On 02/03/2014 09:28 PM, Mike Snitzer wrote:
> Return early for case when no path exists, this eliminates the need for
> extra nesting for the case when a path exists (the common case).
>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> ---
> drivers/md/dm-mpath.c | 51 +++++++++++++++++++++++++++------------------------
> 1 file changed, 27 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index 971fbec..272e7d4 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -392,32 +392,35 @@ static int multipath_map(struct dm_target *ti, struct request *clone,
>
> pgpath = m->current_pgpath;
>
> - if (pgpath) {
> - if (__pgpath_busy(pgpath))
> - goto out_unlock;
> + if (!pgpath) {
> + if (!__must_push_back(m))
> + r = -EIO; /* Failed */
> + goto out_unlock;
> + }
> +
> + if (__pgpath_busy(pgpath))
> + goto out_unlock;
>
> - if (pg_ready(m)) {
> - if (set_mapinfo(m, map_context) < 0)
> - /* ENOMEM, requeue */
> - goto out_unlock;
> -
> - bdev = pgpath->path.dev->bdev;
> - clone->q = bdev_get_queue(bdev);
> - clone->rq_disk = bdev->bd_disk;
> - clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
> - mpio = map_context->ptr;
> - mpio->pgpath = pgpath;
> - mpio->nr_bytes = nr_bytes;
> - if (pgpath->pg->ps.type->start_io)
> - pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
> - &pgpath->path,
> - nr_bytes);
> - r = DM_MAPIO_REMAPPED;
> + if (pg_ready(m)) {
> + if (set_mapinfo(m, map_context) < 0)
> + /* ENOMEM, requeue */
> goto out_unlock;
> - }
> - __pg_init_all_paths(m, 0);
> - } else if (!__must_push_back(m))
> - r = -EIO; /* Failed */
> +
> + bdev = pgpath->path.dev->bdev;
> + clone->q = bdev_get_queue(bdev);
> + clone->rq_disk = bdev->bd_disk;
> + clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
> + mpio = map_context->ptr;
> + mpio->pgpath = pgpath;
> + mpio->nr_bytes = nr_bytes;
> + if (pgpath->pg->ps.type->start_io)
> + pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
> + &pgpath->path,
> + nr_bytes);
> + r = DM_MAPIO_REMAPPED;
> + goto out_unlock;
> + }
> + __pg_init_all_paths(m, 0);
>
> out_unlock:
> spin_unlock_irqrestore(&m->lock, flags);
>
But then you should be going full circle and move the now somewhat
lonely statement '__pg_init_all_paths' to the top, inverting the
if (pg_ready(m))
statement.
I'll be redoing the patchset (yet again)
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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