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.
Fixes: 71baba4b92dc1fa1 ("mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM")
Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
Reviewed-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
---
mm/failslab.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/failslab.c b/mm/failslab.c
index ec5aad211c5be97..f92fed91ac2360a 100644
--- a/mm/failslab.c
+++ b/mm/failslab.c
@@ -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))
--
2.21.0.1020.gf2820cf01a-goog
