[PATCH] USB: ub 00 implement retries and resets

Implement command retries and resets in ub. It is advantageous for users
to know if their devices are getting bad. However, failing every I/O
is not practical if you have a external USB enclosure with a hard drive.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 287 insertions, 117 deletions

diff --git a/drivers/block/ub.c b/drivers/block/ub.c
index c7a28f5be42f..ba05e31709d5 100644
--- a/drivers/block/ub.c
+++ b/drivers/block/ub.c
@@ -9,7 +9,6 @@
  *
  * TODO (sorted by decreasing priority)
  *  -- Kill first_open (Al Viro fixed the block layer now)
- *  -- Do resets with usb_device_reset (needs a thread context, use khubd)
  *  -- set readonly flag for CDs, set removable flag for CF readers
  *  -- do inquiry and verify we got a disk and not a tape (for LUN mismatch)
  *  -- special case some senses, e.g. 3a/0 -> no media present, reduce retries
@@ -236,6 +235,13 @@ struct ub_scsi_cmd {
         void *back;
 };
 
+struct ub_request {
+        struct request *rq;
+        unsigned int current_try;
+        unsigned int nsg;               /* sgv[nsg] */
+        struct scatterlist sgv[UB_MAX_REQ_SG];
+};
+
 /*
  */
 struct ub_capacity {
@@ -331,6 +337,8 @@ struct ub_lun {
         int readonly;
         int first_open;                 /* Kludge. See ub_bd_open. */
 
+        struct ub_request urq;
+
         /* Use Ingo's mempool if or when we have more than one command. */
         /*
          * Currently we never need more than one command for the whole device.
@@ -351,6 +359,7 @@ struct ub_dev {
         atomic_t poison;                /* The USB device is disconnected */
         int openc;                      /* protected by ub_lock! */
                                         /* kref is too implicit for our taste */
+        int reset;                      /* Reset is running */
         unsigned int tagcnt;
         char name[12];
         struct usb_device *dev;
@@ -378,6 +387,9 @@ struct ub_dev {
         struct bulk_cs_wrap work_bcs;
         struct usb_ctrlrequest work_cr;
 
+        struct work_struct reset_work;
+        wait_queue_head_t reset_wait;
+
         int sg_stat[6];
         struct ub_scsi_trace tr;
 };
@@ -386,12 +398,14 @@ struct ub_dev {
  */
 static void ub_cleanup(struct ub_dev *sc);
 static int ub_request_fn_1(struct ub_lun *lun, struct request *rq);
-static int ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
-    struct ub_scsi_cmd *cmd, struct request *rq);
-static int ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
-    struct ub_scsi_cmd *cmd, struct request *rq);
+static void ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
+    struct ub_scsi_cmd *cmd, struct ub_request *urq);
+static void ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
+    struct ub_scsi_cmd *cmd, struct ub_request *urq);
 static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
 static void ub_end_rq(struct request *rq, int uptodate);
+static int ub_rw_cmd_retry(struct ub_dev *sc, struct ub_lun *lun,
+    struct ub_request *urq, struct ub_scsi_cmd *cmd);
 static int ub_submit_scsi(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
 static void ub_urb_complete(struct urb *urb, struct pt_regs *pt);
 static void ub_scsi_action(unsigned long _dev);
@@ -406,6 +420,8 @@ static void ub_state_sense(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
 static int ub_submit_clear_stall(struct ub_dev *sc, struct ub_scsi_cmd *cmd,
     int stalled_pipe);
 static void ub_top_sense_done(struct ub_dev *sc, struct ub_scsi_cmd *scmd);
+static void ub_reset_enter(struct ub_dev *sc);
+static void ub_reset_task(void *arg);
 static int ub_sync_tur(struct ub_dev *sc, struct ub_lun *lun);
 static int ub_sync_read_cap(struct ub_dev *sc, struct ub_lun *lun,
     struct ub_capacity *ret);
@@ -518,6 +534,9 @@ static ssize_t ub_diag_show(struct device *dev, struct device_attribute *attr,
         spin_lock_irqsave(&sc->lock, flags);
 
