On 2018-07-12 06:09 PM, Tony Battersby wrote:
The calling convention of blk_get_request() has changed in lk 4.18;
update the comment in sg.c to match.
Fixes: ff005a066240 ("block: sanitize blk_get_request calling conventions")
Signed-off-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Acked-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
I wrote the original comment in commit 7772855a996e ("sg: fix EWOULDBLOCK
errors with scsi-mq") back in 2015.
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index cd2fdac..1b90e5a 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1741,15 +1741,11 @@ sg_start_req(Sg_request *srp, unsigned char *cmd)
*
* With scsi-mq enabled, there are a fixed number of preallocated
* requests equal in number to shost->can_queue. If all of the
- * preallocated requests are already in use, then using GFP_ATOMIC with
- * blk_get_request() will return -EWOULDBLOCK, whereas using GFP_KERNEL
- * will cause blk_get_request() to sleep until an active command
- * completes, freeing up a request. Neither option is ideal, but
- * GFP_KERNEL is the better choice to prevent userspace from getting an
- * unexpected EWOULDBLOCK.
- *
- * With scsi-mq disabled, blk_get_request() with GFP_KERNEL usually
- * does not sleep except under memory pressure.
+ * preallocated requests are already in use, then blk_get_request()
+ * will sleep until an active command completes, freeing up a request.
+ * Although waiting in an asynchronous interface is less than ideal, we
+ * do not want to use BLK_MQ_REQ_NOWAIT here because userspace might
+ * not expect an EWOULDBLOCK from this condition.
*/
rq = blk_get_request(q, hp->dxfer_direction == SG_DXFER_TO_DEV ?
REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, 0);
