1 files changed, 478 insertions, 242 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index cb1db2979d3..b2c98c1bc03 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -41,6 +41,7 @@
 #include <linux/fs.h>
 #include <linux/blkdev.h>
 #include <linux/slab.h>
+#include <linux/idr.h>
 
 #include "rbd_types.h"
 
@@ -89,9 +90,9 @@ static int atomic_dec_return_safe(atomic_t *v)
 }
 
 #define RBD_DRV_NAME "rbd"
-#define RBD_DRV_NAME_LONG "rbd (rados block device)"
 
-#define RBD_MINORS_PER_MAJOR	256		/* max minors per blkdev */
+#define RBD_MINORS_PER_MAJOR		256
+#define RBD_SINGLE_MAJOR_PART_SHIFT	4
 
 #define RBD_SNAP_DEV_NAME_PREFIX	"snap_"
 #define RBD_MAX_SNAP_NAME_LEN	\
@@ -323,6 +324,7 @@ struct rbd_device {
 	int			dev_id;		/* blkdev unique id */
 
 	int			major;		/* blkdev assigned major */
+	int			minor;
 	struct gendisk		*disk;		/* blkdev's gendisk and rq */
 
 	u32			image_format;	/* Either 1 or 2 */
@@ -386,6 +388,17 @@ static struct kmem_cache	*rbd_img_request_cache;
 static struct kmem_cache	*rbd_obj_request_cache;
 static struct kmem_cache	*rbd_segment_name_cache;
 
+static int rbd_major;
+static DEFINE_IDA(rbd_dev_id_ida);
+
+/*
+ * Default to false for now, as single-major requires >= 0.75 version of
+ * userspace rbd utility.
+ */
+static bool single_major = false;
+module_param(single_major, bool, S_IRUGO);
+MODULE_PARM_DESC(single_major, "Use a single major number for all rbd devices (default: false)");
+
 static int rbd_img_request_submit(struct rbd_img_request *img_request);
 
 static void rbd_dev_device_release(struct device *dev);
@@ -394,18 +407,52 @@ static ssize_t rbd_add(struct bus_type *bus, const char *buf,
 		       size_t count);
 static ssize_t rbd_remove(struct bus_type *bus, const char *buf,
 			  size_t count);
+static ssize_t rbd_add_single_major(struct bus_type *bus, const char *buf,
+				    size_t count);
+static ssize_t rbd_remove_single_major(struct bus_type *bus, const char *buf,
+				       size_t count);
 static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping);
 static void rbd_spec_put(struct rbd_spec *spec);
 
+static int rbd_dev_id_to_minor(int dev_id)
+{
+	return dev_id << RBD_SINGLE_MAJOR_PART_SHIFT;
+}
+
+static int minor_to_rbd_dev_id(int minor)
+{
+	return minor >> RBD_SINGLE_MAJOR_PART_SHIFT;
+}
+
 static BUS_ATTR(add, S_IWUSR, NULL, rbd_add);
 static BUS_ATTR(remove, S_IWUSR, NULL, rbd_remove);
+static BUS_ATTR(add_single_major, S_IWUSR, NULL, rbd_add_single_major);
+static BUS_ATTR(remove_single_major, S_IWUSR, NULL, rbd_remove_single_major);
 
 static struct attribute *rbd_bus_attrs[] = {
 	&bus_attr_add.attr,
 	&bus_attr_remove.attr,
+	&bus_attr_add_single_major.attr,
+	&bus_attr_remove_single_major.attr,
 	NULL,
 };
-ATTRIBUTE_GROUPS(rbd_bus);
+
+static umode_t rbd_bus_is_visible(struct kobject *kobj,
+				  struct attribute *attr, int index)
+{
+	if (!single_major &&
+	    (attr == &bus_attr_add_single_major.attr ||
+	     attr == &bus_attr_remove_single_major.attr))
+		return 0;
+
+	return attr->mode;
+}
+
+static const struct attribute_group rbd_bus_group = {
+	.attrs = rbd_bus_attrs,
+	.is_visible = rbd_bus_is_visible,
+};
+__ATTRIBUTE_GROUPS(rbd_bus);
 
 static struct bus_type rbd_bus_type = {
 	.name		= "rbd",
@@ -494,7 +541,6 @@ static int rbd_open(struct block_device *bdev, fmode_t mode)
 		return -ENOENT;
 
 	(void) get_device(&rbd_dev->dev);
-	set_device_ro(bdev, rbd_dev->mapping.read_only);
 
 	return 0;
 }
@@ -512,10 +558,76 @@ static void rbd_release(struct gendisk *disk, fmode_t mode)
 	put_device(&rbd_dev->dev);
 }
 
+static int rbd_ioctl_set_ro(struct rbd_device *rbd_dev, unsigned long arg)
+{
+	int ret = 0;
+	int val;
+	bool ro;
+	bool ro_changed = false;
+
+	/* get_user() may sleep, so call it before taking rbd_dev->lock */
+	if (get_user(val, (int __user *)(arg)))
+		return -EFAULT;
+
+	ro = val ? true : false;
+	/* Snapshot doesn't allow to write*/
+	if (rbd_dev->spec->snap_id != CEPH_NOSNAP && !ro)
+		return -EROFS;
+
+	spin_lock_irq(&rbd_dev->lock);
+	/* prevent others open this device */
+	if (rbd_dev->open_count > 1) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	if (rbd_dev->mapping.read_only != ro) {
+		rbd_dev->mapping.read_only = ro;
+		ro_changed = true;
+	}
+
+out:
+	spin_unlock_irq(&rbd_dev->lock);
+	/* set_disk_ro() may sleep, so call it after releasing rbd_dev->lock */
+	if (ret == 0 && ro_changed)
+		set_disk_ro(rbd_dev->disk, ro ? 1 : 0);
+
+	return ret;
+}
+
+static int rbd_ioctl(struct block_device *bdev, fmode_t mode,
+			unsigned int cmd, unsigned long arg)
+{
+	struct rbd_device *rbd_dev = bdev->bd_disk->private_data;
+	int ret = 0;
+
+	switch (cmd) {
+	case BLKROSET:
+		ret = rbd_ioctl_set_ro(rbd_dev, arg);
+		break;
+	default:
+		ret = -ENOTTY;
+	}
+
+	return ret;
+}
+
+#ifdef CONFIG_COMPAT
+static int rbd_compat_ioctl(struct block_device *bdev, fmode_t mode,
+				unsigned int cmd, unsigned long arg)
+{
+	return rbd_ioctl(bdev, mode, cmd, arg);
+}
+#endif /* CONFIG_COMPAT */
+
 static const struct block_device_operations rbd_bd_ops = {
 	.owner			= THIS_MODULE,
 	.open			= rbd_open,
 	.release		= rbd_release,
+	.ioctl			= rbd_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl		= rbd_compat_ioctl,
+#endif
 };
 
