diff options
authorTim Chen <tim.c.chen@linux.intel.com>2011-04-15 11:39:29 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-04-15 15:28:12 -0700
commitc1530019e311c91d14b24d8e74d233152d806e45 (patch)
parent5853b4f06f7b9b56f37f457d7923f7b96496074e (diff)
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 <tim.c.chen@linux.intel.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Cc: stable@kernel.org (v2.6.38) Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c
index e6cd6113872..54fc993e302 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));