         cnt += sprintf(page + cnt,
+            "poison %d reset %d\n",
+            atomic_read(&sc->poison), sc->reset);
+        cnt += sprintf(page + cnt,
             "qlen %d qmax %d\n",
             sc->cmd_queue.qlen, sc->cmd_queue.qmax);
         cnt += sprintf(page + cnt,
@@ -766,7 +785,8 @@ static int ub_request_fn_1(struct ub_lun *lun, struct request *rq)
 {
         struct ub_dev *sc = lun->udev;
         struct ub_scsi_cmd *cmd;
-        int rc;
+        struct ub_request *urq;
+        int n_elem;
 
         if (atomic_read(&sc->poison) || lun->changed) {
                 blkdev_dequeue_request(rq);
@@ -774,65 +794,70 @@ static int ub_request_fn_1(struct ub_lun *lun, struct request *rq)
                 return 0;
         }
 
+        if (lun->urq.rq != NULL)
+                return -1;
         if ((cmd = ub_get_cmd(lun)) == NULL)
                 return -1;
         memset(cmd, 0, sizeof(struct ub_scsi_cmd));
 
         blkdev_dequeue_request(rq);
+
+        urq = &lun->urq;
+        memset(urq, 0, sizeof(struct ub_request));
+        urq->rq = rq;
+
+        /*
+         * get scatterlist from block layer
+         */
+        n_elem = blk_rq_map_sg(lun->disk->queue, rq, &urq->sgv[0]);
+        if (n_elem < 0) {
+                printk(KERN_INFO "%s: failed request map (%d)\n",
+                    lun->name, n_elem); /* P3 */
+                goto drop;
+        }
+        if (n_elem > UB_MAX_REQ_SG) {   /* Paranoia */
+                printk(KERN_WARNING "%s: request with %d segments\n",
+                    lun->name, n_elem);
+                goto drop;
+        }
+        urq->nsg = n_elem;
+        sc->sg_stat[n_elem < 5 ? n_elem : 5]++;
+
         if (blk_pc_request(rq)) {
-                rc = ub_cmd_build_packet(sc, lun, cmd, rq);
+                ub_cmd_build_packet(sc, lun, cmd, urq);
         } else {
-                rc = ub_cmd_build_block(sc, lun, cmd, rq);
-        }
-        if (rc != 0) {
-                ub_put_cmd(lun, cmd);
-                ub_end_rq(rq, 0);
-                return 0;
+                ub_cmd_build_block(sc, lun, cmd, urq);
         }
         cmd->state = UB_CMDST_INIT;
         cmd->lun = lun;
         cmd->done = ub_rw_cmd_done;
-        cmd->back = rq;
+        cmd->back = urq;
 
         cmd->tag = sc->tagcnt++;
-        if (ub_submit_scsi(sc, cmd) != 0) {
-                ub_put_cmd(lun, cmd);
-                ub_end_rq(rq, 0);
-                return 0;
-        }
+        if (ub_submit_scsi(sc, cmd) != 0)
+                goto drop;
+
+        return 0;
 
+drop:
+        ub_put_cmd(lun, cmd);
+        ub_end_rq(rq, 0);
         return 0;
 }
 
-static int ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
-    struct ub_scsi_cmd *cmd, struct request *rq)
+static void ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
+    struct ub_scsi_cmd *cmd, struct ub_request *urq)
 {
-        int ub_dir;
-        int n_elem;
+        struct request *rq = urq->rq;
         unsigned int block, nblks;
 
         if (rq_data_dir(rq) == WRITE)
-                ub_dir = UB_DIR_WRITE;
+                cmd->dir = UB_DIR_WRITE;
         else
-                ub_dir = UB_DIR_READ;
-        cmd->dir = ub_dir;
+                cmd->dir = UB_DIR_READ;
 