 /*
@@ -1041,9 +1153,9 @@ static const char *rbd_segment_name(struct rbd_device *rbd_dev, u64 offset)
 	name_format = "%s.%012llx";
 	if (rbd_dev->image_format == 2)
 		name_format = "%s.%016llx";
-	ret = snprintf(name, MAX_OBJ_NAME_SIZE + 1, name_format,
+	ret = snprintf(name, CEPH_MAX_OID_NAME_LEN + 1, name_format,
 			rbd_dev->header.object_prefix, segment);
-	if (ret < 0 || ret > MAX_OBJ_NAME_SIZE) {
+	if (ret < 0 || ret > CEPH_MAX_OID_NAME_LEN) {
 		pr_err("error formatting segment name for #%llu (%d)\n",
 			segment, ret);
 		kfree(name);
@@ -1109,23 +1221,23 @@ static void bio_chain_put(struct bio *chain)
  */
 static void zero_bio_chain(struct bio *chain, int start_ofs)
 {
-	struct bio_vec *bv;
+	struct bio_vec bv;
+	struct bvec_iter iter;
 	unsigned long flags;
 	void *buf;
-	int i;
 	int pos = 0;
 
 	while (chain) {
-		bio_for_each_segment(bv, chain, i) {
-			if (pos + bv->bv_len > start_ofs) {
+		bio_for_each_segment(bv, chain, iter) {
+			if (pos + bv.bv_len > start_ofs) {
 				int remainder = max(start_ofs - pos, 0);
-				buf = bvec_kmap_irq(bv, &flags);
+				buf = bvec_kmap_irq(&bv, &flags);
 				memset(buf + remainder, 0,
-				       bv->bv_len - remainder);
-				flush_dcache_page(bv->bv_page);
+				       bv.bv_len - remainder);
+				flush_dcache_page(bv.bv_page);
 				bvec_kunmap_irq(buf, &flags);
 			}
-			pos += bv->bv_len;
+			pos += bv.bv_len;
 		}
 
 		chain = chain->bi_next;
@@ -1173,74 +1285,14 @@ static struct bio *bio_clone_range(struct bio *bio_src,
 					unsigned int len,
 					gfp_t gfpmask)
 {
-	struct bio_vec *bv;
-	unsigned int resid;
-	unsigned short idx;
-	unsigned int voff;
-	unsigned short end_idx;
-	unsigned short vcnt;
 	struct bio *bio;
 
-	/* Handle the easy case for the caller */
-
-	if (!offset && len == bio_src->bi_size)
-		return bio_clone(bio_src, gfpmask);
-
-	if (WARN_ON_ONCE(!len))
-		return NULL;
-	if (WARN_ON_ONCE(len > bio_src->bi_size))
-		return NULL;
-	if (WARN_ON_ONCE(offset > bio_src->bi_size - len))
-		return NULL;
-
-	/* Find first affected segment... */
-
-	resid = offset;
-	bio_for_each_segment(bv, bio_src, idx) {
-		if (resid < bv->bv_len)
-			break;
-		resid -= bv->bv_len;
-	}
-	voff = resid;
-
-	/* ...and the last affected segment */
-
-	resid += len;
-	__bio_for_each_segment(bv, bio_src, end_idx, idx) {
-		if (resid <= bv->bv_len)
-			break;
-		resid -= bv->bv_len;
-	}
-	vcnt = end_idx - idx + 1;
-
-	/* Build the clone */
-
-	bio = bio_alloc(gfpmask, (unsigned int) vcnt);
+	bio = bio_clone(bio_src, gfpmask);
 	if (!bio)
 		return NULL;	/* ENOMEM */
 
-	bio->bi_bdev = bio_src->bi_bdev;
-	bio->bi_sector = bio_src->bi_sector + (offset >> SECTOR_SHIFT);
-	bio->bi_rw = bio_src->bi_rw;
-	bio->bi_flags |= 1 << BIO_CLONED;
-
-	/*
-	 * Copy over our part of the bio_vec, then update the first
-	 * and last (or only) entries.
-	 */
-	memcpy(&bio->bi_io_vec[0], &bio_src->bi_io_vec[idx],
-			vcnt * sizeof (struct bio_vec));
-	bio->bi_io_vec[0].bv_offset += voff;
-	if (vcnt > 1) {
-		bio->bi_io_vec[0].bv_len -= voff;
-		bio->bi_io_vec[vcnt - 1].bv_len = resid;
-	} else {
-		bio->bi_io_vec[0].bv_len = len;
-	}
-
-	bio->bi_vcnt = vcnt;
-	bio->bi_size = len;
-	bio->bi_idx = 0;
+	bio_advance(bio, offset);
+	bio->bi_iter.bi_size = len;
 
 	return bio;
 }
@@ -1271,7 +1323,7 @@ static struct bio *bio_chain_clone_range(struct bio **bio_src,
 
 	/* Build up a chain of clone bios up to the limit */
 
-	if (!bi || off >= bi->bi_size || !len)
+	if (!bi || off >= bi->bi_iter.bi_size || !len)
 		return NULL;		/* Nothing to clone */
 
 	end = &chain;
@@ -1283,7 +1335,7 @@ static struct bio *bio_chain_clone_range(struct bio **bio_src,
 			rbd_warn(NULL, "bio_chain exhausted with %u left", len);
 			goto out_err;	/* EINVAL; ran out of bio's */
 		}
-		bi_size = min_t(unsigned int, bi->bi_size - off, len);
+		bi_size = min_t(unsigned int, bi->bi_iter.bi_size - off, len);
 		bio = bio_clone_range(bi, off, bi_size, gfpmask);
 		if (!bio)
 			goto out_err;	/* ENOMEM */
@@ -1292,7 +1344,7 @@ static struct bio *bio_chain_clone_range(struct bio **bio_src,
 		end = &bio->bi_next;
 
 		off += bi_size;
-		if (off == bi->bi_size) {
+		if (off == bi->bi_iter.bi_size) {
 			bi = bi->bi_next;
 			off = 0;
 		}
@@ -1379,6 +1431,14 @@ static bool obj_request_exists_test(struct rbd_obj_request *obj_request)
 	return test_bit(OBJ_REQ_EXISTS, &obj_request->flags) != 0;
 }
 
