-----Original Message----- From: Dexuan Cui decui@microsoft.com Sent: Thursday, October 7, 2021 1:50 PM To: KY Srinivasan kys@microsoft.com; Stephen Hemminger sthemmin@microsoft.com; wei.liu@kernel.org; jejb@linux.ibm.com; martin.petersen@oracle.com; Haiyang Zhang haiyangz@microsoft.com; ming.lei@redhat.com; bvanassche@acm.org; john.garry@huawei.com; linux- scsi@vger.kernel.org; linux-hyperv@vger.kernel.org; Long Li longli@microsoft.com; Michael Kelley mikelley@microsoft.com Cc: linux-kernel@vger.kernel.org; Dexuan Cui decui@microsoft.com; stable@vger.kernel.org Subject: [PATCH v2] scsi: core: Fix shost->cmd_per_lun calculation in scsi_add_host_with_dma()
After commit ea2f0f77538c, a 416-CPU VM running on Hyper-V hangs during boot because scsi_add_host_with_dma() sets shost->cmd_per_lun to a negative number (the below numbers may differ in different kernel versions): in drivers/scsi/storvsc_drv.c, storvsc_drv_init() sets 'max_outstanding_req_per_channel' to 352, and storvsc_probe() sets 'max_sub_channels' to (416 - 1) / 4 = 103 and sets scsi_driver.can_queue to 352 * (103 + 1) * (100 - 10) / 100 = 32947, which exceeds SHRT_MAX.
Use min_t(int, ...) to fix the issue.
Fixes: ea2f0f77538c ("scsi: core: Cap scsi_host cmd_per_lun at can_queue") Cc: stable@vger.kernel.org Signed-off-by: Dexuan Cui decui@microsoft.com
v1 tried to fix the issue by changing the storvsc driver: https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Flwn.ne t%2Fml%2Flinux- kernel%2FBYAPR21MB1270BBC14D5F1AE69FC31A16BFB09%40BYAPR21MB1270.namprd21 .prod.outlook.com%2F&data=04%7C01%7Chaiyangz%40microsoft.com%7C366e6 d0bf755492c631c08d989baf4b9%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7 C637692258384408217%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoi V2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=RbNgx1aBBBzfHC3p EdKyBZWaaQIQXS3U%2FItEQUe4NfQ%3D&reserved=0
v2 directly fixes the scsi core change instead as Michael Kelley and John Garry suggested (refer to the above link).
drivers/scsi/hosts.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c index 3f6f14f0cafb..24b72ee4246f 100644 --- a/drivers/scsi/hosts.c +++ b/drivers/scsi/hosts.c @@ -220,7 +220,8 @@ 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,
- /* Use min_t(int, ...) in case shost->can_queue exceeds SHRT_MAX */
- shost->cmd_per_lun = min_t(int, shost->cmd_per_lun, shost->can_queue);
Since shost->can_queue is int, the min_t type should also be int (the longer type of the two vars).
Reviewed-by: Haiyang Zhang haiyangz@microsoft.com