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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)
tree37bd46f1d30534d8f03a186338295b653e75886c
parent5853b4f06f7b9b56f37f457d7923f7b96496074e (diff)
downloadlinux-c1530019e311c91d14b24d8e74d233152d806e45.tar.bz2
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>
-rw-r--r--fs/namei.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c
index e6cd6113872c..54fc993e3027 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));
}
}