linux-kernel - [PATCH AUTOSEL 5.4 15/63] scsi: core: Cap scsi_host cmd_per_lun at can

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Message-Id: <20210710022709.3170675-15-sashal@kernel.org>
Date:   Fri,  9 Jul 2021 22:26:21 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     John Garry <john.garry@...wei.com>, Ming Lei <ming.lei@...hat.com>,
        Bart Van Assche <bvanassche@....org>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>, linux-scsi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 15/63] scsi: core: Cap scsi_host cmd_per_lun at can_queue

From: John Garry <john.garry@...wei.com>

[ 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@...hat.com>
Reviewed-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: John Garry <john.garry@...wei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/scsi/hosts.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index ff36432c8fbc..1e0496f71e5a 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;
-- 
2.30.2