Btrfs: set right total device count for seeding support

commit 298658414a2f0bea1f05a81876a45c1cd96aa2e0 upstream.

Seeding device support allows us to create a new filesystem
based on existed filesystem.

However newly created filesystem's @total_devices should include seed
devices. This patch fix the following problem:

 # mkfs.btrfs -f /dev/sdb
 # btrfstune -S 1 /dev/sdb
 # mount /dev/sdb /mnt
 # btrfs device add -f /dev/sdc /mnt --->fs_devices->total_devices = 1
 # umount /mnt
 # mount /dev/sdc /mnt               --->fs_devices->total_devices = 2

This is because we record right @total_devices in superblock, but
@fs_devices->total_devices is reset to be 0 in btrfs_prepare_sprout().

Fix this problem by not resetting @fs_devices->total_devices.

Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f9629f5265d35ffc0158ff55a86ae7bb0487b5cb..cd8172dcd7542bcffa1890b9a3dcfffc6db06310 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1837,7 +1837,6 @@ static int btrfs_prepare_sprout(struct btrfs_root *root)
        fs_devices->seeding = 0;
        fs_devices->num_devices = 0;
        fs_devices->open_devices = 0;
-       fs_devices->total_devices = 0;
        fs_devices->seed = seed_devices;
 
        generate_random_uuid(fs_devices->fsid);