Btrfs: protect devices list with its mutex

Since we've kill the bigger one volume_mutex, we need to add devices
list mutex back.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index db79fb7e7e91..92e586bc8004 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1681,16 +1681,17 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
         filemap_write_and_wait(bdev->bd_inode->i_mapping);
 
         devices = &root->fs_info->fs_devices->devices;
-        /*
-         * we have the volume lock, so we don't need the extra
-         * device list mutex while reading the list here.
-         */
+
+        mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
         list_for_each_entry(device, devices, dev_list) {
                 if (device->bdev == bdev) {
                         ret = -EEXIST;
+                        mutex_unlock(
+                                &root->fs_info->fs_devices->device_list_mutex);
                         goto error;
                 }
         }
+        mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 
         device = kzalloc(sizeof(*device), GFP_NOFS);
         if (!device) {