5 files changed, 64 insertions, 8 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index a3c29270807e..a5726e01f839 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -572,6 +572,7 @@ void blk_cleanup_queue(struct request_queue *q)
         spin_unlock_irq(lock);
 
         bdi_unregister(q->backing_dev_info);
+        put_disk_devt(q->disk_devt);
 
         /* @q is and will stay empty, shutdown and put */
         blk_put_queue(q);
diff --git a/block/genhd.c b/block/genhd.c
index d9ccd42f3675..3631cd480295 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -572,6 +572,20 @@ exit:
         disk_part_iter_exit(&piter);
 }
 
+void put_disk_devt(struct disk_devt *disk_devt)
+{
+        if (disk_devt && atomic_dec_and_test(&disk_devt->count))
+                disk_devt->release(disk_devt);
+}
+EXPORT_SYMBOL(put_disk_devt);
+
+void get_disk_devt(struct disk_devt *disk_devt)
+{
+        if (disk_devt)
+                atomic_inc(&disk_devt->count);
+}
+EXPORT_SYMBOL(get_disk_devt);
+
 /**
  * device_add_disk - add partitioning information to kernel list
  * @parent: parent device for the disk
@@ -612,6 +626,13 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
 
         disk_alloc_events(disk);
 
+        /*
+         * Take a reference on the devt and assign it to queue since it
+         * must not be reallocated while the bdi is registered
+         */
+        disk->queue->disk_devt = disk->disk_devt;
+        get_disk_devt(disk->disk_devt);
+
         /* Register BDI before referencing it from bdev */
         bdi = disk->queue->backing_dev_info;
         bdi_register_owner(bdi, disk_to_dev(disk));
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index bd2fb4d52efa..dff709e22370 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3064,6 +3064,23 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
         put_device(&sdkp->dev);
 }
 
+struct sd_devt {
+        int idx;
+        struct disk_devt disk_devt;
+};
+
+void sd_devt_release(struct disk_devt *disk_devt)
+{
+        struct sd_devt *sd_devt = container_of(disk_devt, struct sd_devt,
+                        disk_devt);
+
+        spin_lock(&sd_index_lock);
+        ida_remove(&sd_index_ida, sd_devt->idx);
+        spin_unlock(&sd_index_lock);
+
+        kfree(sd_devt);
+}
+
 /**
  *      sd_probe - called during driver initialization and whenever a
  *      new scsi device is attached to the system. It is called once
@@ -3085,6 +3102,7 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
 static int sd_probe(struct device *dev)
 {
         struct scsi_device *sdp = to_scsi_device(dev);
+        struct sd_devt *sd_devt;
         struct scsi_disk *sdkp;
         struct gendisk *gd;
         int index;
@@ -3110,9 +3128,13 @@ static int sd_probe(struct device *dev)
         if (!sdkp)
                 goto out;
 
+        sd_devt = kzalloc(sizeof(*sd_devt), GFP_KERNEL);
+        if (!sd_devt)
+                goto out_free;
+
         gd = alloc_disk(SD_MINORS);
         if (!gd)
-                goto out_free;
+                goto out_free_devt;
 
         do {
                 if (!ida_pre_get(&sd_index_ida, GFP_KERNEL))
@@ -3128,6 +3150,11 @@ static int sd_probe(struct device *dev)
                 goto out_put;
         }
 
+        atomic_set(&sd_devt->disk_devt.count, 1);
+        sd_devt->disk_devt.release = sd_devt_release;
+        sd_devt->idx = index;
+        gd->disk_devt = &sd_devt->disk_devt;
+
         error = sd_format_disk_name("sd", index, gd->disk_name, DISK_NAME_LEN);
         if (error) {
                 sdev_printk(KERN_WARNING, sdp, "SCSI disk (sd) name length exceeded.\n");
@@ -3167,13 +3194,14 @@ static int sd_probe(struct device *dev)
         return 0;
 
  out_free_index:
-        spin_lock(&sd_index_lock);
-        ida_remove(&sd_index_ida, index);
-        spin_unlock(&sd_index_lock);
+        put_disk_devt(&sd_devt->disk_devt);
+        sd_devt = NULL;
  out_put:
         put_disk(gd);
  out_free:
         kfree(sdkp);
+ out_free_devt:
+        kfree(sd_devt);
  out:
         scsi_autopm_put_device(sdp);
         return error;
@@ -3232,10 +3260,7 @@ static void scsi_disk_release(struct device *dev)
         struct scsi_disk *sdkp = to_scsi_disk(dev);
         struct gendisk *disk = sdkp->disk;
         
-        spin_lock(&sd_index_lock);
-        ida_remove(&sd_index_ida, sdkp->index);
-        spin_unlock(&sd_index_lock);
-
+        put_disk_devt(disk->disk_devt);
         disk->private_data = NULL;
         put_disk(disk);
         put_device(&sdkp->device->sdev_gendev);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index b31137e2afd0..f84fbe55d3b3 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -433,6 +433,7 @@ struct request_queue {
         struct delayed_work     delay_work;
 
         struct backing_dev_info *backing_dev_info;
+        struct disk_devt        *disk_devt;
 
         /*
          * The queue owner gets to use this for whatever they like.
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 76f39754e7b0..a999d281a2f1 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -167,6 +167,13 @@ struct blk_integrity {
 };
 
 #endif  /* CONFIG_BLK_DEV_INTEGRITY */
+struct disk_devt {
+        atomic_t count;
+        void (*release)(struct disk_devt *disk_devt);
+};
+
+void put_disk_devt(struct disk_devt *disk_devt);
+void get_disk_devt(struct disk_devt *disk_devt);
 
 struct gendisk {
         /* major, first_minor and minors are input parameters only,
@@ -176,6 +183,7 @@ struct gendisk {
         int first_minor;
         int minors;                     /* maximum number of minors, =1 for
                                          * disks that can't be partitioned. */
+        struct disk_devt *disk_devt;
 
         char disk_name[DISK_NAME_LEN];  /* name of major driver */
         char *(*devnode)(struct gendisk *gd, umode_t *mode);