[SCSI] add global timeout to the scsi mid-layer

There are certain rogue devices (and the aic7xxx driver) that return
BUSY or QUEUE_FULL forever.  This code will apply a global timeout (of
the total number of retries times the per command timer) to a given
command.  If it is exceeded, the command is completed regardless of its
state.

The patch also removes the unused field in the command: timeout and
timeout_total.

This solves the problem of detecting an endless loop in the mid-layer
because of BUSY/QUEUE_FULL bouncing, but will not recover the device.
In the aic7xxx case, the driver can be recovered by sending a bus reset,
so possibly this should be tied into the error handler?

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index d1aa95d45a70..4befbc275f94 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -268,6 +268,7 @@ struct scsi_cmnd *scsi_get_command(struct scsi_device *dev, int gfp_mask)
         } else
                 put_device(&dev->sdev_gendev);
 
+        cmd->jiffies_at_alloc = jiffies;
         return cmd;
 }                               
 EXPORT_SYMBOL(scsi_get_command);
@@ -798,9 +799,23 @@ static void scsi_softirq(struct softirq_action *h)
         while (!list_empty(&local_q)) {
                 struct scsi_cmnd *cmd = list_entry(local_q.next,
                                                    struct scsi_cmnd, eh_entry);
+                /* The longest time any command should be outstanding is the
+                 * per command timeout multiplied by the number of retries.
+                 *
+                 * For a typical command, this is 2.5 minutes */
+                unsigned long wait_for 
+                        = cmd->allowed * cmd->timeout_per_command;
                 list_del_init(&cmd->eh_entry);
 
                 disposition = scsi_decide_disposition(cmd);
+                if (disposition != SUCCESS &&
+                    time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
+                        dev_printk(KERN_ERR, &cmd->device->sdev_gendev, 
+                                   "timing out command, waited %ds\n",
+                                   wait_for/HZ);
+                        disposition = SUCCESS;
+                }
+                        
                 scsi_log_completion(cmd, disposition);
                 switch (disposition) {
                 case SUCCESS: