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authorMing Lei <ming.lei@redhat.com>2017-11-04 09:55:34 +0800
committerJens Axboe <axboe@kernel.dk>2017-11-04 08:19:25 -0600
commit826a70a08b1210bbfdbda812ab43eb986e25b5c2 (patch)
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parente4f36b249b4d4e7599f1cf0c8fb50f196e52677e (diff)
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SCSI: don't get target/host busy_count in scsi_mq_get_budget()
It is very expensive to atomic_inc/atomic_dec the host wide counter of host->busy_count, and it should have been avoided via blk-mq's mechanism of getting driver tag, which uses the more efficient way of sbitmap queue. Also we don't check atomic_read(&sdev->device_busy) in scsi_mq_get_budget() and don't run queue if the counter becomes zero, so IO hang may be caused if all requests are completed just before the current SCSI device is added to shost->starved_list. Fixes: 0df21c86bdbf(scsi: implement .get_budget and .put_budget for blk-mq) Reported-by: Bart Van Assche <bart.vanassche@wdc.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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