+static bool obj_request_overlaps_parent(struct rbd_obj_request *obj_request)
+{
+	struct rbd_device *rbd_dev = obj_request->img_request->rbd_dev;
+
+	return obj_request->img_offset <
+	    round_up(rbd_dev->parent_overlap, rbd_obj_bytes(&rbd_dev->header));
+}
+
 static void rbd_obj_request_get(struct rbd_obj_request *obj_request)
 {
 	dout("%s: obj %p (was %d)\n", __func__, obj_request,
@@ -1395,6 +1455,13 @@ static void rbd_obj_request_put(struct rbd_obj_request *obj_request)
 	kref_put(&obj_request->kref, rbd_obj_request_destroy);
 }
 
+static void rbd_img_request_get(struct rbd_img_request *img_request)
+{
+	dout("%s: img %p (was %d)\n", __func__, img_request,
+	     atomic_read(&img_request->kref.refcount));
+	kref_get(&img_request->kref);
+}
+
 static bool img_request_child_test(struct rbd_img_request *img_request);
 static void rbd_parent_request_destroy(struct kref *kref);
 static void rbd_img_request_destroy(struct kref *kref);
@@ -1667,7 +1734,7 @@ static void rbd_osd_req_callback(struct ceph_osd_request *osd_req,
 	if (osd_req->r_result < 0)
 		obj_request->result = osd_req->r_result;
 
-	BUG_ON(osd_req->r_num_ops > 2);
+	rbd_assert(osd_req->r_num_ops <= CEPH_OSD_MAX_OP);
 
 	/*
 	 * We support a 64-bit length, but ultimately it has to be
@@ -1675,11 +1742,15 @@ static void rbd_osd_req_callback(struct ceph_osd_request *osd_req,
 	 */
 	obj_request->xferred = osd_req->r_reply_op_len[0];
 	rbd_assert(obj_request->xferred < (u64)UINT_MAX);
+
 	opcode = osd_req->r_ops[0].op;
 	switch (opcode) {
 	case CEPH_OSD_OP_READ:
 		rbd_osd_read_callback(obj_request);
 		break;
+	case CEPH_OSD_OP_SETALLOCHINT:
+		rbd_assert(osd_req->r_ops[1].op == CEPH_OSD_OP_WRITE);
+		/* fall through */
 	case CEPH_OSD_OP_WRITE:
 		rbd_osd_write_callback(obj_request);
 		break;
@@ -1728,9 +1799,16 @@ static void rbd_osd_req_format_write(struct rbd_obj_request *obj_request)
 			snapc, CEPH_NOSNAP, &mtime);
 }
 
+/*
+ * Create an osd request.  A read request has one osd op (read).
+ * A write request has either one (watch) or two (hint+write) osd ops.
+ * (All rbd data writes are prefixed with an allocation hint op, but
+ * technically osd watch is a write request, hence this distinction.)
+ */
 static struct ceph_osd_request *rbd_osd_req_create(
 					struct rbd_device *rbd_dev,
 					bool write_request,
+					unsigned int num_ops,
 					struct rbd_obj_request *obj_request)
 {
 	struct ceph_snap_context *snapc = NULL;
@@ -1746,10 +1824,13 @@ static struct ceph_osd_request *rbd_osd_req_create(
 			snapc = img_request->snapc;
 	}
 
-	/* Allocate and initialize the request, for the single op */
+	rbd_assert(num_ops == 1 || (write_request && num_ops == 2));
+
+	/* Allocate and initialize the request, for the num_ops ops */
 
 	osdc = &rbd_dev->rbd_client->client->osdc;
-	osd_req = ceph_osdc_alloc_request(osdc, snapc, 1, false, GFP_ATOMIC);
+	osd_req = ceph_osdc_alloc_request(osdc, snapc, num_ops, false,
+					  GFP_ATOMIC);
 	if (!osd_req)
 		return NULL;	/* ENOMEM */
 
@@ -1761,19 +1842,16 @@ static struct ceph_osd_request *rbd_osd_req_create(
 	osd_req->r_callback = rbd_osd_req_callback;
 	osd_req->r_priv = obj_request;
 
-	osd_req->r_oid_len = strlen(obj_request->object_name);
-	rbd_assert(osd_req->r_oid_len < sizeof (osd_req->r_oid));
-	memcpy(osd_req->r_oid, obj_request->object_name, osd_req->r_oid_len);
-
-	osd_req->r_file_layout = rbd_dev->layout;	/* struct */
+	osd_req->r_base_oloc.pool = ceph_file_layout_pg_pool(rbd_dev->layout);
+	ceph_oid_set_name(&osd_req->r_base_oid, obj_request->object_name);
 
 	return osd_req;
 }
 
 /*
  * Create a copyup osd request based on the information in the
- * object request supplied.  A copyup request has two osd ops,
- * a copyup method call, and a "normal" write request.
+ * object request supplied.  A copyup request has three osd ops,
+ * a copyup method call, a hint op, and a write op.
  */
 static struct ceph_osd_request *
 rbd_osd_req_create_copyup(struct rbd_obj_request *obj_request)
@@ -1789,12 +1867,12 @@ rbd_osd_req_create_copyup(struct rbd_obj_request *obj_request)
 	rbd_assert(img_request);
 	rbd_assert(img_request_write_test(img_request));
 
-	/* Allocate and initialize the request, for the two ops */
+	/* Allocate and initialize the request, for the three ops */
 
 	snapc = img_request->snapc;
 	rbd_dev = img_request->rbd_dev;
 	osdc = &rbd_dev->rbd_client->client->osdc;
-	osd_req = ceph_osdc_alloc_request(osdc, snapc, 2, false, GFP_ATOMIC);
+	osd_req = ceph_osdc_alloc_request(osdc, snapc, 3, false, GFP_ATOMIC);
 	if (!osd_req)
 		return NULL;	/* ENOMEM */
 
@@ -1802,11 +1880,8 @@ rbd_osd_req_create_copyup(struct rbd_obj_request *obj_request)
 	osd_req->r_callback = rbd_osd_req_callback;
 	osd_req->r_priv = obj_request;
 
