On Thu, Aug 25 2016 at 4:57pm -0400,
Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote:
> Ensure that bio_endio() is called if io->error == DM_ENDIO_REQUEUE and
> __noflush_suspending(md) returns false. Posting this as an RFC since I'm
> not really familiar with the dm code.
>
> Fixes: commit 2e93ccc1933d ("dm: suspend: add noflush pushback")
> Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
> Cc: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
I did reinstate bio-based multipath recently. But I just want to make
sure: you realize that dec_pending() is only ever used by bio-based DM
right? (dm-mq and .request_fn multipath are request-based)
For request-based DM's handling of DM_ENDIO_REQUEUE please see
drivers/md/dm-rq.c
> ---
> drivers/md/dm.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index fa9b1cb..6e04357 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -767,6 +767,7 @@ static void dec_pending(struct dm_io *io, int error)
> int io_error;
> struct bio *bio;
> struct mapped_device *md = io->md;
> + int noflush_suspending;
>
> /* Push-back supersedes any I/O errors */
> if (unlikely(error)) {
> @@ -782,12 +783,16 @@ static void dec_pending(struct dm_io *io, int error)
> * Target requested pushing back the I/O.
> */
> spin_lock_irqsave(&md->deferred_lock, flags);
> - if (__noflush_suspending(md))
> + noflush_suspending = __noflush_suspending(md);
> + if (noflush_suspending)
> bio_list_add_head(&md->deferred, io->bio);
> - else
> - /* noflush suspend was interrupted. */
> - io->error = -EIO;
> spin_unlock_irqrestore(&md->deferred_lock, flags);
> +
> + if (noflush_suspending)
> + return;
> +
> + /* noflush suspend was interrupted. */
> + io->error = -EIO;
> }
>
> io_error = io->error;
> @@ -795,9 +800,6 @@ static void dec_pending(struct dm_io *io, int error)
> end_io_acct(io);
> free_io(md, io);
>
> - if (io_error == DM_ENDIO_REQUEUE)
> - return;
> -
> if ((bio->bi_opf & REQ_PREFLUSH) && bio->bi_iter.bi_size) {
> /*
> * Preflush done for flush with data, reissue
bio-based DM's use of DM_ENDIO_REQUEUE is strictly confined to IFF the
target is performing no-flush suspend (in the mpath case, see
dm-mpath.c:must_push_back_bio()). Otherwise, bio-based DM multipath
queues bios local to the DM multipath target (see dm-mapth.c's
'queued_bios' list).
NOTE: dm-cache-target.c's use of DM_ENDIO_REQUEUE isn't well gaurded to
only return DM_ENDIO_REQUEUE if the target is noflush suspending. I'll
review this closer and also check with Joe.
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