commit: c1530019e311c91d14b24d8e74d233152d806e45 From: Tim Chen <[email protected]> Date: Fri, 15 Apr 2011 11:39:29 -0700 Subject: [PATCH] vfs: Fix absolute RCU path walk failures due to uninitialized seq number
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 <[email protected]> Reviewed-by: Andi Kleen <[email protected]> Cc: [email protected] (v2.6.38) Signed-off-by: Linus Torvalds <[email protected]> --- fs/namei.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index e6cd611..54fc993 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -697,6 +697,7 @@ 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)); } } _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