-        /*
-         * get scatterlist from block layer
-         */
-        n_elem = blk_rq_map_sg(lun->disk->queue, rq, &cmd->sgv[0]);
-        if (n_elem <= 0) {
-                printk(KERN_INFO "%s: failed request map (%d)\n",
-                    sc->name, n_elem); /* P3 */
-                return -1;              /* request with no s/g entries? */
-        }
-        if (n_elem > UB_MAX_REQ_SG) {   /* Paranoia */
-                printk(KERN_WARNING "%s: request with %d segments\n",
-                    sc->name, n_elem);
-                return -1;
-        }
-        cmd->nsg = n_elem;
-        sc->sg_stat[n_elem < 5 ? n_elem : 5]++;
+        cmd->nsg = urq->nsg;
+        memcpy(cmd->sgv, urq->sgv, sizeof(struct scatterlist) * cmd->nsg);
 
         /*
          * build the command
@@ -843,7 +868,7 @@ static int ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
         block = rq->sector >> lun->capacity.bshift;
         nblks = rq->nr_sectors >> lun->capacity.bshift;
 
-        cmd->cdb[0] = (ub_dir == UB_DIR_READ)? READ_10: WRITE_10;
+        cmd->cdb[0] = (cmd->dir == UB_DIR_READ)? READ_10: WRITE_10;
         /* 10-byte uses 4 bytes of LBA: 2147483648KB, 2097152MB, 2048GB */
         cmd->cdb[2] = block >> 24;
         cmd->cdb[3] = block >> 16;
@@ -854,14 +879,12 @@ static int ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
         cmd->cdb_len = 10;
 
         cmd->len = rq->nr_sectors * 512;
-
-        return 0;
 }
 
-static int ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
-    struct ub_scsi_cmd *cmd, struct request *rq)
+static void ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
+    struct ub_scsi_cmd *cmd, struct ub_request *urq)
 {
-        int n_elem;
+        struct request *rq = urq->rq;
 
         if (rq->data_len == 0) {
                 cmd->dir = UB_DIR_NONE;
@@ -870,40 +893,26 @@ static int ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
                         cmd->dir = UB_DIR_WRITE;
                 else
                         cmd->dir = UB_DIR_READ;
-
         }
 
-        /*
-         * get scatterlist from block layer
-         */
-        n_elem = blk_rq_map_sg(lun->disk->queue, rq, &cmd->sgv[0]);
-        if (n_elem < 0) {
-                printk(KERN_INFO "%s: failed request map (%d)\n",
-                    sc->name, n_elem); /* P3 */
-                return -1;
-        }
-        if (n_elem > UB_MAX_REQ_SG) {   /* Paranoia */
-                printk(KERN_WARNING "%s: request with %d segments\n",
-                    sc->name, n_elem);
-                return -1;
-        }
-        cmd->nsg = n_elem;
-        sc->sg_stat[n_elem < 5 ? n_elem : 5]++;
+        cmd->nsg = urq->nsg;
+        memcpy(cmd->sgv, urq->sgv, sizeof(struct scatterlist) * cmd->nsg);
 
         memcpy(&cmd->cdb, rq->cmd, rq->cmd_len);
         cmd->cdb_len = rq->cmd_len;
 
         cmd->len = rq->data_len;
-
-        return 0;
 }
 
 static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
 {
-        struct request *rq = cmd->back;
         struct ub_lun *lun = cmd->lun;
+        struct ub_request *urq = cmd->back;
+        struct request *rq;
         int uptodate;
 
+        rq = urq->rq;
+
         if (cmd->error == 0) {
                 uptodate = 1;
 
@@ -924,9 +933,16 @@ static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                                 rq->errors = SAM_STAT_CHECK_CONDITION;
                         else
                                 rq->errors = DID_ERROR << 16;
+                } else {
+                        if (cmd->error == -EIO) {
+                                if (ub_rw_cmd_retry(sc, lun, urq, cmd) == 0)
+                                        return;
+                        }
                 }
         }
 
