1 files changed, 122 insertions, 4 deletions

diff --git a/drivers/firewire/fw-sbp2.c b/drivers/firewire/fw-sbp2.c
index 6d10934c58f..ea4811c4551 100644
--- a/drivers/firewire/fw-sbp2.c
+++ b/drivers/firewire/fw-sbp2.c
@@ -139,6 +139,7 @@ struct sbp2_logical_unit {
         int generation;
         int retries;
         struct delayed_work work;
+        bool blocked;
 };
 
 /*
@@ -157,6 +158,9 @@ struct sbp2_target {
         int address_high;
         unsigned int workarounds;
         unsigned int mgt_orb_timeout;
+
+        int dont_block; /* counter for each logical unit */
+        int blocked;    /* ditto */
 };
 
 /*
@@ -646,6 +650,107 @@ static void sbp2_agent_reset_no_wait(struct sbp2_logical_unit *lu)
                         &z, sizeof(z), complete_agent_reset_write_no_wait, t);
 }
 
+static void sbp2_set_generation(struct sbp2_logical_unit *lu, int generation)
+{
+        struct fw_card *card = fw_device(lu->tgt->unit->device.parent)->card;
+        unsigned long flags;
+
+        /* serialize with comparisons of lu->generation and card->generation */
+        spin_lock_irqsave(&card->lock, flags);
+        lu->generation = generation;
+        spin_unlock_irqrestore(&card->lock, flags);
+}
+
+static inline void sbp2_allow_block(struct sbp2_logical_unit *lu)
+{
+        /*
+         * We may access dont_block without taking card->lock here:
+         * All callers of sbp2_allow_block() and all callers of sbp2_unblock()
+         * are currently serialized against each other.
+         * And a wrong result in sbp2_conditionally_block()'s access of
+         * dont_block is rather harmless, it simply misses its first chance.
+         */
+        --lu->tgt->dont_block;
+}
+
+/*
+ * Blocks lu->tgt if all of the following conditions are met:
+ *   - Login, INQUIRY, and high-level SCSI setup of all of the target's
+ *     logical units have been finished (indicated by dont_block == 0).
+ *   - lu->generation is stale.
+ *
+ * Note, scsi_block_requests() must be called while holding card->lock,
+ * otherwise it might foil sbp2_[conditionally_]unblock()'s attempt to
+ * unblock the target.
+ */
+static void sbp2_conditionally_block(struct sbp2_logical_unit *lu)
+{
+        struct sbp2_target *tgt = lu->tgt;
+        struct fw_card *card = fw_device(tgt->unit->device.parent)->card;
+        struct Scsi_Host *shost =
+                container_of((void *)tgt, struct Scsi_Host, hostdata[0]);
+        unsigned long flags;
+
+        spin_lock_irqsave(&card->lock, flags);
+        if (!tgt->dont_block && !lu->blocked &&
+            lu->generation != card->generation) {
+                lu->blocked = true;
+                if (++tgt->blocked == 1) {
+                        scsi_block_requests(shost);
+                        fw_notify("blocked %s\n", lu->tgt->bus_id);
+                }
+        }
+        spin_unlock_irqrestore(&card->lock, flags);
+}
+
+/*
+ * Unblocks lu->tgt as soon as all its logical units can be unblocked.
+ * Note, it is harmless to run scsi_unblock_requests() outside the
+ * card->lock protected section.  On the other hand, running it inside
+ * the section might clash with shost->host_lock.
+ */
+static void sbp2_conditionally_unblock(struct sbp2_logical_unit *lu)
+{
+        struct sbp2_target *tgt = lu->tgt;
+        struct fw_card *card = fw_device(tgt->unit->device.parent)->card;
+        struct Scsi_Host *shost =
+                container_of((void *)tgt, struct Scsi_Host, hostdata[0]);
+        unsigned long flags;
+        bool unblock = false;
+
+        spin_lock_irqsave(&card->lock, flags);
+        if (lu->blocked && lu->generation == card->generation) {
+                lu->blocked = false;
+                unblock = --tgt->blocked == 0;
+        }
+        spin_unlock_irqrestore(&card->lock, flags);
+
+        if (unblock) {
+                scsi_unblock_requests(shost);
+                fw_notify("unblocked %s\n", lu->tgt->bus_id);
+        }
+}
+
+/*
+ * Prevents future blocking of tgt and unblocks it.
+ * Note, it is harmless to run scsi_unblock_requests() outside the
+ * card->lock protected section.  On the other hand, running it inside
+ * the section might clash with shost->host_lock.
+ */
+static void sbp2_unblock(struct sbp2_target *tgt)
+{
+        struct fw_card *card = fw_device(tgt->unit->device.parent)->card;
+        struct Scsi_Host *shost =
+                container_of((void *)tgt, struct Scsi_Host, hostdata[0]);
+        unsigned long flags;
+
+        spin_lock_irqsave(&card->lock, flags);
+        ++tgt->dont_block;
+        spin_unlock_irqrestore(&card->lock, flags);
+
+        scsi_unblock_requests(shost);
+}
+
 static void sbp2_release_target(struct kref *kref)
 {
         struct sbp2_target *tgt = container_of(kref, struct sbp2_target, kref);
@@ -653,6 +758,9 @@ static void sbp2_release_target(struct kref *kref)
         struct Scsi_Host *shost =
                 container_of((void *)tgt, struct Scsi_Host, hostdata[0]);
 
