Commit a9659476 authored Jul 11, 2019 by Nicolas Boichat Committed by Linus Torvalds Jul 12, 2019

mm/failslab.c: by default, do not fail allocations with direct reclaim only

When failslab was originally written, the intention of the
"ignore-gfp-wait" flag default value ("N") was to fail GFP_ATOMIC
allocations.  Those were defined as (__GFP_HIGH), and the code would test
for __GFP_WAIT (0x10u).

However, since then, __GFP_WAIT was replaced by __GFP_RECLAIM
(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM), and GFP_ATOMIC is now
defined as (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM).

This means that when the flag is false, almost no allocation ever fails
(as even GFP_ATOMIC allocations contain ___GFP_KSWAPD_RECLAIM).

Restore the original intent of the code, by ignoring calls that directly
reclaim only (__GFP_DIRECT_RECLAIM), and thus, failing GFP_ATOMIC calls
again by default.

Link: http://lkml.kernel.org/r/20190520214514.81360-1-drinkcat@chromium.org


Fixes: 71baba4b ("mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM")
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f4458845

mm/failslab.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -23,7 +23,8 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
		if (gfpflags & __GFP_NOFAIL)
		return false;

		if (failslab.ignore_gfp_reclaim && (gfpflags & __GFP_RECLAIM))
		if (failslab.ignore_gfp_reclaim &&
		(gfpflags & __GFP_DIRECT_RECLAIM))
		return false;

		if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB))

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