+        urq->rq = NULL;
+
         ub_put_cmd(lun, cmd);
         ub_end_rq(rq, uptodate);
         blk_start_queue(lun->disk->queue);
@@ -941,6 +957,41 @@ static void ub_end_rq(struct request *rq, int uptodate)
         end_that_request_last(rq);
 }
 
+static int ub_rw_cmd_retry(struct ub_dev *sc, struct ub_lun *lun,
+    struct ub_request *urq, struct ub_scsi_cmd *cmd)
+{
+
+        if (atomic_read(&sc->poison))
+                return -ENXIO;
+
+        ub_reset_enter(sc);
+
+        if (urq->current_try >= 3)
+                return -EIO;
+        urq->current_try++;
+        /* P3 */ printk("%s: dir %c len/act %d/%d "
+            "[sense %x %02x %02x] retry %d\n",
+            sc->name, UB_DIR_CHAR(cmd->dir), cmd->len, cmd->act_len,
+            cmd->key, cmd->asc, cmd->ascq, urq->current_try);
+
+        memset(cmd, 0, sizeof(struct ub_scsi_cmd));
+        ub_cmd_build_block(sc, lun, cmd, urq);
+
+        cmd->state = UB_CMDST_INIT;
+        cmd->lun = lun;
+        cmd->done = ub_rw_cmd_done;
+        cmd->back = urq;
+
+        cmd->tag = sc->tagcnt++;
+
+#if 0 /* Wasteful */
+        return ub_submit_scsi(sc, cmd);
+#else
+        ub_cmdq_add(sc, cmd);
+        return 0;
+#endif
+}
+
 /*
  * Submit a regular SCSI operation (not an auto-sense).
  *
@@ -1071,7 +1122,7 @@ static void ub_scsi_dispatch(struct ub_dev *sc)
         struct ub_scsi_cmd *cmd;
         int rc;
 
-        while ((cmd = ub_cmdq_peek(sc)) != NULL) {
+        while (!sc->reset && (cmd = ub_cmdq_peek(sc)) != NULL) {
                 if (cmd->state == UB_CMDST_DONE) {
                         ub_cmdq_pop(sc);
                         (*cmd->done)(sc, cmd);
@@ -1094,11 +1145,12 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
 {
         struct urb *urb = &sc->work_urb;
         struct bulk_cs_wrap *bcs;
+        int len;
         int rc;
 
         if (atomic_read(&sc->poison)) {
-                /* A little too simplistic, I feel... */
-                goto Bad_End;
+                ub_state_done(sc, cmd, -ENODEV);
+                return;
         }
 
         if (cmd->state == UB_CMDST_CLEAR) {
@@ -1106,7 +1158,6 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                         /*
                          * STALL while clearning STALL.
                          * The control pipe clears itself - nothing to do.
-                         * XXX Might try to reset the device here and retry.
                          */
                         printk(KERN_NOTICE "%s: stall on control pipe\n",
                             sc->name);
@@ -1125,11 +1176,6 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
 
         } else if (cmd->state == UB_CMDST_CLR2STS) {
                 if (urb->status == -EPIPE) {
-                        /*
-                         * STALL while clearning STALL.
-                         * The control pipe clears itself - nothing to do.
-                         * XXX Might try to reset the device here and retry.
-                         */
                         printk(KERN_NOTICE "%s: stall on control pipe\n",
                             sc->name);
                         goto Bad_End;
@@ -1147,11 +1193,6 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
 
         } else if (cmd->state == UB_CMDST_CLRRS) {
                 if (urb->status == -EPIPE) {
-                        /*
-                         * STALL while clearning STALL.
-                         * The control pipe clears itself - nothing to do.
-                         * XXX Might try to reset the device here and retry.
-                         */
                         printk(KERN_NOTICE "%s: stall on control pipe\n",
                             sc->name);
                         goto Bad_End;
@@ -1168,7 +1209,12 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                 ub_state_stat_counted(sc, cmd);
 
