From 0b76f8fcb3f302aaf18c65337a472b32d8a74b67 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Fri, 15 Apr 2011 11:39:29 -0700 Subject: [PATCH] vfs: Fix absolute RCU path walk failures due to uninitialized seq number commit c1530019e311c91d14b24d8e74d233152d806e45 upstream. During RCU walk in path_lookupat and path_openat, the rcu lookup frequently failed if looking up an absolute path, because when root directory was looked up, seq number was not properly set in nameidata. We dropped out of RCU walk in nameidata_drop_rcu due to mismatch in directory entry's seq number. We reverted to slow path walk that need to take references. With the following patch, I saw a 50% increase in an exim mail server benchmark throughput on a 4-socket Nehalem-EX system. Signed-off-by: Tim Chen Reviewed-by: Andi Kleen Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/namei.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/namei.c b/fs/namei.c index a4689eb2df2..3095ca8a31a 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -712,6 +712,7 @@ static __always_inline void set_root_rcu(struct nameidata *nd) do { seq = read_seqcount_begin(&fs->seq); nd->root = fs->root; + nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq); } while (read_seqcount_retry(&fs->seq, seq)); } } -- 2.11.4.GIT