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authorMing Lei <ming.lei@redhat.com>2018-06-25 14:31:48 +0300
committerJens Axboe <axboe@kernel.dk>2018-07-09 18:07:52 +0300
commit97889f9ac24f8d2fc8e703ea7f80c162bab10d4d (patch)
treef8280901685cfc59ae03e92ea91a29a567f3b7b6 /block/blk-mq.c
parent5815839b3ca16bb1d45939270871169f6803a121 (diff)
downloadlinux-97889f9ac24f8d2fc8e703ea7f80c162bab10d4d.tar.xz
blk-mq: remove synchronize_rcu() from blk_mq_del_queue_tag_set()
We have to remove synchronize_rcu() from blk_queue_cleanup(), otherwise long delay can be caused during lun probe. For removing it, we have to avoid to iterate the set->tag_list in IO path, eg, blk_mq_sched_restart(). This patch reverts 5b79413946d (Revert "blk-mq: don't handle TAG_SHARED in restart"). Given we have fixed enough IO hang issue, and there isn't any reason to restart all queues in one tags any more, see the following reasons: 1) blk-mq core can deal with shared-tags case well via blk_mq_get_driver_tag(), which can wake up queues waiting for driver tag. 2) SCSI is a bit special because it may return BLK_STS_RESOURCE if queue, target or host is ready, but SCSI built-in restart can cover all these well, see scsi_end_request(), queue will be rerun after any request initiated from this host/target is completed. In my test on scsi_debug(8 luns), this patch may improve IOPS by 20% ~ 30% when running I/O on these 8 luns concurrently. Fixes: 705cda97ee3a ("blk-mq: Make it safe to use RCU to iterate over blk_mq_tag_set.tag_list") Cc: Omar Sandoval <osandov@fb.com> Cc: Bart Van Assche <bart.vanassche@wdc.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Martin K. Petersen <martin.petersen@oracle.com> Cc: linux-scsi@vger.kernel.org Reported-by: Andrew Jones <drjones@redhat.com> Tested-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.c')
-rw-r--r--block/blk-mq.c10
1 files changed, 2 insertions, 8 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index df84281f6af6..7c6ff13171ef 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2335,15 +2335,10 @@ static void queue_set_hctx_shared(struct request_queue *q, bool shared)
int i;
queue_for_each_hw_ctx(q, hctx, i) {
- if (shared) {
- if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
- atomic_inc(&q->shared_hctx_restart);
+ if (shared)
hctx->flags |= BLK_MQ_F_TAG_SHARED;
- } else {
- if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
- atomic_dec(&q->shared_hctx_restart);
+ else
hctx->flags &= ~BLK_MQ_F_TAG_SHARED;
- }
}
}
@@ -2374,7 +2369,6 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q)
blk_mq_update_tag_set_depth(set, false);
}
mutex_unlock(&set->tag_list_lock);
- synchronize_rcu();
INIT_LIST_HEAD(&q->tag_set_list);
}