linux-kernel - [PATCH 3/3, v3] kernel: set_groups doesn't call groups

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Date:   Mon,  4 Dec 2017 17:03:24 -0200
From:   Thiago Rafael Becker <thiago.becker@...il.com>
To:     bfields@...ldses.org, neilb@...e.com
Cc:     linux-nfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Thiago Rafael Becker <thiago.becker@...il.com>
Subject: [PATCH 3/3, v3] kernel: set_groups doesn't call groups_sort anymore.

When the group_info is cached (e.g. sunrpc) there's the possibility
that threads calling set_groups will attempt to do so simultaneously.

Moving the responsibility of sorting to the caller of set_groups, or
in the case of nfsd, to the point where it is received from rpc.mountd
avoids this issue.

Moving it to the caller has the added benifit of a slight improvement on
the nfsd performance.

Signed-off-by: Thiago Rafael Becker <thiago.becker@...il.com>
---
 kernel/groups.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/groups.c b/kernel/groups.c
index 17073a9..8620ad3 100644
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -124,7 +124,6 @@ int groups_search(const struct group_info *group_info, kgid_t grp)
 void set_groups(struct cred *new, struct group_info *group_info)
 {
 	put_group_info(new->group_info);
-	groups_sort(group_info);
 	get_group_info(group_info);
 	new->group_info = group_info;
 }
-- 
2.9.5