Several SCSI transport and LLD drivers surround code that does not
tolerate concurrent calls of .queuecommand() with scsi_target_block() /
scsi_target_unblock(). These last two functions use
blk_mq_quiesce_queue() / blk_mq_unquiesce_queue() for scsi-mq request
queues to prevent concurrent .queuecommand() calls. However, that is
not sufficient to prevent .queuecommand() calls from scsi_send_eh_cmnd().
Hence surround the .queuecommand() call from the SCSI error handler with
code that avoids that .queuecommand() gets called in the blocked state.
Note: converting the .queuecommand() call in scsi_send_eh_cmnd() into
code that calls blk_get_request() + blk_execute_rq() is not an option
since scsi_send_eh_cmnd() must be able to make forward progress even
if all requests have been allocated.
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
drivers/scsi/scsi_error.c | 26 ++++++++++++++++++++++++--
drivers/scsi/scsi_lib.c | 4 ----
2 files changed, 24 insertions(+), 6 deletions(-)
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 8e9680572b9f..d516dd1b824d 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1054,7 +1054,7 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
struct scsi_device *sdev = scmd->device;
struct Scsi_Host *shost = sdev->host;
DECLARE_COMPLETION_ONSTACK(done);
- unsigned long timeleft = timeout;
+ unsigned long timeleft = timeout, delay;
struct scsi_eh_save ses;
const unsigned long stall_for = msecs_to_jiffies(100);
int rtn;
@@ -1065,7 +1065,29 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
scsi_log_send(scmd);
scmd->scsi_done = scsi_eh_done;
- rtn = shost->hostt->queuecommand(shost, scmd);
+
+ /*
+ * Lock sdev->state_mutex to avoid that scsi_device_quiesce() can
+ * change the SCSI device state after we have examined it and before
+ * .queuecommand() is called.
+ */
+ mutex_lock(&sdev->state_mutex);
+ while (sdev->sdev_state == SDEV_BLOCK && timeleft > 0) {
+ mutex_unlock(&sdev->state_mutex);
+ SCSI_LOG_ERROR_RECOVERY(5, sdev_printk(KERN_DEBUG, sdev,
+ "%s: state %d <> %d\n", __func__, sdev->sdev_state,
+ SDEV_BLOCK));
+ delay = min(timeleft, stall_for);
+ timeleft -= delay;
+ msleep(jiffies_to_msecs(delay));
+ mutex_lock(&sdev->state_mutex);
+ }
+ if (sdev->sdev_state != SDEV_BLOCK)
+ rtn = shost->hostt->queuecommand(shost, scmd);
+ else
+ rtn = SCSI_MLQUEUE_DEVICE_BUSY;
+ mutex_unlock(&sdev->state_mutex);
+
if (rtn) {
if (timeleft > stall_for) {
scsi_eh_restore_cmnd(scmd, &ses);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index b4a63e4fcf73..ec5b4b5bc011 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2632,10 +2632,6 @@ EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
* 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)
{
--
2.22.0.rc3