-	osd_req->r_oid_len = strlen(obj_request->object_name);
-	rbd_assert(osd_req->r_oid_len < sizeof (osd_req->r_oid));
-	memcpy(osd_req->r_oid, obj_request->object_name, osd_req->r_oid_len);
-
-	osd_req->r_file_layout = rbd_dev->layout;	/* struct */
+	osd_req->r_base_oloc.pool = ceph_file_layout_pg_pool(rbd_dev->layout);
+	ceph_oid_set_name(&osd_req->r_base_oid, obj_request->object_name);
 
 	return osd_req;
 }
@@ -2128,7 +2203,6 @@ static void rbd_img_obj_callback(struct rbd_obj_request *obj_request)
 	rbd_assert(img_request->obj_request_count > 0);
 	rbd_assert(which != BAD_WHICH);
 	rbd_assert(which < img_request->obj_request_count);
-	rbd_assert(which >= img_request->next_completion);
 
 	spin_lock_irq(&img_request->completion_lock);
 	if (which != img_request->next_completion)
@@ -2148,6 +2222,7 @@ static void rbd_img_obj_callback(struct rbd_obj_request *obj_request)
 	img_request->next_completion = which;
 out:
 	spin_unlock_irq(&img_request->completion_lock);
+	rbd_img_request_put(img_request);
 
 	if (!more)
 		rbd_img_request_complete(img_request);
@@ -2186,7 +2261,8 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 
 	if (type == OBJ_REQUEST_BIO) {
 		bio_list = data_desc;
-		rbd_assert(img_offset == bio_list->bi_sector << SECTOR_SHIFT);
+		rbd_assert(img_offset ==
+			   bio_list->bi_iter.bi_sector << SECTOR_SHIFT);
 	} else {
 		rbd_assert(type == OBJ_REQUEST_PAGES);
 		pages = data_desc;
@@ -2197,6 +2273,7 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 		const char *object_name;
 		u64 offset;
 		u64 length;
+		unsigned int which = 0;
 
 		object_name = rbd_segment_name(rbd_dev, img_offset);
 		if (!object_name)
@@ -2209,6 +2286,7 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 		rbd_segment_name_free(object_name);
 		if (!obj_request)
 			goto out_unwind;
+
 		/*
 		 * set obj_request->img_request before creating the
 		 * osd_request so that it gets the right snapc
@@ -2226,7 +2304,7 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 								clone_size,
 								GFP_ATOMIC);
 			if (!obj_request->bio_list)
-				goto out_partial;
+				goto out_unwind;
 		} else {
 			unsigned int page_count;
 
@@ -2239,19 +2317,28 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 		}
 
 		osd_req = rbd_osd_req_create(rbd_dev, write_request,
-						obj_request);
+					     (write_request ? 2 : 1),
+					     obj_request);
 		if (!osd_req)
-			goto out_partial;
+			goto out_unwind;
 		obj_request->osd_req = osd_req;
 		obj_request->callback = rbd_img_obj_callback;
+		rbd_img_request_get(img_request);
 
-		osd_req_op_extent_init(osd_req, 0, opcode, offset, length,
-						0, 0);
+		if (write_request) {
+			osd_req_op_alloc_hint_init(osd_req, which,
+					     rbd_obj_bytes(&rbd_dev->header),
+					     rbd_obj_bytes(&rbd_dev->header));
+			which++;
+		}
+
+		osd_req_op_extent_init(osd_req, which, opcode, offset, length,
+				       0, 0);
 		if (type == OBJ_REQUEST_BIO)
-			osd_req_op_extent_osd_data_bio(osd_req, 0,
+			osd_req_op_extent_osd_data_bio(osd_req, which,
 					obj_request->bio_list, length);
 		else
-			osd_req_op_extent_osd_data_pages(osd_req, 0,
+			osd_req_op_extent_osd_data_pages(osd_req, which,
 					obj_request->pages, length,
 					offset & ~PAGE_MASK, false, false);
 
@@ -2268,11 +2355,9 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 
 	return 0;
 
-out_partial:
-	rbd_obj_request_put(obj_request);
 out_unwind:
 	for_each_obj_request_safe(img_request, obj_request, next_obj_request)
-		rbd_obj_request_put(obj_request);
+		rbd_img_obj_request_del(img_request, obj_request);
 
 	return -ENOMEM;
 }
@@ -2372,7 +2457,7 @@ rbd_img_obj_parent_read_full_callback(struct rbd_img_request *img_request)
 
 	/*
 	 * The original osd request is of no use to use any more.
-	 * We need a new one that can hold the two ops in a copyup
+	 * We need a new one that can hold the three ops in a copyup
 	 * request.  Allocate the new copyup osd request for the
 	 * original request, and release the old one.
 	 */
@@ -2391,17 +2476,22 @@ rbd_img_obj_parent_read_full_callback(struct rbd_img_request *img_request)
 	osd_req_op_cls_request_data_pages(osd_req, 0, pages, parent_length, 0,
 						false, false);
 
-	/* Then the original write request op */
+	/* Then the hint op */
+
+	osd_req_op_alloc_hint_init(osd_req, 1, rbd_obj_bytes(&rbd_dev->header),
+				   rbd_obj_bytes(&rbd_dev->header));
+
+	/* And the original write request op */
 
 	offset = orig_request->offset;
 	length = orig_request->length;
-	osd_req_op_extent_init(osd_req, 1, CEPH_OSD_OP_WRITE,
+	osd_req_op_extent_init(osd_req, 2, CEPH_OSD_OP_WRITE,
 					offset, length, 0, 0);
 	if (orig_request->type == OBJ_REQUEST_BIO)
-		osd_req_op_extent_osd_data_bio(osd_req, 1,
+		osd_req_op_extent_osd_data_bio(osd_req, 2,
 					orig_request->bio_list, length);
 	else
-		osd_req_op_extent_osd_data_pages(osd_req, 1,
+		osd_req_op_extent_osd_data_pages(osd_req, 2,
 					orig_request->pages, length,
 					offset & ~PAGE_MASK, false, false);
 
@@ -2622,8 +2712,8 @@ static int rbd_img_obj_exists_submit(struct rbd_obj_request *obj_request)
 
 	rbd_assert(obj_request->img_request);
 	rbd_dev = obj_request->img_request->rbd_dev;
-	stat_request->osd_req = rbd_osd_req_create(rbd_dev, false,
-						stat_request);
+	stat_request->osd_req = rbd_osd_req_create(rbd_dev, false, 1,
+						   stat_request);
 	if (!stat_request->osd_req)
 		goto out;
 	stat_request->callback = rbd_img_obj_exists_callback;
@@ -2666,7 +2756,7 @@ static int rbd_img_obj_request_submit(struct rbd_obj_request *obj_request)
 	 */
 	if (!img_request_write_test(img_request) ||
 		!img_request_layered_test(img_request) ||
-		rbd_dev->parent_overlap <= obj_request->img_offset ||
+		!obj_request_overlaps_parent(obj_request) ||
 		((known = obj_request_known_test(obj_request)) &&
 			obj_request_exists_test(obj_request))) {
 
