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>
---
drivers/scsi/scsi_error.c | 13 +++++++++++++
drivers/scsi/scsi_lib.c | 2 ++
drivers/scsi/scsi_scan.c | 1 +
include/scsi/scsi_device.h | 1 +
4 files changed, 17 insertions(+)
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 946039117bf4..cfc805851a2a 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1042,6 +1042,7 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
unsigned long timeleft = timeout;
struct scsi_eh_save ses;
const unsigned long stall_for = msecs_to_jiffies(100);
+ DEFINE_WAIT(wait);
int rtn;
retry:
@@ -1050,7 +1051,19 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
scsi_log_send(scmd);
scmd->scsi_done = scsi_eh_done;
+ mutex_lock(&sdev->state_mutex);
+ while (sdev->sdev_state == SDEV_QUIESCE) {
+ prepare_to_wait(&sdev->state_wq, &wait, TASK_INTERRUPTIBLE);
+ 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));
+ schedule();
+ mutex_lock(&sdev->state_mutex);
+ }
+ finish_wait(&sdev->state_wq, &wait);
rtn = shost->hostt->queuecommand(shost, scmd);
+ 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 1d83f29aee74..99741858b6da 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2757,6 +2757,7 @@ scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
}
sdev->sdev_state = state;
+ wake_up_all(&sdev->state_wq);
return 0;
illegal:
@@ -3216,6 +3217,7 @@ int scsi_internal_device_unblock_nowait(struct scsi_device *sdev,
default:
return -EINVAL;
}
+ wake_up_all(&sdev->state_wq);
scsi_start_queue(sdev);
return 0;
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 0880d975eed3..32439ca61c18 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -232,6 +232,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
sdev->id = starget->id;
sdev->lun = lun;
sdev->channel = starget->channel;
+ init_waitqueue_head(&sdev->state_wq);
mutex_init(&sdev->state_mutex);
sdev->sdev_state = SDEV_CREATED;
INIT_LIST_HEAD(&sdev->siblings);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 7ae177c8e399..eb9063202036 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -222,6 +222,7 @@ struct scsi_device {
void *handler_data;
unsigned char access_state;
+ struct wait_queue_head state_wq;
struct mutex state_mutex;
enum scsi_device_state sdev_state;
struct task_struct *quiesced_by;
--
2.16.2
