On Thu, 2019-04-04 at 16:43 +-0800, Ming Lei wrote: +AD4 scsi+AF8-device's refcount is always grabbed in IO path. +AD4 +AD4 Turns out it isn't necessary, because blk+AF8-queue+AF8-cleanup() will +AD4 drain any in-flight IOs, then cancel timeout/requeue work, and +AD4 SCSI's requeue+AF8-work is canceled too in +AF8AXw-scsi+AF8-remove+AF8-device(). +AD4 +AD4 Also scsi+AF8-device won't go away until blk+AF8-cleanup+AF8-queue() is done. +AD4 +AD4 So don't hold the refcount in IO path, especially the refcount isn't +AD4 required in IO path since blk+AF8-queue+AF8-enter() / blk+AF8-queue+AF8-exit() +AD4 is introduced in the legacy block layer. +AD4 +AD4 Cc: Dongli Zhang +ADw-dongli.zhang+AEA-oracle.com+AD4 +AD4 Cc: James Smart +ADw-james.smart+AEA-broadcom.com+AD4 +AD4 Cc: Bart Van Assche +ADw-bart.vanassche+AEA-wdc.com+AD4 +AD4 Cc: linux-scsi+AEA-vger.kernel.org, +AD4 Cc: Martin K . Petersen +ADw-martin.petersen+AEA-oracle.com+AD4, +AD4 Cc: Christoph Hellwig +ADw-hch+AEA-lst.de+AD4, +AD4 Cc: James E . J . Bottomley +ADw-jejb+AEA-linux.vnet.ibm.com+AD4, +AD4 Cc: jianchao wang +ADw-jianchao.w.wang+AEA-oracle.com+AD4 +AD4 Signed-off-by: Ming Lei +ADw-ming.lei+AEA-redhat.com+AD4 +AD4 --- +AD4 drivers/scsi/scsi+AF8-lib.c +AHw 28 +-+--------------------------- +AD4 1 file changed, 2 insertions(+-), 26 deletions(-) +AD4 +AD4 diff --git a/drivers/scsi/scsi+AF8-lib.c b/drivers/scsi/scsi+AF8-lib.c +AD4 index 601b9f1de267..3369d66911eb 100644 +AD4 --- a/drivers/scsi/scsi+AF8-lib.c +AD4 +-+-+- b/drivers/scsi/scsi+AF8-lib.c +AD4 +AEAAQA -141,8 +-141,6 +AEAAQA scsi+AF8-set+AF8-blocked(struct scsi+AF8-cmnd +ACo-cmd, int reason) +AD4 +AD4 static void scsi+AF8-mq+AF8-requeue+AF8-cmd(struct scsi+AF8-cmnd +ACo-cmd) +AD4 +AHs +AD4 - struct scsi+AF8-device +ACo-sdev +AD0 cmd-+AD4-device+ADs +AD4 - +AD4 if (cmd-+AD4-request-+AD4-rq+AF8-flags +ACY RQF+AF8-DONTPREP) +AHs +AD4 cmd-+AD4-request-+AD4-rq+AF8-flags +ACYAPQ +AH4-RQF+AF8-DONTPREP+ADs +AD4 scsi+AF8-mq+AF8-uninit+AF8-cmd(cmd)+ADs +AD4 +AEAAQA -150,7 +-148,6 +AEAAQA static void scsi+AF8-mq+AF8-requeue+AF8-cmd(struct scsi+AF8-cmnd +ACo-cmd) +AD4 WARN+AF8-ON+AF8-ONCE(true)+ADs +AD4 +AH0 +AD4 blk+AF8-mq+AF8-requeue+AF8-request(cmd-+AD4-request, true)+ADs +AD4 - put+AF8-device(+ACY-sdev-+AD4-sdev+AF8-gendev)+ADs +AD4 +AH0 +AD4 +AD4 /+ACoAKg +AD4 +AEAAQA -189,19 +-186,7 +AEAAQA static void +AF8AXw-scsi+AF8-queue+AF8-insert(struct scsi+AF8-cmnd +ACo-cmd, int reason, bool unbusy) +AD4 +ACo-/ +AD4 cmd-+AD4-result +AD0 0+ADs +AD4 +AD4 - /+ACo +AD4 - +ACo Before a SCSI command is dispatched, +AD4 - +ACo get+AF8-device(+ACY-sdev-+AD4-sdev+AF8-gendev) is called and the host, +AD4 - +ACo target and device busy counters are increased. Since +AD4 - +ACo requeuing a request causes these actions to be repeated and +AD4 - +ACo since scsi+AF8-device+AF8-unbusy() has already been called, +AD4 - +ACo put+AF8-device(+ACY-device-+AD4-sdev+AF8-gendev) must still be called. Call +AD4 - +ACo put+AF8-device() after blk+AF8-mq+AF8-requeue+AF8-request() to avoid that +AD4 - +ACo removal of the SCSI device can start before requeueing has +AD4 - +ACo happened. +AD4 - +ACo-/ +AD4 blk+AF8-mq+AF8-requeue+AF8-request(cmd-+AD4-request, true)+ADs +AD4 - put+AF8-device(+ACY-device-+AD4-sdev+AF8-gendev)+ADs +AD4 +AH0 +AD4 +AD4 /+ACo +AD4 +AEAAQA -619,7 +-604,6 +AEAAQA static bool scsi+AF8-end+AF8-request(struct request +ACo-req, blk+AF8-status+AF8-t error, +AD4 blk+AF8-mq+AF8-run+AF8-hw+AF8-queues(q, true)+ADs +AD4 +AD4 percpu+AF8-ref+AF8-put(+ACY-q-+AD4-q+AF8-usage+AF8-counter)+ADs +AD4 - put+AF8-device(+ACY-sdev-+AD4-sdev+AF8-gendev)+ADs +AD4 return false+ADs +AD4 +AH0 +AD4 +AD4 +AEAAQA -1613,7 +-1597,6 +AEAAQA static void scsi+AF8-mq+AF8-put+AF8-budget(struct blk+AF8-mq+AF8-hw+AF8-ctx +ACo-hctx) +AD4 struct scsi+AF8-device +ACo-sdev +AD0 q-+AD4-queuedata+ADs +AD4 +AD4 atomic+AF8-dec(+ACY-sdev-+AD4-device+AF8-busy)+ADs +AD4 - put+AF8-device(+ACY-sdev-+AD4-sdev+AF8-gendev)+ADs +AD4 +AH0 +AD4 +AD4 static bool scsi+AF8-mq+AF8-get+AF8-budget(struct blk+AF8-mq+AF8-hw+AF8-ctx +ACo-hctx) +AD4 +AEAAQA -1621,16 +-1604,9 +AEAAQA static bool scsi+AF8-mq+AF8-get+AF8-budget(struct blk+AF8-mq+AF8-hw+AF8-ctx +ACo-hctx) +AD4 struct request+AF8-queue +ACo-q +AD0 hctx-+AD4-queue+ADs +AD4 struct scsi+AF8-device +ACo-sdev +AD0 q-+AD4-queuedata+ADs +AD4 +AD4 - if (+ACE-get+AF8-device(+ACY-sdev-+AD4-sdev+AF8-gendev)) +AD4 - goto out+ADs +AD4 - if (+ACE-scsi+AF8-dev+AF8-queue+AF8-ready(q, sdev)) +AD4 - goto out+AF8-put+AF8-device+ADs +AD4 - +AD4 - return true+ADs +AD4 +- if (scsi+AF8-dev+AF8-queue+AF8-ready(q, sdev)) +AD4 +- return true+ADs +AD4 +AD4 -out+AF8-put+AF8-device: +AD4 - put+AF8-device(+ACY-sdev-+AD4-sdev+AF8-gendev)+ADs +AD4 -out: +AD4 if (atomic+AF8-read(+ACY-sdev-+AD4-device+AF8-busy) +AD0APQ 0 +ACYAJg +ACE-scsi+AF8-device+AF8-blocked(sdev)) +AD4 blk+AF8-mq+AF8-delay+AF8-run+AF8-hw+AF8-queue(hctx, SCSI+AF8-QUEUE+AF8-DELAY)+ADs +AD4 return false+ADs Reviewed-by: Bart Van Assche +ADw-bvanassche+AEA-acm.org+AD4
