lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:   Mon, 20 May 2019 12:49:51 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Michal Hocko <mhocko@...e.com>, Joe Perches <joe@...ches.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-mm@...ck.org, Akinobu Mita <akinobu.mita@...il.com>,
        Pekka Enberg <penberg@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mm/failslab: 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.

Fixes: 71baba4b92dc1fa1 ("mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM")
Signed-off-by: Nicolas Boichat <drinkcat@...omium.org>
---
 mm/failslab.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/failslab.c b/mm/failslab.c
index ec5aad211c5be97..33efcb60e633c0a 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

Powered by blists - more mailing lists