         } else if (cmd->state == UB_CMDST_CMD) {
-                if (urb->status == -EPIPE) {
+                switch (urb->status) {
+                case 0:
+                        break;
+                case -EOVERFLOW:
+                        goto Bad_End;
+                case -EPIPE:
                         rc = ub_submit_clear_stall(sc, cmd, sc->last_pipe);
                         if (rc != 0) {
                                 printk(KERN_NOTICE "%s: "
@@ -1178,17 +1224,20 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                                  * This is typically ENOMEM or some other such shit.
                                  * Retrying is pointless. Just do Bad End on it...
                                  */
-                                goto Bad_End;
+                                ub_state_done(sc, cmd, rc);
+                                return;
                         }
                         cmd->state = UB_CMDST_CLEAR;
                         ub_cmdtr_state(sc, cmd);
                         return;
-                }
-                if (urb->status != 0) {
+                case -ESHUTDOWN:        /* unplug */
+                case -EILSEQ:           /* unplug timeout on uhci */
+                        ub_state_done(sc, cmd, -ENODEV);
+                        return;
+                default:
                         goto Bad_End;
                 }
                 if (urb->actual_length != US_BULK_CB_WRAP_LEN) {
-                        /* XXX Must do reset here to unconfuse the device */
                         goto Bad_End;
                 }
 
@@ -1207,11 +1256,8 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                                 printk(KERN_NOTICE "%s: "
                                     "unable to submit clear (%d)\n",
                                     sc->name, rc);
-                                /*
-                                 * This is typically ENOMEM or some other such shit.
-                                 * Retrying is pointless. Just do Bad End on it...
-                                 */
-                                goto Bad_End;
+                                ub_state_done(sc, cmd, rc);
+                                return;
                         }
                         cmd->state = UB_CMDST_CLR2STS;
                         ub_cmdtr_state(sc, cmd);
@@ -1220,14 +1266,50 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                 if (urb->status == -EOVERFLOW) {
                         /*
                          * A babble? Failure, but we must transfer CSW now.
-                         * XXX This is going to end in perpetual babble. Reset.
                          */
                         cmd->error = -EOVERFLOW;        /* A cheap trick... */
                         ub_state_stat(sc, cmd);
                         return;
                 }
-                if (urb->status != 0)
-                        goto Bad_End;
+
+                if (cmd->dir == UB_DIR_WRITE) {
+                        /*
+                         * Do not continue writes in case of a failure.
+                         * Doing so would cause sectors to be mixed up,
+                         * which is worse than sectors lost.
+                         *
+                         * We must try to read the CSW, or many devices
+                         * get confused.
+                         */
+                        len = urb->actual_length;
+                        if (urb->status != 0 ||
+                            len != cmd->sgv[cmd->current_sg].length) {
+                                cmd->act_len += len;
+                                ub_cmdtr_act_len(sc, cmd);
+
+                                cmd->error = -EIO;
+                                ub_state_stat(sc, cmd);
+                                return;
+                        }
+
+                } else {
+                        /*
+                         * If an error occurs on read, we record it, and
+                         * continue to fetch data in order to avoid bubble.
+                         *
+                         * As a small shortcut, we stop if we detect that
+                         * a CSW mixed into data.
+                         */
+                        if (urb->status != 0)
+                                cmd->error = -EIO;
+
+                        len = urb->actual_length;
+                        if (urb->status != 0 ||
+                            len != cmd->sgv[cmd->current_sg].length) {
+                                if ((len & 0x1FF) == US_BULK_CS_WRAP_LEN)
+                                        goto Bad_End;
+                        }
+                }
 
                 cmd->act_len += urb->actual_length;
                 ub_cmdtr_act_len(sc, cmd);
@@ -1245,11 +1327,8 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                                 printk(KERN_NOTICE "%s: "
                                     "unable to submit clear (%d)\n",
                                     sc->name, rc);
-                                /*
-                                 * This is typically ENOMEM or some other such shit.
-                                 * Retrying is pointless. Just do Bad End on it...
-                                 */
-                                goto Bad_End;
+                                ub_state_done(sc, cmd, rc);
+                                return;
                         }
 
