From ca44532139514f5fb0a5a081cd8576e4abe54e65 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Fri, 22 Jan 2021 10:33:16 +0800 Subject: scsi: core: Make sure sdev->queue_depth is <= max(shost->can_queue, 1024) 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 Cc: Kashyap Desai Cc: Sumanesh Samanta Cc: Ewan D. Milne Tested-by: Sumanesh Samanta Reviewed-by: Hannes Reinecke Signed-off-by: Ming Lei Signed-off-by: Martin K. Petersen --- drivers/scsi/scsi.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'drivers/scsi/scsi.c') 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(); -- cgit