[PATCH V4 11/12] scsi: make sure sdev->queue_depth is <= max(shost->can_queue, 1024)

Ming Lei
2020-11-16T09:50:31Z

Limit scsi device's queue depth is less than max(host->can_queue, 1024)
in scsi_change_queue_depth(), and 1024 is big enough for saturating
current fast SCSI LUN(SSD, or raid volume on multiple SSDs).

We need this patch for replacing sdev->device_busy with sbitmap which
has to be pre-allocated with reasonable max depth.

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>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
drivers/scsi/scsi.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 24619c3bebd5..a28d48c850cf 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -214,6 +214,15 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
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
@@ -223,6 +232,8 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
*/
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();
--
2.25.4