[PATCH v21 09/12] scsi: sd: Increase retry count for zoned writes

[Bart Van Assche <bvanassche@acm.org>]

If the write order is preserved, increase the number of retries for
write commands sent to a sequential zone to the maximum number of
outstanding commands because in the worst case the number of times
reordered zoned writes have to be retried is (number of outstanding
writes per sequential zone) - 1.

Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/sd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index eeaa6af294b8..587d91a9e10c 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1404,6 +1404,13 @@ static blk_status_t sd_setup_read_write_cmnd(struct scsi_cmnd *cmd)
 	cmd->transfersize = sdp->sector_size;
 	cmd->underflow = nr_blocks << 9;
 	cmd->allowed = sdkp->max_retries;
+	/*
+	 * Increase the number of allowed retries for zoned writes if the driver
+	 * preserves the command order.
+	 */
+	if (rq->q->limits.features & BLK_FEAT_ORDERED_HWQ &&
+	    blk_rq_is_seq_zoned_write(rq))
+		cmd->allowed += rq->q->nr_requests;
 	cmd->sdb.length = nr_blocks * sdp->sector_size;
 
 	SCSI_LOG_HLQUEUE(1,