[RFC PATCH 05/14] SCSI: prepare for introducing admin queue for legacy path

Ming Lei
2018-08-07T17:44:24Z

Uses scsi_is_admin_queue() and scsi_get_scsi_dev() to retrieve
'scsi_device' for legacy path.

The same approach can be used in SCSI_MQ path too, just not
efficiently, and will deal with this issue when introducing admin
queue for SCSI_MQ.

Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
drivers/scsi/scsi_lib.c | 32 +++++++++++++++++++++++++++-----
1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 62699adaef61..435347f58328 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -46,6 +46,20 @@ static DEFINE_MUTEX(scsi_sense_cache_mutex);

static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd);

+/* For admin queue, its queuedata is NULL */
+static inline bool scsi_is_admin_queue(struct request_queue *q)
+{
+ return !q->queuedata;
+}
+
+/* This helper can only be used in req prep stage */
+static inline struct scsi_device *scsi_get_scsi_dev(struct request *rq)
+{
+ if (scsi_is_admin_queue(rq->q))
+ return scsi_req(rq)->sdev;
+ return rq->q->queuedata;
+}
+
static inline struct kmem_cache *
scsi_select_sense_cache(bool unchecked_isa_dma)
{
@@ -1378,7 +1392,7 @@ scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
static int
scsi_prep_return(struct request_queue *q, struct request *req, int ret)
{
- struct scsi_device *sdev = q->queuedata;
+ struct scsi_device *sdev = scsi_get_scsi_dev(req);

switch (ret) {
case BLKPREP_KILL:
@@ -1411,7 +1425,7 @@ scsi_prep_return(struct request_queue *q, struct request *req, int ret)

static int scsi_prep_fn(struct request_queue *q, struct request *req)
{
- struct scsi_device *sdev = q->queuedata;
+ struct scsi_device *sdev = scsi_get_scsi_dev(req);
struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
int ret;

@@ -1613,6 +1627,9 @@ static int scsi_lld_busy(struct request_queue *q)
if (blk_queue_dying(q))
return 0;

+ if (WARN_ON_ONCE(scsi_is_admin_queue(q)))
+ return 0;
+
shost = sdev->host;

/*
@@ -1816,7 +1833,7 @@ static void scsi_request_fn(struct request_queue *q)
__releases(q->queue_lock)
__acquires(q->queue_lock)
{
- struct scsi_device *sdev = q->queuedata;
+ struct scsi_device *sdev;
struct Scsi_Host *shost;
struct scsi_cmnd *cmd;
struct request *req;
@@ -1825,7 +1842,6 @@ static void scsi_request_fn(struct request_queue *q)
* To start with, we keep looping until the queue is empty, or until
* the host is no longer able to accept any more requests.
*/
- shost = sdev->host;
for (;;) {
int rtn;
/*
@@ -1837,6 +1853,10 @@ static void scsi_request_fn(struct request_queue *q)
if (!req)
break;

+ cmd = blk_mq_rq_to_pdu(req);
+ sdev = cmd->device;
+ shost = sdev->host;
+
if (unlikely(!scsi_device_online(sdev))) {
sdev_printk(KERN_ERR, sdev,
"rejecting I/O to offline device\n");
@@ -1854,7 +1874,6 @@ static void scsi_request_fn(struct request_queue *q)
blk_start_request(req);

spin_unlock_irq(q->queue_lock);
- cmd = blk_mq_rq_to_pdu(req);
if (cmd != req->special) {
printk(KERN_CRIT "impossible request in %s.\n"
"please mail a stack trace to "
@@ -2332,6 +2351,9 @@ struct scsi_device *scsi_device_from_queue(struct request_queue *q)
{
struct scsi_device *sdev = NULL;

+ /* admin queue won't be exposed to external users */
+ WARN_ON_ONCE(scsi_is_admin_queue(q));
+
if (q->mq_ops) {
if (q->mq_ops == &scsi_mq_ops)
sdev = q->queuedata;
--
2.9.5