Commit 669f0441 authored by Bart Van Assche's avatar Bart Van Assche Committed by Martin K. Petersen
Browse files

scsi: srp_transport: Move queuecommand() wait code to SCSI core 



Additionally, rename srp_wait_for_queuecommand() into
scsi_wait_for_queuecommand() and add a comment about the queuecommand()
call from scsi_send_eh_cmnd().

Note: this patch changes scsi_internal_device_block from a function that
did not sleep into a function that may sleep. This is fine for all
callers of this function:

* scsi_internal_device_block() is called from the mpt3sas device while
  that driver holds the ioc->dm_cmds.mutex. This means that the mpt3sas
  driver calls this function from thread context.
* scsi_target_block() is called by __iscsi_block_session() from
  kernel thread context and with IRQs enabled.
* The SRP transport code also calls scsi_target_block() from kernel
  thread context while sleeping is allowed.
* The snic driver also calls scsi_target_block() from a context from
  which sleeping is allowed. The scsi_target_block() call namely occurs
  immediately after a scsi_flush_work() call.

[mkp: s/shost/sdev/]

Signed-off-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: default avatarSagi Grimberg <sagi@grimberg.me>
Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Cc: James Bottomley <jejb@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Doug Ledford <dledford@redhat.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 27c3d768

drivers/scsi/scsi_lib.c

+39 −2
Original line number Diff line number Diff line
@@ -2733,6 +2733,39 @@ void sdev_evt_send_simple(struct scsi_device *sdev, 
}

EXPORT_SYMBOL_GPL(sdev_evt_send_simple);



/**

 * scsi_request_fn_active() - number of kernel threads inside scsi_request_fn()

 * @sdev: SCSI device to count the number of scsi_request_fn() callers for.

 */

static int scsi_request_fn_active(struct scsi_device *sdev)

{

	struct request_queue *q = sdev->request_queue;

	int request_fn_active;



	WARN_ON_ONCE(sdev->host->use_blk_mq);



	spin_lock_irq(q->queue_lock);

	request_fn_active = q->request_fn_active;

	spin_unlock_irq(q->queue_lock);



	return request_fn_active;

}



/**

 * scsi_wait_for_queuecommand() - wait for ongoing queuecommand() calls

 * @sdev: SCSI device pointer.

 *

 * Wait until the ongoing shost->hostt->queuecommand() calls that are

 * invoked from scsi_request_fn() have finished.

 */

static void scsi_wait_for_queuecommand(struct scsi_device *sdev)

{

	WARN_ON_ONCE(sdev->host->use_blk_mq);



	while (scsi_request_fn_active(sdev))

		msleep(20);

}



/**

 *	scsi_device_quiesce - Block user issued commands.

 *	@sdev:	scsi device to quiesce.
@@ -2817,8 +2850,7 @@ EXPORT_SYMBOL(scsi_target_resume); 
 * @sdev:	device to block

 *

 * Block request made by scsi lld's to temporarily stop all

 * scsi commands on the specified device.  Called from interrupt

 * or normal process context.

 * scsi commands on the specified device. May sleep.

 *

 * Returns zero if successful or error if not

 *
@@ -2827,6 +2859,10 @@ EXPORT_SYMBOL(scsi_target_resume); 
 *	(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().

 */

int

scsi_internal_device_block(struct scsi_device *sdev)
@@ -2854,6 +2890,7 @@ scsi_internal_device_block(struct scsi_device *sdev) 
		spin_lock_irqsave(q->queue_lock, flags);

		blk_stop_queue(q);

		spin_unlock_irqrestore(q->queue_lock, flags);

		scsi_wait_for_queuecommand(sdev);

	}



	return 0;

drivers/scsi/scsi_transport_srp.c

+6 −35
Original line number Diff line number Diff line
@@ -24,7 +24,6 @@ 
#include <linux/err.h>

#include <linux/slab.h>

#include <linux/string.h>

#include <linux/delay.h>



#include <scsi/scsi.h>

#include <scsi/scsi_cmnd.h>
@@ -393,36 +392,6 @@ static void srp_reconnect_work(struct work_struct *work) 
	}

}



/**

 * scsi_request_fn_active() - number of kernel threads inside scsi_request_fn()

 * @shost: SCSI host for which to count the number of scsi_request_fn() callers.

 *

 * To do: add support for scsi-mq in this function.

 */

static int scsi_request_fn_active(struct Scsi_Host *shost)

{

	struct scsi_device *sdev;

	struct request_queue *q;

	int request_fn_active = 0;



	shost_for_each_device(sdev, shost) {

		q = sdev->request_queue;



		spin_lock_irq(q->queue_lock);

		request_fn_active += q->request_fn_active;

		spin_unlock_irq(q->queue_lock);

	}



	return request_fn_active;

}



/* Wait until ongoing shost->hostt->queuecommand() calls have finished. */

static void srp_wait_for_queuecommand(struct Scsi_Host *shost)

{

	while (scsi_request_fn_active(shost))

		msleep(20);

}



static void __rport_fail_io_fast(struct srp_rport *rport)

{

	struct Scsi_Host *shost = rport_to_shost(rport);
@@ -432,15 +401,18 @@ static void __rport_fail_io_fast(struct srp_rport *rport) 


	if (srp_rport_set_state(rport, SRP_RPORT_FAIL_FAST))

		return;

	/*

	 * Call scsi_target_block() to wait for ongoing shost->queuecommand()

	 * calls before invoking i->f->terminate_rport_io().

	 */

	scsi_target_block(rport->dev.parent);

	scsi_target_unblock(rport->dev.parent, SDEV_TRANSPORT_OFFLINE);



	/* Involve the LLD if possible to terminate all I/O on the rport. */

	i = to_srp_internal(shost->transportt);

	if (i->f->terminate_rport_io) {

		srp_wait_for_queuecommand(shost);

	if (i->f->terminate_rport_io)

		i->f->terminate_rport_io(rport);

}

}



/**

 * rport_fast_io_fail_timedout() - fast I/O failure timeout handler
@@ -567,7 +539,6 @@ int srp_reconnect_rport(struct srp_rport *rport) 
	if (res)

		goto out;

	scsi_target_block(&shost->shost_gendev);

	srp_wait_for_queuecommand(shost);

	res = rport->state != SRP_RPORT_LOST ? i->f->reconnect(rport) : -ENODEV;

	pr_debug("%s (state %d): transport.reconnect() returned %d\n",

		 dev_name(&shost->shost_gendev), rport->state, res);

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