Btrfs: fix oops caused by the space balance and dead roots
When doing space balance and subvolume destroy at the same time, we met
the following oops:
kernel BUG at fs/btrfs/relocation.c:2247!
RIP: 0010: [<ffffffffa04cec16>] prepare_to_merge+0x154/0x1f0 [btrfs]
Call Trace:
[<ffffffffa04b5ab7>] relocate_block_group+0x466/0x4e6 [btrfs]
[<ffffffffa04b5c7a>] btrfs_relocate_block_group+0x143/0x275 [btrfs]
[<ffffffffa0495c56>] btrfs_relocate_chunk.isra.27+0x5c/0x5a2 [btrfs]
[<ffffffffa0459871>] ? btrfs_item_key_to_cpu+0x15/0x31 [btrfs]
[<ffffffffa048b46a>] ? btrfs_get_token_64+0x7e/0xcd [btrfs]
[<ffffffffa04a3467>] ? btrfs_tree_read_unlock_blocking+0xb2/0xb7 [btrfs]
[<ffffffffa049907d>] btrfs_balance+0x9c7/0xb6f [btrfs]
[<ffffffffa049ef84>] btrfs_ioctl_balance+0x234/0x2ac [btrfs]
[<ffffffffa04a1e8e>] btrfs_ioctl+0xd87/0x1ef9 [btrfs]
[<ffffffff81122f53>] ? path_openat+0x234/0x4db
[<ffffffff813c3b78>] ? __do_page_fault+0x31d/0x391
[<ffffffff810f8ab6>] ? vma_link+0x74/0x94
[<ffffffff811250f5>] vfs_ioctl+0x1d/0x39
[<ffffffff811258c8>] do_vfs_ioctl+0x32d/0x3e2
[<ffffffff811259d4>] SyS_ioctl+0x57/0x83
[<ffffffff813c3bfa>] ? do_page_fault+0xe/0x10
[<ffffffff813c73c2>] system_call_fastpath+0x16/0x1b
It is because we returned the error number if the reference of the root was 0
when doing space relocation. It was not right here, because though the root
was dead(refs == 0), but the space it held still need be relocated, or we
could not remove the block group. So in this case, we should return the root
no matter it is dead or not.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index a5a2632..4a35572 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -588,7 +588,7 @@
else
key.offset = (u64)-1;
- return btrfs_read_fs_root_no_name(fs_info, &key);
+ return btrfs_get_fs_root(fs_info, &key, false);
}
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0