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authorTrond Myklebust <Trond.Myklebust@netapp.com>2008-11-20 16:06:21 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-20 13:17:40 -0800
commit23918b03060f6e572168fdde1798a905679d2e06 (patch)
tree4e95edb5030e461a1eb82e2f1fb9cb90a3b46013 /net/sunrpc/auth_generic.c
parent0cb39aa0ac3a9dc64171b43a85d17e539d82f2d6 (diff)
downloadlinux-23918b03060f6e572168fdde1798a905679d2e06.tar.gz
SUNRPC: Fix a performance regression in the RPC authentication code
Fix a regression reported by Max Kellermann whereby kernel profiling showed that his clients were spending 45% of their time in rpcauth_lookup_credcache. It turns out that although his processes had identical uid/gid/groups, generic_match() was failing to detect this, because the task->group_info pointers were not shared. This again lead to the creation of a huge number of identical credentials at the RPC layer. The regression is fixed by comparing the contents of task->group_info if the actual pointers are not identical. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'net/sunrpc/auth_generic.c')
-rw-r--r--net/sunrpc/auth_generic.c20
1 files changed, 18 insertions, 2 deletions
diff --git a/net/sunrpc/auth_generic.c b/net/sunrpc/auth_generic.c
index 744b79fdcb1..4028502f052 100644
--- a/net/sunrpc/auth_generic.c
+++ b/net/sunrpc/auth_generic.c
@@ -133,13 +133,29 @@ static int
generic_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
{
struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
+ int i;
if (gcred->acred.uid != acred->uid ||
gcred->acred.gid != acred->gid ||
- gcred->acred.group_info != acred->group_info ||
gcred->acred.machine_cred != acred->machine_cred)
- return 0;
+ goto out_nomatch;
+
+ /* Optimisation in the case where pointers are identical... */
+ if (gcred->acred.group_info == acred->group_info)
+ goto out_match;
+
+ /* Slow path... */
+ if (gcred->acred.group_info->ngroups != acred->group_info->ngroups)
+ goto out_nomatch;
+ for (i = 0; i < gcred->acred.group_info->ngroups; i++) {
+ if (GROUP_AT(gcred->acred.group_info, i) !=
+ GROUP_AT(acred->group_info, i))
+ goto out_nomatch;
+ }
+out_match:
return 1;
+out_nomatch:
+ return 0;
}
void __init rpc_init_generic_auth(void)