[PATCH] selinux: replace GFP_ATOMIC | __GFP_NOMEMALLOC with GFP_NOWAIT

[Michal Hocko]

selinux avc code uses a weird combination of gfp flags. It asks for
GFP_ATOMIC which allows access to memory reserves while it requests
to not consume memory reserves by __GFP_NOMEMALLOC. This seems to be
copying the pattern from 6290c2c43973 ("selinux: tag avc cache alloc as
non-critical").

Back then (before d0164adc89f6 ("mm, page_alloc: distinguish between
being unable to sleep, unwilling to sleep and avoiding waking kswapd"))
we didn't have a good way to distinguish nowait and atomic allocations
so the construct made some sense. Now we do not have to play tricks
though and GFP_NOWAIT will provide the required semantic (aka do not
sleep and do not consume any memory reserves).

Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 security/selinux/avc.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 4b4293194aee..b2c159e832b6 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -346,27 +346,26 @@ static struct avc_xperms_decision_node
 	struct avc_xperms_decision_node *xpd_node;
 	struct extended_perms_decision *xpd;
 
-	xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
-				GFP_ATOMIC | __GFP_NOMEMALLOC);
+	xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep, GFP_NOWAIT);
 	if (!xpd_node)
 		return NULL;
 
 	xpd = &xpd_node->xpd;
 	if (which & XPERMS_ALLOWED) {
 		xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
-						GFP_ATOMIC | __GFP_NOMEMALLOC);
+						GFP_NOWAIT);
 		if (!xpd->allowed)
 			goto error;
 	}
 	if (which & XPERMS_AUDITALLOW) {
 		xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
-						GFP_ATOMIC | __GFP_NOMEMALLOC);
+						GFP_NOWAIT);
 		if (!xpd->auditallow)
 			goto error;
 	}
 	if (which & XPERMS_DONTAUDIT) {
 		xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
-						GFP_ATOMIC | __GFP_NOMEMALLOC);
+						GFP_NOWAIT);
 		if (!xpd->dontaudit)
 			goto error;
 	}
@@ -394,8 +393,7 @@ static struct avc_xperms_node *avc_xperms_alloc(void)
 {
 	struct avc_xperms_node *xp_node;
 
-	xp_node = kmem_cache_zalloc(avc_xperms_cachep,
-				GFP_ATOMIC|__GFP_NOMEMALLOC);
+	xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT);
 	if (!xp_node)
 		return xp_node;
 	INIT_LIST_HEAD(&xp_node->xpd_head);
@@ -548,7 +546,7 @@ static struct avc_node *avc_alloc_node(void)
 {
 	struct avc_node *node;
 
-	node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
+	node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT);
 	if (!node)
 		goto out;
 
-- 
2.13.2

-- 
Michal Hocko
SUSE Labs