@@ -2826,7 +2916,8 @@ static int rbd_obj_notify_ack_sync(struct rbd_device *rbd_dev, u64 notify_id)
 		return -ENOMEM;
 
 	ret = -ENOMEM;
-	obj_request->osd_req = rbd_osd_req_create(rbd_dev, false, obj_request);
+	obj_request->osd_req = rbd_osd_req_create(rbd_dev, false, 1,
+						  obj_request);
 	if (!obj_request->osd_req)
 		goto out;
 
@@ -2863,55 +2954,55 @@ static void rbd_watch_cb(u64 ver, u64 notify_id, u8 opcode, void *data)
 }
 
 /*
- * Request sync osd watch/unwatch.  The value of "start" determines
- * whether a watch request is being initiated or torn down.
+ * Initiate a watch request, synchronously.
  */
-static int rbd_dev_header_watch_sync(struct rbd_device *rbd_dev, bool start)
+static int rbd_dev_header_watch_sync(struct rbd_device *rbd_dev)
 {
 	struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc;
 	struct rbd_obj_request *obj_request;
 	int ret;
 
-	rbd_assert(start ^ !!rbd_dev->watch_event);
-	rbd_assert(start ^ !!rbd_dev->watch_request);
+	rbd_assert(!rbd_dev->watch_event);
+	rbd_assert(!rbd_dev->watch_request);
 
-	if (start) {
-		ret = ceph_osdc_create_event(osdc, rbd_watch_cb, rbd_dev,
-						&rbd_dev->watch_event);
-		if (ret < 0)
-			return ret;
-		rbd_assert(rbd_dev->watch_event != NULL);
-	}
+	ret = ceph_osdc_create_event(osdc, rbd_watch_cb, rbd_dev,
+				     &rbd_dev->watch_event);
+	if (ret < 0)
+		return ret;
+
+	rbd_assert(rbd_dev->watch_event);
 
-	ret = -ENOMEM;
 	obj_request = rbd_obj_request_create(rbd_dev->header_name, 0, 0,
-							OBJ_REQUEST_NODATA);
-	if (!obj_request)
+					     OBJ_REQUEST_NODATA);
+	if (!obj_request) {
+		ret = -ENOMEM;
 		goto out_cancel;
+	}
 
-	obj_request->osd_req = rbd_osd_req_create(rbd_dev, true, obj_request);
-	if (!obj_request->osd_req)
-		goto out_cancel;
+	obj_request->osd_req = rbd_osd_req_create(rbd_dev, true, 1,
+						  obj_request);
+	if (!obj_request->osd_req) {
+		ret = -ENOMEM;
+		goto out_put;
+	}
 
-	if (start)
-		ceph_osdc_set_request_linger(osdc, obj_request->osd_req);
-	else
-		ceph_osdc_unregister_linger_request(osdc,
-					rbd_dev->watch_request->osd_req);
+	ceph_osdc_set_request_linger(osdc, obj_request->osd_req);
 
 	osd_req_op_watch_init(obj_request->osd_req, 0, CEPH_OSD_OP_WATCH,
-				rbd_dev->watch_event->cookie, 0, start ? 1 : 0);
+			      rbd_dev->watch_event->cookie, 0, 1);
 	rbd_osd_req_format_write(obj_request);
 
 	ret = rbd_obj_request_submit(osdc, obj_request);
 	if (ret)
-		goto out_cancel;
+		goto out_linger;
+
 	ret = rbd_obj_request_wait(obj_request);
 	if (ret)
-		goto out_cancel;
+		goto out_linger;
+
 	ret = obj_request->result;
 	if (ret)
-		goto out_cancel;
+		goto out_linger;
 
 	/*
 	 * A watch request is set to linger, so the underlying osd
@@ -2921,26 +3012,90 @@ static int rbd_dev_header_watch_sync(struct rbd_device *rbd_dev, bool start)
 	 * it.  We'll drop that reference (below) after we've
 	 * unregistered it.
 	 */
-	if (start) {
-		rbd_dev->watch_request = obj_request;
+	rbd_dev->watch_request = obj_request;
 
-		return 0;
+	return 0;
+
+out_linger:
+	ceph_osdc_unregister_linger_request(osdc, obj_request->osd_req);
+out_put:
+	rbd_obj_request_put(obj_request);
+out_cancel:
+	ceph_osdc_cancel_event(rbd_dev->watch_event);
+	rbd_dev->watch_event = NULL;
+
+	return ret;
+}
+
+/*
+ * Tear down a watch request, synchronously.
+ */
+static int __rbd_dev_header_unwatch_sync(struct rbd_device *rbd_dev)
+{
+	struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc;
+	struct rbd_obj_request *obj_request;
+	int ret;
+
+	rbd_assert(rbd_dev->watch_event);
+	rbd_assert(rbd_dev->watch_request);
+
+	obj_request = rbd_obj_request_create(rbd_dev->header_name, 0, 0,
+					     OBJ_REQUEST_NODATA);
+	if (!obj_request) {
+		ret = -ENOMEM;
+		goto out_cancel;
 	}
 
+	obj_request->osd_req = rbd_osd_req_create(rbd_dev, true, 1,
+						  obj_request);
+	if (!obj_request->osd_req) {
+		ret = -ENOMEM;
+		goto out_put;
+	}
+
+	osd_req_op_watch_init(obj_request->osd_req, 0, CEPH_OSD_OP_WATCH,
+			      rbd_dev->watch_event->cookie, 0, 0);
+	rbd_osd_req_format_write(obj_request);
+
+	ret = rbd_obj_request_submit(osdc, obj_request);
+	if (ret)
+		goto out_put;
+
+	ret = rbd_obj_request_wait(obj_request);
+	if (ret)
+		goto out_put;
+
+	ret = obj_request->result;
+	if (ret)
+		goto out_put;
+
 	/* We have successfully torn down the watch request */
 
