[PATCH 5.4 022/149] scsi: core: Cap scsi_host cmd_per_lun at can_queue

From: Greg Kroah-Hartman
Date: Mon Jul 19 2021 - 12:49:32 EST

From: John Garry <john.garry@xxxxxxxxxx>

[ Upstream commit ea2f0f77538c50739b9fb4de4700cee5535e1f77 ]

The sysfs handling function sdev_store_queue_depth() enforces that the sdev
queue depth cannot exceed shost can_queue. The initial sdev queue depth
comes from shost cmd_per_lun. However, the LLDD may manually set
cmd_per_lun to be larger than can_queue, which leads to an initial sdev
queue depth greater than can_queue.

Such an issue was reported in [0], which caused a hang. That has since been
fixed in commit fc09acb7de31 ("scsi: scsi_debug: Fix cmd_per_lun, set to

Stop this possibly happening for other drivers by capping shost cmd_per_lun
at shost can_queue.

[0] https://lore.kernel.org/linux-scsi/YHaez6iN2HHYxYOh@T590/

Link: https://lore.kernel.org/r/1621434662-173079-1-git-send-email-john.garry@xxxxxxxxxx
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/scsi/hosts.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 119c292cdb8f..7c736e4ddafe 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -219,6 +219,9 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
goto fail;

+ shost->cmd_per_lun = min_t(short, shost->cmd_per_lun,
+ shost->can_queue);
error = scsi_init_sense_cache(shost);
if (error)
goto fail;