                         /*
@@ -1262,14 +1341,8 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                         ub_cmdtr_state(sc, cmd);
                         return;
                 }
-                if (urb->status == -EOVERFLOW) {
-                        /*
-                         * XXX We are screwed here. Retrying is pointless,
-                         * because the pipelined data will not get in until
-                         * we read with a big enough buffer. We must reset XXX.
-                         */
-                        goto Bad_End;
-                }
+
+                /* Catch everything, including -EOVERFLOW and other nasties. */
                 if (urb->status != 0)
                         goto Bad_End;
 
@@ -1315,15 +1388,15 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                         return;
                 }
 
-                rc = le32_to_cpu(bcs->Residue);
-                if (rc != cmd->len - cmd->act_len) {
+                len = le32_to_cpu(bcs->Residue);
+                if (len != cmd->len - cmd->act_len) {
                         /*
                          * It is all right to transfer less, the caller has
                          * to check. But it's not all right if the device
                          * counts disagree with our counts.
                          */
                         /* P3 */ printk("%s: resid %d len %d act %d\n",
-                            sc->name, rc, cmd->len, cmd->act_len);
+                            sc->name, len, cmd->len, cmd->act_len);
                         goto Bad_End;
                 }
 
@@ -1334,13 +1407,13 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                         ub_state_sense(sc, cmd);
                         return;
                 case US_BULK_STAT_PHASE:
-                        /* XXX We must reset the transport here */
                         /* P3 */ printk("%s: status PHASE\n", sc->name);
                         goto Bad_End;
                 default:
                         printk(KERN_INFO "%s: unknown CSW status 0x%x\n",
                             sc->name, bcs->Status);
-                        goto Bad_End;
+                        ub_state_done(sc, cmd, -EINVAL);
+                        return;
                 }
 
                 /* Not zeroing error to preserve a babble indicator */
@@ -1360,7 +1433,8 @@ static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
                 printk(KERN_WARNING "%s: "
                     "wrong command state %d\n",
                     sc->name, cmd->state);
-                goto Bad_End;
+                ub_state_done(sc, cmd, -EINVAL);
+                return;
         }
         return;
 
@@ -1608,6 +1682,93 @@ static void ub_top_sense_done(struct ub_dev *sc, struct ub_scsi_cmd *scmd)
 }
 