+	ceph_osdc_unregister_linger_request(osdc,
+					    rbd_dev->watch_request->osd_req);
 	rbd_obj_request_put(rbd_dev->watch_request);
 	rbd_dev->watch_request = NULL;
+
+out_put:
+	rbd_obj_request_put(obj_request);
 out_cancel:
-	/* Cancel the event if we're tearing down, or on error */
 	ceph_osdc_cancel_event(rbd_dev->watch_event);
 	rbd_dev->watch_event = NULL;
-	if (obj_request)
-		rbd_obj_request_put(obj_request);
 
 	return ret;
 }
 
+static void rbd_dev_header_unwatch_sync(struct rbd_device *rbd_dev)
+{
+	int ret;
+
+	ret = __rbd_dev_header_unwatch_sync(rbd_dev);
+	if (ret) {
+		rbd_warn(rbd_dev, "unable to tear down watch request: %d\n",
+			 ret);
+	}
+}
+
 /*
  * Synchronous osd object method call.  Returns the number of bytes
  * returned in the outbound buffer, or a negative error code.
@@ -2981,7 +3136,8 @@ static int rbd_obj_method_sync(struct rbd_device *rbd_dev,
 	obj_request->pages = pages;
 	obj_request->page_count = page_count;
 
-	obj_request->osd_req = rbd_osd_req_create(rbd_dev, false, obj_request);
+	obj_request->osd_req = rbd_osd_req_create(rbd_dev, false, 1,
+						  obj_request);
 	if (!obj_request->osd_req)
 		goto out;
 
@@ -3031,7 +3187,6 @@ static void rbd_request_fn(struct request_queue *q)
 		__releases(q->queue_lock) __acquires(q->queue_lock)
 {
 	struct rbd_device *rbd_dev = q->queuedata;
-	bool read_only = rbd_dev->mapping.read_only;
 	struct request *rq;
 	int result;
 
@@ -3067,7 +3222,7 @@ static void rbd_request_fn(struct request_queue *q)
 
 		if (write_request) {
 			result = -EROFS;
-			if (read_only)
+			if (rbd_dev->mapping.read_only)
 				goto end_request;
 			rbd_assert(rbd_dev->spec->snap_id == CEPH_NOSNAP);
 		}
@@ -3214,7 +3369,8 @@ static int rbd_obj_read_sync(struct rbd_device *rbd_dev,
 	obj_request->pages = pages;
 	obj_request->page_count = page_count;
 
-	obj_request->osd_req = rbd_osd_req_create(rbd_dev, false, obj_request);
+	obj_request->osd_req = rbd_osd_req_create(rbd_dev, false, 1,
+						  obj_request);
 	if (!obj_request->osd_req)
 		goto out;
 
@@ -3388,14 +3544,18 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
 	u64 segment_size;
 
 	/* create gendisk info */
-	disk = alloc_disk(RBD_MINORS_PER_MAJOR);
+	disk = alloc_disk(single_major ?
+			  (1 << RBD_SINGLE_MAJOR_PART_SHIFT) :
+			  RBD_MINORS_PER_MAJOR);
 	if (!disk)
 		return -ENOMEM;
 
 	snprintf(disk->disk_name, sizeof(disk->disk_name), RBD_DRV_NAME "%d",
 		 rbd_dev->dev_id);
 	disk->major = rbd_dev->major;
-	disk->first_minor = 0;
+	disk->first_minor = rbd_dev->minor;
+	if (single_major)
+		disk->flags |= GENHD_FL_EXT_DEVT;
 	disk->fops = &rbd_bd_ops;
 	disk->private_data = rbd_dev;
 
@@ -3467,7 +3627,14 @@ static ssize_t rbd_major_show(struct device *dev,
 		return sprintf(buf, "%d\n", rbd_dev->major);
 
 	return sprintf(buf, "(none)\n");
+}
+
+static ssize_t rbd_minor_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
 
+	return sprintf(buf, "%d\n", rbd_dev->minor);
 }
 
 static ssize_t rbd_client_id_show(struct device *dev,
@@ -3589,6 +3756,7 @@ static ssize_t rbd_image_refresh(struct device *dev,
 static DEVICE_ATTR(size, S_IRUGO, rbd_size_show, NULL);
 static DEVICE_ATTR(features, S_IRUGO, rbd_features_show, NULL);
 static DEVICE_ATTR(major, S_IRUGO, rbd_major_show, NULL);
+static DEVICE_ATTR(minor, S_IRUGO, rbd_minor_show, NULL);
 static DEVICE_ATTR(client_id, S_IRUGO, rbd_client_id_show, NULL);
 static DEVICE_ATTR(pool, S_IRUGO, rbd_pool_show, NULL);
 static DEVICE_ATTR(pool_id, S_IRUGO, rbd_pool_id_show, NULL);
@@ -3602,6 +3770,7 @@ static struct attribute *rbd_attrs[] = {
 	&dev_attr_size.attr,
 	&dev_attr_features.attr,
 	&dev_attr_major.attr,
+	&dev_attr_minor.attr,
 	&dev_attr_client_id.attr,
 	&dev_attr_pool.attr,
 	&dev_attr_pool_id.attr,
@@ -4372,21 +4541,29 @@ static void rbd_bus_del_dev(struct rbd_device *rbd_dev)
 	device_unregister(&rbd_dev->dev);
 }
 
-static atomic64_t rbd_dev_id_max = ATOMIC64_INIT(0);
-
 /*
  * Get a unique rbd identifier for the given new rbd_dev, and add
- * the rbd_dev to the global list.  The minimum rbd id is 1.
+ * the rbd_dev to the global list.
  */
-static void rbd_dev_id_get(struct rbd_device *rbd_dev)
+static int rbd_dev_id_get(struct rbd_device *rbd_dev)
 {
-	rbd_dev->dev_id = atomic64_inc_return(&rbd_dev_id_max);
+	int new_dev_id;
+
+	new_dev_id = ida_simple_get(&rbd_dev_id_ida,
+				    0, minor_to_rbd_dev_id(1 << MINORBITS),
+				    GFP_KERNEL);
+	if (new_dev_id < 0)
+		return new_dev_id;
+
+	rbd_dev->dev_id = new_dev_id;
 
 	spin_lock(&rbd_dev_list_lock);
 	list_add_tail(&rbd_dev->node, &rbd_dev_list);
 	spin_unlock(&rbd_dev_list_lock);
-	dout("rbd_dev %p given dev id %llu\n", rbd_dev,
-		(unsigned long long) rbd_dev->dev_id);
+
+	dout("rbd_dev %p given dev id %d\n", rbd_dev, rbd_dev->dev_id);
+
+	return 0;
 }
 
