[PATCH] scsi: Only return started requests from scsi_host_find_tag()

[PATCH] scsi: Only return started requests from scsi_host_find_tag()

[Hannes Reinecke]

scsi_host_find_tag() is used by the drivers to return a scsi
command based on the command tag. Typically it's used from the
interrupt handler to fetch the command associated with a value
returned from hardware. Some drivers like fnic or qla4xxx, however,
also use it also to traverse outstanding comands.
With the current implementation scsi_host_find_tag() will return
command even if they are not started (ie passed to the driver).
This will result in random errors with those drivers.
With this patch scsi_host_find_tag() will only return 'started'
commands (ie commands which have been passed to the drivers)
thus avoiding the above issue.
The other usecases will be unaffected as the interrupt handler
naturally will only ever return 'started' requests.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 include/scsi/scsi_tcq.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index 6053d46e794e..ea7848e74d25 100644
--- a/include/scsi/scsi_tcq.h
+++ b/include/scsi/scsi_tcq.h
@@ -34,7 +34,7 @@ static inline struct scsi_cmnd *scsi_host_find_tag(struct Scsi_Host *shost,
 					blk_mq_unique_tag_to_tag(tag));
 	}
 
-	if (!req)
+	if (!req || !blk_mq_request_started(req))
 		return NULL;
 	return blk_mq_rq_to_pdu(req);
 }
-- 
2.16.4

Re: [PATCH] scsi: Only return started requests from scsi_host_find_tag()

[Martin K. Petersen]

On Mon, 22 Jun 2020 08:30:22 +0200, Hannes Reinecke wrote:

> scsi_host_find_tag() is used by the drivers to return a scsi
> command based on the command tag. Typically it's used from the
> interrupt handler to fetch the command associated with a value
> returned from hardware. Some drivers like fnic or qla4xxx, however,
> also use it also to traverse outstanding comands.
> With the current implementation scsi_host_find_tag() will return
> command even if they are not started (ie passed to the driver).
> This will result in random errors with those drivers.
> With this patch scsi_host_find_tag() will only return 'started'
> commands (ie commands which have been passed to the drivers)
> thus avoiding the above issue.
> The other usecases will be unaffected as the interrupt handler
> naturally will only ever return 'started' requests.

Applied to 5.9/scsi-queue, thanks!

[1/1] scsi: core: Only return started requests from scsi_host_find_tag()
      https://git.kernel.org/mkp/scsi/c/e73a5e8e8003

-- 
Martin K. Petersen	Oracle Linux Engineering