On Thu 30-05-13 10:44:19, Jan Kara wrote:
> Code in blkdev.c moves a device inode to default_backing_dev_info when
> the last reference to the device is put and moves the device inode back
> to its bdi when the first reference is acquired. This includes moving to
> wb.b_dirty list if the device inode is dirty. The code however doesn't
> setup timer to wake corresponding flusher thread and while wb.b_dirty
> list is non-empty __mark_inode_dirty() will not set it up either. Thus
> periodic writeback is effectively disabled until a sync(2) call which can
> lead to unexpected data loss in case of crash or power failure.
>
> Fix the problem by setting up a timer for periodic writeback in case we
> add the first dirty inode to wb.b_dirty list in bdev_inode_switch_bdi().
>
> Reported-by: Bert De Jonghe <Bert.DeJonghe@xxxxxxxxxxxxx>
> CC: stable@xxxxxxxxxxxxxxx # >= 3.0
> Signed-off-by: Jan Kara <jack@xxxxxxx>
Jens, I'm going over my submitted patches and I don't think you've merged
this patch. Did you?
Honza
> ---
> fs/block_dev.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 2091db8..85f5c85 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -58,17 +58,24 @@ static void bdev_inode_switch_bdi(struct inode *inode,
> struct backing_dev_info *dst)
> {
> struct backing_dev_info *old = inode->i_data.backing_dev_info;
> + bool wakeup_bdi = false;
>
> if (unlikely(dst == old)) /* deadlock avoidance */
> return;
> bdi_lock_two(&old->wb, &dst->wb);
> spin_lock(&inode->i_lock);
> inode->i_data.backing_dev_info = dst;
> - if (inode->i_state & I_DIRTY)
> + if (inode->i_state & I_DIRTY) {
> + if (bdi_cap_writeback_dirty(dst) && !wb_has_dirty_io(&dst->wb))
> + wakeup_bdi = true;
> list_move(&inode->i_wb_list, &dst->wb.b_dirty);
> + }
> spin_unlock(&inode->i_lock);
> spin_unlock(&old->wb.list_lock);
> spin_unlock(&dst->wb.list_lock);
> +
> + if (wakeup_bdi)
> + bdi_wakeup_thread_delayed(dst);
> }
>
> /* Kill _all_ buffers and pagecache , dirty or not.. */
> --
> 1.8.1.4
>
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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