 /*
@@ -4395,49 +4572,13 @@ static void rbd_dev_id_get(struct rbd_device *rbd_dev)
  */
 static void rbd_dev_id_put(struct rbd_device *rbd_dev)
 {
-	struct list_head *tmp;
-	int rbd_id = rbd_dev->dev_id;
-	int max_id;
-
-	rbd_assert(rbd_id > 0);
-
-	dout("rbd_dev %p released dev id %llu\n", rbd_dev,
-		(unsigned long long) rbd_dev->dev_id);
 	spin_lock(&rbd_dev_list_lock);
 	list_del_init(&rbd_dev->node);
-
-	/*
-	 * If the id being "put" is not the current maximum, there
-	 * is nothing special we need to do.
-	 */
-	if (rbd_id != atomic64_read(&rbd_dev_id_max)) {
-		spin_unlock(&rbd_dev_list_lock);
-		return;
-	}
-
-	/*
-	 * We need to update the current maximum id.  Search the
-	 * list to find out what it is.  We're more likely to find
-	 * the maximum at the end, so search the list backward.
-	 */
-	max_id = 0;
-	list_for_each_prev(tmp, &rbd_dev_list) {
-		struct rbd_device *rbd_dev;
-
-		rbd_dev = list_entry(tmp, struct rbd_device, node);
-		if (rbd_dev->dev_id > max_id)
-			max_id = rbd_dev->dev_id;
-	}
 	spin_unlock(&rbd_dev_list_lock);
 
-	/*
-	 * The max id could have been updated by rbd_dev_id_get(), in
-	 * which case it now accurately reflects the new maximum.
-	 * Be careful not to overwrite the maximum value in that
-	 * case.
-	 */
-	atomic64_cmpxchg(&rbd_dev_id_max, rbd_id, max_id);
-	dout("  max dev id has been reset\n");
+	ida_simple_remove(&rbd_dev_id_ida, rbd_dev->dev_id);
+
+	dout("rbd_dev %p released dev id %d\n", rbd_dev, rbd_dev->dev_id);
 }
 
 /*
@@ -4670,6 +4811,38 @@ out_err:
 }
 
 /*
+ * Return pool id (>= 0) or a negative error code.
+ */
+static int rbd_add_get_pool_id(struct rbd_client *rbdc, const char *pool_name)
+{
+	u64 newest_epoch;
+	unsigned long timeout = rbdc->client->options->mount_timeout * HZ;
+	int tries = 0;
+	int ret;
+
+again:
+	ret = ceph_pg_poolid_by_name(rbdc->client->osdc.osdmap, pool_name);
+	if (ret == -ENOENT && tries++ < 1) {
+		ret = ceph_monc_do_get_version(&rbdc->client->monc, "osdmap",
+					       &newest_epoch);
+		if (ret < 0)
+			return ret;
+
+		if (rbdc->client->osdc.osdmap->epoch < newest_epoch) {
+			ceph_monc_request_next_osdmap(&rbdc->client->monc);
+			(void) ceph_monc_wait_osdmap(&rbdc->client->monc,
+						     newest_epoch, timeout);
+			goto again;
+		} else {
+			/* the osdmap we have is new enough */
+			return -ENOENT;
+		}
+	}
+
+	return ret;
+}
+
+/*
  * An rbd format 2 image has a unique identifier, distinct from the
  * name given to it by the user.  Internally, that identifier is
  * what's used to specify the names of objects related to the image.
@@ -4739,7 +4912,7 @@ static int rbd_dev_image_id(struct rbd_device *rbd_dev)
 
 		image_id = ceph_extract_encoded_string(&p, p + ret,
 						NULL, GFP_NOIO);
-		ret = IS_ERR(image_id) ? PTR_ERR(image_id) : 0;
+		ret = PTR_ERR_OR_ZERO(image_id);
 		if (!ret)
 			rbd_dev->image_format = 2;
 	} else {
@@ -4860,20 +5033,29 @@ static int rbd_dev_device_setup(struct rbd_device *rbd_dev)
 {
 	int ret;
 
-	/* generate unique id: find highest unique id, add one */
-	rbd_dev_id_get(rbd_dev);
+	/* Get an id and fill in device name. */
+
+	ret = rbd_dev_id_get(rbd_dev);
+	if (ret)
+		return ret;
 
-	/* Fill in the device name, now that we have its id. */
 	BUILD_BUG_ON(DEV_NAME_LEN
 			< sizeof (RBD_DRV_NAME) + MAX_INT_FORMAT_WIDTH);
 	sprintf(rbd_dev->name, "%s%d", RBD_DRV_NAME, rbd_dev->dev_id);
 
-	/* Get our block major device number. */
+	/* Record our major and minor device numbers. */
 
-	ret = register_blkdev(0, rbd_dev->name);
-	if (ret < 0)
-		goto err_out_id;
-	rbd_dev->major = ret;
+	if (!single_major) {
+		ret = register_blkdev(0, rbd_dev->name);
+		if (ret < 0)
+			goto err_out_id;
+
+		rbd_dev->major = ret;
+		rbd_dev->minor = 0;
+	} else {
+		rbd_dev->major = rbd_major;
+		rbd_dev->minor = rbd_dev_id_to_minor(rbd_dev->dev_id);
+	}
 
 	/* Set up the blkdev mapping. */
 
@@ -4885,6 +5067,7 @@ static int rbd_dev_device_setup(struct rbd_device *rbd_dev)
 	if (ret)
 		goto err_out_disk;
 	set_capacity(rbd_dev->disk, rbd_dev->mapping.size / SECTOR_SIZE);
+	set_disk_ro(rbd_dev->disk, rbd_dev->mapping.read_only);
 
 	ret = rbd_bus_add_dev(rbd_dev);
 	if (ret)
@@ -4905,7 +5088,8 @@ err_out_mapping:
 err_out_disk:
 	rbd_free_disk(rbd_dev);
 err_out_blkdev:
-	unregister_blkdev(rbd_dev->major, rbd_dev->name);
+	if (!single_major)
+		unregister_blkdev(rbd_dev->major, rbd_dev->name);
 err_out_id:
 	rbd_dev_id_put(rbd_dev);
 	rbd_dev_mapping_clear(rbd_dev);
@@ -4961,7 +5145,6 @@ static void rbd_dev_image_release(struct rbd_device *rbd_dev)
 static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
 {
 	int ret;
-	int tmp;
 
 	/*
 	 * Get the id from the image id object.  Unless there's an
@@ -4980,7 +5163,7 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
 		goto err_out_format;
 
 	if (mapping) {
-		ret = rbd_dev_header_watch_sync(rbd_dev, true);
+		ret = rbd_dev_header_watch_sync(rbd_dev);
 		if (ret)
 			goto out_header_name;
 	}
@@ -5007,12 +5190,8 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
 err_out_probe:
 	rbd_dev_unprobe(rbd_dev);
 err_out_watch:
-	if (mapping) {
-		tmp = rbd_dev_header_watch_sync(rbd_dev, false);
-		if (tmp)
-			rbd_warn(rbd_dev, "unable to tear down "
-					"watch request (%d)\n", tmp);
-	}
+	if (mapping)
+		rbd_dev_header_unwatch_sync(rbd_dev);
 out_header_name:
 	kfree(rbd_dev->header_name);
 	rbd_dev->header_name = NULL;
@@ -5026,16 +5205,15 @@ err_out_format:
 	return ret;
 }
 
