[PATCH 01/31] Split scsi_internal_device_block()

Bart Van Assche
2017-05-24T00:33:50Z

Instead of passing a "wait" argument to scsi_internal_device_block(),
split this function into a function that waits and a function that
doesn't wait. This will make it easier to serialize SCSI device state
changes through a mutex.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
---
drivers/scsi/mpt3sas/mpt3sas_scsih.c | 4 +-
drivers/scsi/scsi_lib.c | 73 +++++++++++++++++++++++-------------
include/scsi/scsi_device.h | 2 +-
3 files changed, 50 insertions(+), 29 deletions(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index a5d872664257..c63bc5ccce37 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -2859,7 +2859,7 @@ _scsih_internal_device_block(struct scsi_device *sdev,
sas_device_priv_data->sas_target->handle);
sas_device_priv_data->block = 1;

- r = scsi_internal_device_block(sdev, false);
+ r = scsi_internal_device_block_nowait(sdev);
if (r == -EINVAL)
sdev_printk(KERN_WARNING, sdev,
"device_block failed with return(%d) for handle(0x%04x)\n",
@@ -2895,7 +2895,7 @@ _scsih_internal_device_unblock(struct scsi_device *sdev,
"performing a block followed by an unblock\n",
r, sas_device_priv_data->sas_target->handle);
sas_device_priv_data->block = 1;
- r = scsi_internal_device_block(sdev, false);
+ r = scsi_internal_device_block_nowait(sdev);
if (r)
sdev_printk(KERN_WARNING, sdev, "retried device_block "
"failed with return(%d) for handle(0x%04x)\n",
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e3f89b0e7027..74618f47a28e 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2932,28 +2932,20 @@ scsi_target_resume(struct scsi_target *starget)
EXPORT_SYMBOL(scsi_target_resume);

/**
- * scsi_internal_device_block - internal function to put a device temporarily into the SDEV_BLOCK state
- * @sdev: device to block
- * @wait: Whether or not to wait until ongoing .queuecommand() /
- * .queue_rq() calls have finished.
+ * scsi_internal_device_block_nowait - try to transition to the SDEV_BLOCK state
+ * @sdev: device to block
*
- * Block request made by scsi lld's to temporarily stop all
- * scsi commands on the specified device. May sleep.
+ * Pause SCSI command processing on the specified device. Does not sleep.
*
- * Returns zero if successful or error if not
+ * Returns zero if successful or a negative error code upon failure.
*
- * Notes:
- * This routine transitions the device to the SDEV_BLOCK state
- * (which must be a legal transition). When the device is in this
- * state, all commands are deferred until the scsi lld reenables
- * the device with scsi_device_unblock or device_block_tmo fires.
- *
- * To do: avoid that scsi_send_eh_cmnd() calls queuecommand() after
- * scsi_internal_device_block() has blocked a SCSI device and also
- * remove the rport mutex lock and unlock calls from srp_queuecommand().
+ * Notes:
+ * This routine transitions the device to the SDEV_BLOCK state (which must be
+ * a legal transition). When the device is in this state, command processing
+ * is paused until the device leaves the SDEV_BLOCK state. See also
+ * scsi_internal_device_unblock_nowait().
*/
-int
-scsi_internal_device_block(struct scsi_device *sdev, bool wait)
+int scsi_internal_device_block_nowait(struct scsi_device *sdev)
{
struct request_queue *q = sdev->request_queue;
unsigned long flags;
@@ -2973,21 +2965,50 @@ scsi_internal_device_block(struct scsi_device *sdev, bool wait)
* request queue.
*/
if (q->mq_ops) {
- if (wait)
- blk_mq_quiesce_queue(q);
- else
- blk_mq_stop_hw_queues(q);
+ blk_mq_stop_hw_queues(q);
} else {
spin_lock_irqsave(q->queue_lock, flags);
blk_stop_queue(q);
spin_unlock_irqrestore(q->queue_lock, flags);
- if (wait)
- scsi_wait_for_queuecommand(sdev);
}

return 0;
}
-EXPORT_SYMBOL_GPL(scsi_internal_device_block);
+EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
+
+/**
+ * scsi_internal_device_block - try to transition to the SDEV_BLOCK state
+ * @sdev: device to block
+ *
+ * Pause SCSI command processing on the specified device and wait until all
+ * ongoing scsi_request_fn() / scsi_queue_rq() calls have finished. May sleep.
+ *
+ * Returns zero if successful or a negative error code upon failure.
+ *
+ * Note:
+ * This routine transitions the device to the SDEV_BLOCK state (which must be
+ * a legal transition). When the device is in this state, command processing
+ * is paused until the device leaves the SDEV_BLOCK state. See also
+ * scsi_internal_device_unblock().
+ *
+ * To do: avoid that scsi_send_eh_cmnd() calls queuecommand() after
+ * scsi_internal_device_block() has blocked a SCSI device and also
+ * remove the rport mutex lock and unlock calls from srp_queuecommand().
+ */
+static int scsi_internal_device_block(struct scsi_device *sdev)
+{
+ struct request_queue *q = sdev->request_queue;
+ int err;
+
+ err = scsi_internal_device_block_nowait(sdev);
+ if (err == 0) {
+ if (q->mq_ops)
+ blk_mq_quiesce_queue(q);
+ else
+ scsi_wait_for_queuecommand(sdev);
+ }
+ return err;
+}

/**
* scsi_internal_device_unblock - resume a device after a block request
@@ -3044,7 +3065,7 @@ EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
static void
device_block(struct scsi_device *sdev, void *data)
{
- scsi_internal_device_block(sdev, true);
+ scsi_internal_device_block(sdev);
}

static int
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 05641aebd181..6ce6888f3c69 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -472,7 +472,7 @@ static inline int scsi_device_created(struct scsi_device *sdev)
sdev->sdev_state == SDEV_CREATED_BLOCK;
}

-int scsi_internal_device_block(struct scsi_device *sdev, bool wait);
+int scsi_internal_device_block_nowait(struct scsi_device *sdev);
int scsi_internal_device_unblock(struct scsi_device *sdev,
enum scsi_device_state new_state);

--
2.12.2