[PATCH] sbp2: fix deadlocks and delays on device removal/rmmod

Fixes for deadlocks of the ieee1394 and scsi subsystems and long delays in
futile error recovery attempts when SBP-2 devices are removed or drivers are
unloaded.

 - Complete commands quickly with DID_NO_CONNECT if the 1394 node is gone or if
   the 1394 low-level driver was unloaded.
 - Skip unnecessary work in the eh_abort_handler and eh_device_reset_handler if
   the node or 1394 low-level driver is gone.
 - Let scsi's high-level shut down gracefully when sbp2 is being unloaded or
   detached from the 1394 unit. A call to scsi_remove_device is added for this
   purpose, which requires us to store a scsi_device pointer.
 - scsi_device pointer is obtained from slave_alloc hook and cleared by
   slave_destroy. This avoids usage of the pointer after the scsi device was
   deleted e.g. by the user via scsi_mod's sysfs interface.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Jody McIntyre <scjody@steamballoon.com>
Cc: Ben Collins <bcollins@debian.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 58 insertions, 38 deletions

diff --git a/drivers/ieee1394/sbp2.c b/drivers/ieee1394/sbp2.c
index de88218ef7cc..5d86b03979ec 100644
--- a/drivers/ieee1394/sbp2.c
+++ b/drivers/ieee1394/sbp2.c
@@ -596,6 +596,14 @@ static void sbp2util_mark_command_completed(struct scsi_id_instance_data *scsi_i
         spin_unlock_irqrestore(&scsi_id->sbp2_command_orb_lock, flags);
 }
 
+/*
+ * Is scsi_id valid? Is the 1394 node still present?
+ */
+static inline int sbp2util_node_is_available(struct scsi_id_instance_data *scsi_id)
+{
+        return scsi_id && scsi_id->ne && !scsi_id->ne->in_limbo;
+}
+
 
 
 /*********************************************
@@ -631,11 +639,23 @@ static int sbp2_remove(struct device *dev)
 {
         struct unit_directory *ud;
         struct scsi_id_instance_data *scsi_id;
+        struct scsi_device *sdev;
 
         SBP2_DEBUG("sbp2_remove");
 
         ud = container_of(dev, struct unit_directory, device);
         scsi_id = ud->device.driver_data;
+        if (!scsi_id)
+                return 0;
+
+        /* Trigger shutdown functions in scsi's highlevel. */
+        if (scsi_id->scsi_host)
+                scsi_unblock_requests(scsi_id->scsi_host);
+        sdev = scsi_id->sdev;
+        if (sdev) {
+                scsi_id->sdev = NULL;
+                scsi_remove_device(sdev);
+        }
 
         sbp2_logout_device(scsi_id);
         sbp2_remove_device(scsi_id);
@@ -2473,37 +2493,26 @@ static int sbp2scsi_queuecommand(struct scsi_cmnd *SCpnt,
         struct scsi_id_instance_data *scsi_id =
                 (struct scsi_id_instance_data *)SCpnt->device->host->hostdata[0];
         struct sbp2scsi_host_info *hi;
+        int result = DID_NO_CONNECT << 16;
 
         SBP2_DEBUG("sbp2scsi_queuecommand");
 
-        /*
-         * If scsi_id is null, it means there is no device in this slot,
-         * so we should return selection timeout.
-         */
-        if (!scsi_id) {
-                SCpnt->result = DID_NO_CONNECT << 16;
-                done (SCpnt);
-                return 0;
-        }
+        if (!sbp2util_node_is_available(scsi_id))
+                goto done;
 
         hi = scsi_id->hi;
 
         if (!hi) {
                 SBP2_ERR("sbp2scsi_host_info is NULL - this is bad!");
-                SCpnt->result = DID_NO_CONNECT << 16;
-                done (SCpnt);
-                return(0);
+                goto done;
         }
 
         /*
          * Until we handle multiple luns, just return selection time-out
          * to any IO directed at non-zero LUNs
          */
-        if (SCpnt->device->lun) {
-                SCpnt->result = DID_NO_CONNECT << 16;
-                done (SCpnt);
-                return(0);
-        }
+        if (SCpnt->device->lun)
+                goto done;
 
         /*
          * Check for request sense command, and handle it here
@@ -2514,7 +2523,7 @@ static int sbp2scsi_queuecommand(struct scsi_cmnd *SCpnt,
                 memcpy(SCpnt->request_buffer, SCpnt->sense_buffer, SCpnt->request_bufflen);
                 memset(SCpnt->sense_buffer, 0, sizeof(SCpnt->sense_buffer));
                 sbp2scsi_complete_command(scsi_id, SBP2_SCSI_STATUS_GOOD, SCpnt, done);
-                return(0);
+                return 0;
         }
 
