mm, page_alloc: warn for non-blockable __GFP_NOFAIL allocation failure

__GFP_NOFAIL may return NULL when coupled with GFP_NOWAIT or GFP_ATOMIC.

Luckily, nothing currently does such craziness.  So instead of causing
such allocations to loop (potentially forever), we maintain the current
behavior and also warn about the new users of the deprecated flag.

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
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 84da0e3bc8869e625b2ad57af17ac17319ce9fcd..533e2147d14f8db9c6a6fe2090162f1e5dbff0e6 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2525,8 +2525,15 @@ rebalance:
        }
 
        /* Atomic allocations - we can't balance anything */
-       if (!wait)
+       if (!wait) {
+               /*
+                * All existing users of the deprecated __GFP_NOFAIL are
+                * blockable, so warn of any new users that actually allow this
+                * type of allocation to fail.
+                */
+               WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL);
                goto nopage;
+       }
 
        /* Avoid recursion of direct reclaim */
        if (current->flags & PF_MEMALLOC)