+        /* prevent deadlocks */
+        sbp2_unblock(tgt);
+
         list_for_each_entry_safe(lu, next, &tgt->lu_list, link) {
                 if (lu->sdev)
                         scsi_remove_device(lu->sdev);
@@ -717,17 +825,20 @@ static void sbp2_login(struct work_struct *work)
 
         if (sbp2_send_management_orb(lu, node_id, generation,
                                 SBP2_LOGIN_REQUEST, lu->lun, &response) < 0) {
-                if (lu->retries++ < 5)
+                if (lu->retries++ < 5) {
                         sbp2_queue_work(lu, DIV_ROUND_UP(HZ, 5));
-                else
+                } else {
                         fw_error("%s: failed to login to LUN %04x\n",
                                  tgt->bus_id, lu->lun);
+                        /* Let any waiting I/O fail from now on. */
+                        sbp2_unblock(lu->tgt);
+                }
                 goto out;
         }
 
-        lu->generation    = generation;
         tgt->node_id      = node_id;
         tgt->address_high = local_node_id << 16;
+        sbp2_set_generation(lu, generation);
 
         /* Get command block agent offset and login id. */
         lu->command_block_agent_address =
@@ -749,6 +860,7 @@ static void sbp2_login(struct work_struct *work)
         /* This was a re-login. */
         if (lu->sdev) {
                 sbp2_cancel_orbs(lu);
+                sbp2_conditionally_unblock(lu);
                 goto out;
         }
 
@@ -785,6 +897,7 @@ static void sbp2_login(struct work_struct *work)
 
         /* No error during __scsi_add_device() */
         lu->sdev = sdev;
+        sbp2_allow_block(lu);
         goto out;
 
  out_logout_login:
@@ -825,6 +938,8 @@ static int sbp2_add_logical_unit(struct sbp2_target *tgt, int lun_entry)
         lu->sdev = NULL;
         lu->lun  = lun_entry & 0xffff;
         lu->retries = 0;
+        lu->blocked = false;
+        ++tgt->dont_block;
         INIT_LIST_HEAD(&lu->orb_list);
         INIT_DELAYED_WORK(&lu->work, sbp2_login);
 
@@ -1041,15 +1156,16 @@ static void sbp2_reconnect(struct work_struct *work)
                 goto out;
         }
 
-        lu->generation    = generation;
         tgt->node_id      = node_id;
         tgt->address_high = local_node_id << 16;
+        sbp2_set_generation(lu, generation);
 
         fw_notify("%s: reconnected to LUN %04x (%d retries)\n",
                   tgt->bus_id, lu->lun, lu->retries);
 
         sbp2_agent_reset(lu);
         sbp2_cancel_orbs(lu);
+        sbp2_conditionally_unblock(lu);
  out:
         sbp2_target_put(tgt);
 }
@@ -1066,6 +1182,7 @@ static void sbp2_update(struct fw_unit *unit)
          * Iteration over tgt->lu_list is therefore safe here.
          */
         list_for_each_entry(lu, &tgt->lu_list, link) {
+                sbp2_conditionally_block(lu);
                 lu->retries = 0;
                 sbp2_queue_work(lu, 0);
         }
@@ -1169,6 +1286,7 @@ complete_command_orb(struct sbp2_orb *base_orb, struct sbp2_status *status)
                  * or when sending the write (less likely).
                  */
                 result = DID_BUS_BUSY << 16;
+                sbp2_conditionally_block(orb->lu);
         }
 
         dma_unmap_single(device->card->device, orb->base.request_bus,