We set the BTRFS_BALANCE_RESUME flag in the btrfs_recover_balance(),
which is not called during the remount. So when resuming from the
paused balance we hit BUG.
kernel: kernel BUG at fs/btrfs/volumes.c:3890!
::
kernel: balance_kthread+0x51/0x60 [btrfs]
kernel: kthread+0x111/0x130
::
kernel: RIP: btrfs_balance+0x12e1/0x1570 [btrfs] RSP: ffffba7d0090bde8
Reproducer:
On a mounted BTRFS.
btrfs balance start --full-balance /btrfs
btrfs balance pause /btrfs
mount -o remount,ro /dev/sdb /btrfs
mount -o remount,rw /dev/sdb /btrfs
To fix this set the BTRFS_BALANCE_RESUME flag in btrfs_resume_balance_async()
instead of btrfs_recover_balance().
Signed-off-by: Anand Jain <anand.j...@oracle.com>
---
v1->v2: btrfs_resume_balance_async() can be called only from remount or
mount, we don't need to hold fs_info->balance_lock.
Strictly speaking we should rather keep the balance at the paused state
unless it is resumed by the user again, that means neither mount nor
remount-rw should resume the balance automatically, former case needs
writing balance status to the disk. Which needs compatibility
verification. So for now just avoid BUG.
fs/btrfs/volumes.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3e6983a169c4..64bcaf25908b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4115,6 +4115,8 @@ int btrfs_resume_balance_async(struct btrfs_fs_info
*fs_info)
return 0;
}
+ fs_info->balance_ctl->b_flags |= BTRFS_BALANCE_RESUME;
+
tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
return PTR_ERR_OR_ZERO(tsk);
}
@@ -4156,7 +4158,6 @@ int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
bctl->fs_info = fs_info;
bctl->flags = btrfs_balance_flags(leaf, item);
- bctl->flags |= BTRFS_BALANCE_RESUME;
btrfs_balance_data(leaf, item, &disk_bargs);
btrfs_disk_balance_args_to_cpu(&bctl->data, &disk_bargs);
--
2.7.0
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