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Commit 23918b03 authored by Trond Myklebust's avatar Trond Myklebust Committed by Linus Torvalds
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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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0cb39aa0

net/sunrpc/auth_generic.c

+18 −2
Original line number Diff line number Diff line
@@ -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)