         /*
@@ -2522,9 +2531,8 @@ static int sbp2scsi_queuecommand(struct scsi_cmnd *SCpnt,
          */
         if (!hpsb_node_entry_valid(scsi_id->ne)) {
                 SBP2_ERR("Bus reset in progress - rejecting command");
-                SCpnt->result = DID_BUS_BUSY << 16;
-                done (SCpnt);
-                return(0);
+                result = DID_BUS_BUSY << 16;
+                goto done;
         }
 
         /*
@@ -2535,8 +2543,12 @@ static int sbp2scsi_queuecommand(struct scsi_cmnd *SCpnt,
                 sbp2scsi_complete_command(scsi_id, SBP2_SCSI_STATUS_SELECTION_TIMEOUT,
                                           SCpnt, done);
         }
+        return 0;
 
-        return(0);
+done:
+        SCpnt->result = result;
+        done(SCpnt);
+        return 0;
 }
 
 /*
@@ -2683,14 +2695,27 @@ static void sbp2scsi_complete_command(struct scsi_id_instance_data *scsi_id,
 }
 
 
-static int sbp2scsi_slave_configure (struct scsi_device *sdev)
+static int sbp2scsi_slave_alloc(struct scsi_device *sdev)
 {
-        blk_queue_dma_alignment(sdev->request_queue, (512 - 1));
+        ((struct scsi_id_instance_data *)sdev->host->hostdata[0])->sdev = sdev;
+        return 0;
+}
+
 
+static int sbp2scsi_slave_configure(struct scsi_device *sdev)
+{
+        blk_queue_dma_alignment(sdev->request_queue, (512 - 1));
         return 0;
 }
 
 
+static void sbp2scsi_slave_destroy(struct scsi_device *sdev)
+{
+        ((struct scsi_id_instance_data *)sdev->host->hostdata[0])->sdev = NULL;
+        return;
+}
+
+
 /*
  * Called by scsi stack when something has really gone wrong.  Usually
  * called when a command has timed-out for some reason.
@@ -2705,7 +2730,7 @@ static int sbp2scsi_abort(struct scsi_cmnd *SCpnt)
         SBP2_ERR("aborting sbp2 command");
         scsi_print_command(SCpnt);
 
-        if (scsi_id) {
+        if (sbp2util_node_is_available(scsi_id)) {
 
                 /*
                  * Right now, just return any matching command structures
@@ -2742,31 +2767,24 @@ static int sbp2scsi_abort(struct scsi_cmnd *SCpnt)
 /*
  * Called by scsi stack when something has really gone wrong.
  */
-static int __sbp2scsi_reset(struct scsi_cmnd *SCpnt)
+static int sbp2scsi_reset(struct scsi_cmnd *SCpnt)
 {
         struct scsi_id_instance_data *scsi_id =
                 (struct scsi_id_instance_data *)SCpnt->device->host->hostdata[0];
+        unsigned long flags;
 
         SBP2_ERR("reset requested");
 
-        if (scsi_id) {
+        spin_lock_irqsave(SCpnt->device->host->host_lock, flags);
+
+        if (sbp2util_node_is_available(scsi_id)) {
                 SBP2_ERR("Generating sbp2 fetch agent reset");
                 sbp2_agent_reset(scsi_id, 0);
         }
 
-        return(SUCCESS);
-}
-
-static int sbp2scsi_reset(struct scsi_cmnd *SCpnt)
-{
-        unsigned long flags;
-        int rc;
-
-        spin_lock_irqsave(SCpnt->device->host->host_lock, flags);
-        rc = __sbp2scsi_reset(SCpnt);
         spin_unlock_irqrestore(SCpnt->device->host->host_lock, flags);
 
-        return rc;
+        return SUCCESS;
 }
 
 static const char *sbp2scsi_info (struct Scsi_Host *host)
@@ -2817,7 +2835,9 @@ static struct scsi_host_template scsi_driver_template = {
         .eh_device_reset_handler =      sbp2scsi_reset,
         .eh_bus_reset_handler =         sbp2scsi_reset,
         .eh_host_reset_handler =        sbp2scsi_reset,
+        .slave_alloc =                  sbp2scsi_slave_alloc,
         .slave_configure =              sbp2scsi_slave_configure,
+        .slave_destroy =                sbp2scsi_slave_destroy,
         .this_id =                      -1,
         .sg_tablesize =                 SG_ALL,
         .use_clustering =               ENABLE_CLUSTERING,