From b63349a7a53d34ffde70cb4feec48ea9e6f5e97b Mon Sep 17 00:00:00 2001 From: Hannes Reinecke Date: Tue, 1 Oct 2013 11:49:56 +0200 Subject: [PATCH] dm mpath: requeue I/O during pg_init When pg_init is running no I/O can be submitted to the underlying devices, as the path priority etc might change. When using queue_io for this, requests will be piling up within multipath as the block I/O scheduler just sees a _very fast_ device. All of this queued I/O has to be resubmitted from within multipathing once pg_init is done. This approach has the problem that it's virtually impossible to abort I/O when pg_init is running, and we're adding heavy load to the devices after pg_init since all of the queued I/O needs to be resubmitted _before_ any requests can be pulled off of the request queue and normal operation continues. This patch will requeue the I/O that triggers the pg_init call, and return 'busy' when pg_init is in progress. With these changes the block I/O scheduler will stop submitting I/O during pg_init, resulting in a quicker path switch and less I/O pressure (and memory consumption) after pg_init. Signed-off-by: Hannes Reinecke [patch header edited for clarity and typos by Mike Snitzer] Signed-off-by: Mike Snitzer --- drivers/md/dm-mpath.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 799e479..6eb9dc9 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -391,13 +391,16 @@ static int map_io(struct multipath *m, struct request *clone, if (was_queued) m->queue_size--; - if ((pgpath && m->queue_io) || - (!pgpath && m->queue_if_no_path)) { + if (m->pg_init_required) { + if (!m->pg_init_in_progress) + queue_work(kmultipathd, &m->process_queued_ios); + r = DM_MAPIO_REQUEUE; + } else if ((pgpath && m->queue_io) || + (!pgpath && m->queue_if_no_path)) { /* Queue for the daemon to resubmit */ list_add_tail(&clone->queuelist, &m->queued_ios); m->queue_size++; - if ((m->pg_init_required && !m->pg_init_in_progress) || - !m->queue_io) + if (!m->queue_io) queue_work(kmultipathd, &m->process_queued_ios); pgpath = NULL; r = DM_MAPIO_SUBMITTED; @@ -1677,6 +1680,11 @@ static int multipath_busy(struct dm_target *ti) spin_lock_irqsave(&m->lock, flags); + /* pg_init in progress, requeue until done */ + if (m->pg_init_in_progress) { + busy = 1; + goto out; + } /* Guess which priority_group will be used at next mapping time */ if (unlikely(!m->current_pgpath && m->next_pg)) pg = m->next_pg; -- 2.7.4