 /*
+ * Reset management
+ */
+
+static void ub_reset_enter(struct ub_dev *sc)
+{
+
+        if (sc->reset) {
+                /* This happens often on multi-LUN devices. */
+                return;
+        }
+        sc->reset = 1;
+
+#if 0 /* Not needed because the disconnect waits for us. */
+        unsigned long flags;
+        spin_lock_irqsave(&ub_lock, flags);
+        sc->openc++;
+        spin_unlock_irqrestore(&ub_lock, flags);
+#endif
+
+#if 0 /* We let them stop themselves. */
+        struct list_head *p;
+        struct ub_lun *lun;
+        list_for_each(p, &sc->luns) {
+                lun = list_entry(p, struct ub_lun, link);
+                blk_stop_queue(lun->disk->queue);
+        }
+#endif
+
+        schedule_work(&sc->reset_work);
+}
+
+static void ub_reset_task(void *arg)
+{
+        struct ub_dev *sc = arg;
+        unsigned long flags;
+        struct list_head *p;
+        struct ub_lun *lun;
+        int lkr, rc;
+
+        if (!sc->reset) {
+                printk(KERN_WARNING "%s: Running reset unrequested\n",
+                    sc->name);
+                return;
+        }
+
+        if (atomic_read(&sc->poison)) {
+                printk(KERN_NOTICE "%s: Not resetting disconnected device\n",
+                    sc->name); /* P3 This floods. Remove soon. XXX */
+        } else if (sc->dev->actconfig->desc.bNumInterfaces != 1) {
+                printk(KERN_NOTICE "%s: Not resetting multi-interface device\n",
+                    sc->name); /* P3 This floods. Remove soon. XXX */
+        } else {
+                if ((lkr = usb_lock_device_for_reset(sc->dev, sc->intf)) < 0) {
+                        printk(KERN_NOTICE
+                            "%s: usb_lock_device_for_reset failed (%d)\n",
+                            sc->name, lkr);
+                } else {
+                        rc = usb_reset_device(sc->dev);
+                        if (rc < 0) {
+                                printk(KERN_NOTICE "%s: "
+                                    "usb_lock_device_for_reset failed (%d)\n",
+                                    sc->name, rc);
+                        }
+
+                        if (lkr)
+                                usb_unlock_device(sc->dev);
+                }
+        }
+
+        /*
+         * In theory, no commands can be running while reset is active,
+         * so nobody can ask for another reset, and so we do not need any
+         * queues of resets or anything. We do need a spinlock though,
+         * to interact with block layer.
+         */
+        spin_lock_irqsave(&sc->lock, flags);
+        sc->reset = 0;
+        tasklet_schedule(&sc->tasklet);
+        list_for_each(p, &sc->luns) {
+                lun = list_entry(p, struct ub_lun, link);
+                blk_start_queue(lun->disk->queue);
+        }
+        wake_up(&sc->reset_wait);
+        spin_unlock_irqrestore(&sc->lock, flags);
+}
+
+/*
  * This is called from a process context.
  */
 static void ub_revalidate(struct ub_dev *sc, struct ub_lun *lun)
@@ -2142,7 +2303,7 @@ static int ub_get_pipes(struct ub_dev *sc, struct usb_device *dev,
         if (ep_in == NULL || ep_out == NULL) {
                 printk(KERN_NOTICE "%s: failed endpoint check\n",
                     sc->name);
-                return -EIO;
+                return -ENODEV;
         }
 
         /* Calculate and store the pipe values */
@@ -2180,6 +2341,8 @@ static int ub_probe(struct usb_interface *intf,
         usb_init_urb(&sc->work_urb);
         tasklet_init(&sc->tasklet, ub_scsi_action, (unsigned long)sc);
         atomic_set(&sc->poison, 0);
+        INIT_WORK(&sc->reset_work, ub_reset_task, sc);
+        init_waitqueue_head(&sc->reset_wait);
 
         init_timer(&sc->work_timer);
         sc->work_timer.data = (unsigned long) sc;
@@ -2200,7 +2363,8 @@ static int ub_probe(struct usb_interface *intf,
 
         /* XXX Verify that we can handle the device (from descriptors) */
 
-        ub_get_pipes(sc, sc->dev, intf);
+        if (ub_get_pipes(sc, sc->dev, intf) != 0)
+                goto err_dev_desc;
 
         if (device_create_file(&sc->intf->dev, &dev_attr_diag) != 0)
                 goto err_diag;
@@ -2271,6 +2435,7 @@ static int ub_probe(struct usb_interface *intf,
 
         /* device_remove_file(&sc->intf->dev, &dev_attr_diag); */
 err_diag:
+err_dev_desc:
         usb_set_intfdata(intf, NULL);
         // usb_put_intf(sc->intf);
         usb_put_dev(sc->dev);
@@ -2379,6 +2544,11 @@ static void ub_disconnect(struct usb_interface *intf)
         atomic_set(&sc->poison, 1);
 
         /*
+         * Wait for reset to end, if any.
+         */
+        wait_event(sc->reset_wait, !sc->reset);
+
+        /*
          * Blow away queued commands.
          *
          * Actually, this never works, because before we get here
@@ -2391,7 +2561,7 @@ static void ub_disconnect(struct usb_interface *intf)
         {
                 struct ub_scsi_cmd *cmd;
                 int cnt = 0;
-                while ((cmd = ub_cmdq_pop(sc)) != NULL) {
+                while ((cmd = ub_cmdq_peek(sc)) != NULL) {
                         cmd->error = -ENOTCONN;
                         cmd->state = UB_CMDST_DONE;
                         ub_cmdtr_state(sc, cmd);