* [PATCH v3] btrfs: fix BUG trying to resume balance without resume flag
@ 2018-05-17 7:16 Anand Jain
2018-05-17 12:10 ` David Sterba
0 siblings, 1 reply; 2+ messages in thread
From: Anand Jain @ 2018-05-17 7:16 UTC (permalink / raw)
To: linux-btrfs
We set the BTRFS_BALANCE_RESUME flag in the btrfs_recover_balance()
only, which isn't called during the remount. So when resuming from
the paused balance we hit the 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().
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
v2->v3: . Hold fs_info->balance_lock because in remount context there can
be more the one thread accessing the balance_ctl.
. Don't remove the BTRFS_BALANCE_RESUME set at recover_balance
as in the original code.
. Add comments.
v1->v2: btrfs_resume_balance_async() can be called only from remount or
mount, we don't need to hold fs_info->balance_lock.
fs/btrfs/volumes.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 40e4259bdd51..c68976856d87 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4112,6 +4112,15 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
return 0;
}
+ /*
+ * A remount ro->rw sequence should continue with the
+ * paused balance irrespective of who pauses it, system or
+ * the user as of now, so set the resume flag.
+ */
+ spin_lock(&fs_info->balance_lock);
+ fs_info->balance_ctl->flags |= BTRFS_BALANCE_RESUME;
+ spin_unlock(&fs_info->balance_lock);
+
tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
return PTR_ERR_OR_ZERO(tsk);
}
--
2.7.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3] btrfs: fix BUG trying to resume balance without resume flag
2018-05-17 7:16 [PATCH v3] btrfs: fix BUG trying to resume balance without resume flag Anand Jain
@ 2018-05-17 12:10 ` David Sterba
0 siblings, 0 replies; 2+ messages in thread
From: David Sterba @ 2018-05-17 12:10 UTC (permalink / raw)
To: Anand Jain; +Cc: linux-btrfs
On Thu, May 17, 2018 at 03:16:51PM +0800, Anand Jain wrote:
> We set the BTRFS_BALANCE_RESUME flag in the btrfs_recover_balance()
> only, which isn't called during the remount. So when resuming from
> the paused balance we hit the 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().
>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
> ---
> v2->v3: . Hold fs_info->balance_lock because in remount context there can
> be more the one thread accessing the balance_ctl.
> . Don't remove the BTRFS_BALANCE_RESUME set at recover_balance
> as in the original code.
> . Add comments.
> v1->v2: btrfs_resume_balance_async() can be called only from remount or
> mount, we don't need to hold fs_info->balance_lock.
>
> fs/btrfs/volumes.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 40e4259bdd51..c68976856d87 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -4112,6 +4112,15 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
> return 0;
> }
>
> + /*
> + * A remount ro->rw sequence should continue with the
> + * paused balance irrespective of who pauses it, system or
> + * the user as of now, so set the resume flag.
> + */
Please format comments to full 80 column width. Fixed.
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