On Wed 14-01-15 10:42:40, Christoph Hellwig wrote:
> If we have dirty inodes we need to call the filesystem for it, even if the
> device has been removed and the filesystem will error out early. The
> current code does that by reassining all dirty inodes to the default
> backing_dev_info when a bdi is unlinked, but that's pretty pointless given
> that the bdi must always outlive the super block.
>
> Instead of stopping writeback at unregister time and moving inodes to the
> default bdi just keep the current bdi alive until it is destroyed. The
> containing objects of the bdi ensure this doesn't happen until all
> writeback has finished by erroring out.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Tejun Heo <tj@xxxxxxxxxx>
Looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
One nit below:
> ---
> mm/backing-dev.c | 91 +++++++++++++++-----------------------------------------
> 1 file changed, 24 insertions(+), 67 deletions(-)
>
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index 52e0c76..3ebba25 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
...
> @@ -471,37 +445,20 @@ void bdi_destroy(struct backing_dev_info *bdi)
> {
> int i;
>
> - /*
> - * Splice our entries to the default_backing_dev_info. This
> - * condition shouldn't happen. @wb must be empty at this point and
> - * dirty inodes on it might cause other issues. This workaround is
> - * added by ce5f8e779519 ("writeback: splice dirty inode entries to
> - * default bdi on bdi_destroy()") without root-causing the issue.
> - *
> - * http://lkml.kernel.org/g/1253038617-30204-11-git-send-email-jens.axboe@xxxxxxxxxx
> - * http://thread.gmane.org/gmane.linux.file-systems/35341/focus=35350
> - *
> - * We should probably add WARN_ON() to find out whether it still
> - * happens and track it down if so.
> - */
> - if (bdi_has_dirty_io(bdi)) {
> - struct bdi_writeback *dst = &default_backing_dev_info.wb;
> -
> - bdi_lock_two(&bdi->wb, dst);
> - list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
> - list_splice(&bdi->wb.b_io, &dst->b_io);
> - list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
> - spin_unlock(&bdi->wb.list_lock);
> - spin_unlock(&dst->list_lock);
> - }
> -
> - bdi_unregister(bdi);
> + bdi_wb_shutdown(bdi);
>
> + WARN_ON(!list_empty(&bdi->work_list));
> + WARN_ON(delayed_work_pending(&bdi->wb.dwork));
> WARN_ON(delayed_work_pending(&bdi->wb.dwork));
You have the warning twice here...
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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