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author | Ming Lei <ming.lei@redhat.com> | 2018-06-25 19:31:49 +0800 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2018-07-09 09:07:52 -0600 |
commit | 1311326cf4755c7ffefd20f576144ecf46d9906b (patch) | |
tree | 9f973618b2b1d61520c37a16dbb1d27399f48632 /drivers/block/drbd | |
parent | 97889f9ac24f8d2fc8e703ea7f80c162bab10d4d (diff) |
blk-mq: avoid to synchronize rcu inside blk_cleanup_queue()
SCSI probing may synchronously create and destroy a lot of request_queues
for non-existent devices. Any synchronize_rcu() in queue creation or
destroy path may introduce long latency during booting, see detailed
description in comment of blk_register_queue().
This patch removes one synchronize_rcu() inside blk_cleanup_queue()
for this case, commit c2856ae2f315d75(blk-mq: quiesce queue before freeing queue)
needs synchronize_rcu() for implementing blk_mq_quiesce_queue(), but
when queue isn't initialized, it isn't necessary to do that since
only pass-through requests are involved, no original issue in
scsi_execute() at all.
Without this patch and previous one, it may take more 20+ seconds for
virtio-scsi to complete disk probe. With the two patches, the time becomes
less than 100ms.
Fixes: c2856ae2f315d75 ("blk-mq: quiesce queue before freeing queue")
Reported-by: Andrew Jones <drjones@redhat.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
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 'drivers/block/drbd')
0 files changed, 0 insertions, 0 deletions