btrfs: lift uuid_mutex to callers of btrfs_open_devices

Prepartory work to fix race between mount and device scan.

The callers will have to manage the critical section, eg. mount wants to
scan and then call btrfs_open_devices without the ioctl scan walking in
and modifying the fs devices in the meantime.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 0b6567f..d470eb6 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1567,7 +1567,9 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
                goto error_fs_info;
        }
 
+       mutex_lock(&uuid_mutex);
        error = btrfs_open_devices(fs_devices, mode, fs_type);
+       mutex_unlock(&uuid_mutex);
        if (error)
                goto error_fs_info;
 

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index df5dd6f..459cc2a 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1142,7 +1142,8 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 {
        int ret;
 
-       mutex_lock(&uuid_mutex);
+       lockdep_assert_held(&uuid_mutex);
+
        mutex_lock(&fs_devices->device_list_mutex);
        if (fs_devices->opened) {
                fs_devices->opened++;
@@ -1152,7 +1153,6 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
                ret = open_fs_devices(fs_devices, flags, holder);
        }
        mutex_unlock(&fs_devices->device_list_mutex);
-       mutex_unlock(&uuid_mutex);
 
        return ret;
 }