Limit SCSI device's queue depth to max(host->can_queue, 1024) in
scsi_change_queue_depth(). 1024 is big enough for saturating current fast
SCSI LUN(SSD or RAID volume on multiple SSDs). Also single hardware queue
depth is usually enough for saturating single LUN because per-core
performance is often considered in storage design.
This patch is needed for replacing sdev->device_busy with sbitmap which has
to be pre-allocated with reasonable max depth.
Link: https://lore.kernel.org/r/20210122023317.687987-13-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Tested-by: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
scsi_io_completion(cmd, good_bytes);
}
+
+/*
+ * 1024 is big enough for saturating the fast scsi LUN now
+ */
+static int scsi_device_max_queue_depth(struct scsi_device *sdev)
+{
+ return max_t(int, sdev->host->can_queue, 1024);
+}
+
/**
* scsi_change_queue_depth - change a device's queue depth
* @sdev: SCSI Device in question
*/
int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
{
+ depth = min_t(int, depth, scsi_device_max_queue_depth(sdev));
+
if (depth > 0) {
sdev->queue_depth = depth;
wmb();