Btrfs: Fix the problem that the replace destroys the seed filesystem
The seed filesystem was destroyed by the device replace, the reproduce
method is:
# mkfs.btrfs -f <dev0>
# btrfstune -S 1 <dev0>
# mount <dev0> <mnt>
# btrfs device add <dev1> <mnt>
# umount <mnt>
# mount <dev1> <mnt>
# btrfs replace start -f <dev0> <dev2> <mnt>
# umount <mnt>
# mount <dev0> <mnt>
It is because we erase the super block on the seed device. It is wrong,
we should not change anything on the seed device.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index da0e632..00c8efd 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1848,8 +1848,12 @@
if (srcdev->bdev) {
fs_info->fs_devices->open_devices--;
- /* zero out the old super */
- btrfs_scratch_superblock(srcdev);
+ /*
+ * zero out the old super if it is not writable
+ * (e.g. seed device)
+ */
+ if (srcdev->writeable)
+ btrfs_scratch_superblock(srcdev);
}
call_rcu(&srcdev->rcu, free_device);