[SCSI] limit state transitions in scsi_internal_device_unblock

scsi timeout on two or more devices may cause extremely long execution
time for user applications because SDEV_OFFLINE state is changed to
SDEV_RUNNING state during scsi error recovery procedures triggered by
a bus reset or a host reset of scsi LLD, and scsi timeout can happens
on the same devices many times.

This happens because scsi_internal_device_unblock() changes device's
state to SDEV_RUNNING even if a device in other states than SDEV_BLOCK,
while the following two transitions are required in this function.

  SDEV_BLOCK -> SDEV_RUNNING
  SDEV_CREATED_BLOCK -> SDEV_CREATED

Otherwise, it returns -EINVAL.

Signed-off-by: Takahiro Yasui <tyasui@redhat.com>
[matthew@wil.cx: supplied rewritten base for patch]
Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 6 insertions, 8 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index bb218c8b6e98..27dbf2e8e34a 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2441,20 +2441,18 @@ int
 scsi_internal_device_unblock(struct scsi_device *sdev)
 {
         struct request_queue *q = sdev->request_queue; 
-        int err;
         unsigned long flags;
         
         /* 
          * Try to transition the scsi device to SDEV_RUNNING
          * and goose the device queue if successful.  
          */
-        err = scsi_device_set_state(sdev, SDEV_RUNNING);
-        if (err) {
-                err = scsi_device_set_state(sdev, SDEV_CREATED);
-
-                if (err)
-                        return err;
-        }
+        if (sdev->sdev_state == SDEV_BLOCK)
+                sdev->sdev_state = SDEV_RUNNING;
+        else if (sdev->sdev_state == SDEV_CREATED_BLOCK)
+                sdev->sdev_state = SDEV_CREATED;
+        else
+                return -EINVAL;
 
         spin_lock_irqsave(q->queue_lock, flags);
         blk_start_queue(q);