaim due to
clearing PF_MEMALLOC") has shown that simply setting and clearing
PF_MEMALLOC in current->flags can result in wrongly clearing a
pre-existing PF_MEMALLOC flag and potentially lead to recursive reclaim.
Let's introduce helpers that support proper nesting by saving the
previous stat of the flag, similar to the existing memalloc_noio_* and
memalloc_nofs_* helpers. Convert existing setting/clearing of
PF_MEMALLOC within mm to the new helpers.
There are no known issues with the converted code, but the change makes
it more robust.
Link: http://lkml.kernel.org/r/20170405074700.29871-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Suggested-by: Michal Hocko <mhocko@suse.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: Andrey Ryabinin <aryabinin@virtuozzo.com>
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1daf509..f9e450c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3283,15 +3283,15 @@ __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;
+ unsigned int noreclaim_flag;
if (!order)
return NULL;
- current->flags |= PF_MEMALLOC;
+ noreclaim_flag = memalloc_noreclaim_save();
*compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
prio);
- current->flags = (current->flags & ~PF_MEMALLOC) | noreclaim_flag;
+ memalloc_noreclaim_restore(noreclaim_flag);
if (*compact_result <= COMPACT_INACTIVE)
return NULL;
@@ -3438,12 +3438,13 @@ __perform_reclaim(gfp_t gfp_mask, unsigned int order,
{
struct reclaim_state reclaim_state;
int progress;
+ unsigned int noreclaim_flag;
cond_resched();
/* We now go into synchronous reclaim */
cpuset_memory_pressure_bump();
- current->flags |= PF_MEMALLOC;
+ noreclaim_flag = memalloc_noreclaim_save();
lockdep_set_current_reclaim_state(gfp_mask);
reclaim_state.reclaimed_slab = 0;
current->reclaim_state = &reclaim_state;
@@ -3453,7 +3454,7 @@ __perform_reclaim(gfp_t gfp_mask, unsigned int order,
current->reclaim_state = NULL;
lockdep_clear_current_reclaim_state();
- current->flags &= ~PF_MEMALLOC;
+ memalloc_noreclaim_restore(noreclaim_flag);
cond_resched();