commit 9cf843e3f47c41440367062e92ab32e59ecb6a87
author Al Viro <viro@zeniv.linux.org.uk> Thu Apr 28 19:35:16 2016 -0400
committer Al Viro <viro@zeniv.linux.org.uk> Mon May 02 19:51:17 2016 -0400
tree c661c0dde1141aee43d8d406bd573d4ffcaafa95
parent 6fbd07146d99239547cd4970622c96e9cb0f3213

lookup_open(): lock the parent shared unless O_CREAT is given

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

diff --git a/fs/namei.c b/fs/namei.c
index b84e6b2..01069dd 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3084,7 +3084,7 @@
 	}
 
 retry_lookup:
-	if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
+	if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
 		error = mnt_want_write(nd->path.mnt);
 		if (!error)
 			got_write = true;
@@ -3094,9 +3094,15 @@
 		 * dropping this one anyway.
 		 */
 	}
-	inode_lock(dir->d_inode);
+	if (open_flag & O_CREAT)
+		inode_lock(dir->d_inode);
+	else
+		inode_lock_shared(dir->d_inode);
 	error = lookup_open(nd, &path, file, op, got_write, opened);
-	inode_unlock(dir->d_inode);
+	if (open_flag & O_CREAT)
+		inode_unlock(dir->d_inode);
+	else
+		inode_unlock_shared(dir->d_inode);
 
 	if (error <= 0) {
 		if (error)