scsi: core: Cap scsi_host cmd_per_lun at can_queue

[ 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
max_queue").

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@huawei.com
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 20bb5a7dca3cd46b83011558bd4df0ea479d9ee2..ec976b93341cf595235fe52cc0713533deeb4ec5 100644 (file)
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -213,6 +213,9 @@ 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;