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 quiesced state.
Notes:
- 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 are allocated.
- Converting the .queuecommand() call in scsi_send_eh_cmnd() into a
blk_execute_rq() or blk_mq_requeue_request() call is not an option either
because that would require to change every individual function in the I/O
path. Each function in the I/O path would have to be modified such that it
handles requests received from the block layer core and request received
from the SCSI EH differently. Since struct scsi_cmnd is not initialized by
the block layer for filesystem requests, it is not possible to determine
in scsi_queue_rq() whether or not a request has been submitted by the
SCSI EH without modifying the block layer.
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
---
Changes compared to v1:
- As requested by James, removed the wait queue again that was added to the
SCSI device structure.
drivers/scsi/scsi_error.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 946039117bf4..71d7d2b893ab 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1039,7 +1039,7 @@ 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;
@@ -1050,7 +1050,22 @@ 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);
+ mutex_lock(&sdev->state_mutex);
+ while (sdev->sdev_state == SDEV_QUIESCE && 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_QUIESCE));
+ delay = min(timeleft, stall_for);
+ timeleft -= delay;
+ msleep(jiffies_to_msecs(delay));
+ mutex_lock(&sdev->state_mutex);
+ }
+ if (sdev->sdev_state != SDEV_QUIESCE)
+ 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);
--
2.16.2
