[PATCH] scsi: sd: Add a comment about limiting max_sectors to shost optimal limit

[John Garry <john.garry@huawei.com>]

Add a comment about limiting the default the SCSI disk request_queue
max_sectors initial value to that of the SCSI host optimal sectors limit.

Suggested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: John Garry <john.garry@huawei.com>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 3eaee1f7aaca..ed9f43f9512e 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3296,6 +3296,11 @@ static int sd_revalidate_disk(struct gendisk *disk)
 				      (sector_t)BLK_DEF_MAX_SECTORS);
 	}
 
+	/*
+	 * Limit default to SCSI host optimal sector limit if set. There may be
+	 * an impact on performance for when the size of a request exceeds this
+	 * host limit.
+	 */
 	rw_max = min_not_zero(rw_max, sdp->host->opt_sectors);
 
 	/* Do not exceed controller limit */
-- 
2.35.3