-static ssize_t rbd_add(struct bus_type *bus,
-		       const char *buf,
-		       size_t count)
+static ssize_t do_rbd_add(struct bus_type *bus,
+			  const char *buf,
+			  size_t count)
 {
 	struct rbd_device *rbd_dev = NULL;
 	struct ceph_options *ceph_opts = NULL;
 	struct rbd_options *rbd_opts = NULL;
 	struct rbd_spec *spec = NULL;
 	struct rbd_client *rbdc;
-	struct ceph_osd_client *osdc;
 	bool read_only;
 	int rc = -ENOMEM;
 
@@ -5057,8 +5235,7 @@ static ssize_t rbd_add(struct bus_type *bus,
 	}
 
 	/* pick the pool */
-	osdc = &rbdc->client->osdc;
-	rc = ceph_pg_poolid_by_name(osdc->osdmap, spec->pool_name);
+	rc = rbd_add_get_pool_id(rbdc, spec->pool_name);
 	if (rc < 0)
 		goto err_out_client;
 	spec->pool_id = (u64)rc;
@@ -5090,6 +5267,12 @@ static ssize_t rbd_add(struct bus_type *bus,
 
 	rc = rbd_dev_device_setup(rbd_dev);
 	if (rc) {
+		/*
+		 * rbd_dev_header_unwatch_sync() can't be moved into
+		 * rbd_dev_image_release() without refactoring, see
+		 * commit 1f3ef78861ac.
+		 */
+		rbd_dev_header_unwatch_sync(rbd_dev);
 		rbd_dev_image_release(rbd_dev);
 		goto err_out_module;
 	}
@@ -5110,6 +5293,23 @@ err_out_module:
 	return (ssize_t)rc;
 }
 
+static ssize_t rbd_add(struct bus_type *bus,
+		       const char *buf,
+		       size_t count)
+{
+	if (single_major)
+		return -EINVAL;
+
+	return do_rbd_add(bus, buf, count);
+}
+
+static ssize_t rbd_add_single_major(struct bus_type *bus,
+				    const char *buf,
+				    size_t count)
+{
+	return do_rbd_add(bus, buf, count);
+}
+
 static void rbd_dev_device_release(struct device *dev)
 {
 	struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
@@ -5117,8 +5317,8 @@ static void rbd_dev_device_release(struct device *dev)
 	rbd_free_disk(rbd_dev);
 	clear_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags);
 	rbd_dev_mapping_clear(rbd_dev);
-	unregister_blkdev(rbd_dev->major, rbd_dev->name);
-	rbd_dev->major = 0;
+	if (!single_major)
+		unregister_blkdev(rbd_dev->major, rbd_dev->name);
 	rbd_dev_id_put(rbd_dev);
 	rbd_dev_mapping_clear(rbd_dev);
 }
@@ -5149,9 +5349,9 @@ static void rbd_dev_remove_parent(struct rbd_device *rbd_dev)
 	}
 }
 
-static ssize_t rbd_remove(struct bus_type *bus,
-			  const char *buf,
-			  size_t count)
+static ssize_t do_rbd_remove(struct bus_type *bus,
+			     const char *buf,
+			     size_t count)
 {
 	struct rbd_device *rbd_dev = NULL;
 	struct list_head *tmp;
@@ -5191,16 +5391,14 @@ static ssize_t rbd_remove(struct bus_type *bus,
 	if (ret < 0 || already)
 		return ret;
 
-	ret = rbd_dev_header_watch_sync(rbd_dev, false);
-	if (ret)
-		rbd_warn(rbd_dev, "failed to cancel watch event (%d)\n", ret);
-
+	rbd_dev_header_unwatch_sync(rbd_dev);
 	/*
 	 * flush remaining watch callbacks - these must be complete
 	 * before the osd_client is shutdown
 	 */
 	dout("%s: flushing notifies", __func__);
 	ceph_osdc_flush_notifies(&rbd_dev->rbd_client->client->osdc);
+
 	/*
 	 * Don't free anything from rbd_dev->disk until after all
 	 * notifies are completely processed. Otherwise
@@ -5214,6 +5412,23 @@ static ssize_t rbd_remove(struct bus_type *bus,
 	return count;
 }
 
+static ssize_t rbd_remove(struct bus_type *bus,
+			  const char *buf,
+			  size_t count)
+{
+	if (single_major)
+		return -EINVAL;
+
+	return do_rbd_remove(bus, buf, count);
+}
+
+static ssize_t rbd_remove_single_major(struct bus_type *bus,
+				       const char *buf,
+				       size_t count)
+{
+	return do_rbd_remove(bus, buf, count);
+}
+
 /*
  * create control files in sysfs
  * /sys/bus/rbd/...
@@ -5259,7 +5474,7 @@ static int rbd_slab_init(void)
 
 	rbd_assert(!rbd_segment_name_cache);
 	rbd_segment_name_cache = kmem_cache_create("rbd_segment_name",
-					MAX_OBJ_NAME_SIZE + 1, 1, 0, NULL);
+					CEPH_MAX_OID_NAME_LEN + 1, 1, 0, NULL);
 	if (rbd_segment_name_cache)
 		return 0;
 out_err:
@@ -5295,24 +5510,46 @@ static int __init rbd_init(void)
 
 	if (!libceph_compatible(NULL)) {
 		rbd_warn(NULL, "libceph incompatibility (quitting)");
-
 		return -EINVAL;
 	}
+
 	rc = rbd_slab_init();
 	if (rc)
 		return rc;
+
+	if (single_major) {
+		rbd_major = register_blkdev(0, RBD_DRV_NAME);
+		if (rbd_major < 0) {
+			rc = rbd_major;
+			goto err_out_slab;
+		}
+	}
+
 	rc = rbd_sysfs_init();
 	if (rc)
-		rbd_slab_exit();
+		goto err_out_blkdev;
+
+	if (single_major)
+		pr_info("loaded (major %d)\n", rbd_major);
 	else
-		pr_info("loaded " RBD_DRV_NAME_LONG "\n");
+		pr_info("loaded\n");
+
+	return 0;
 
+err_out_blkdev:
+	if (single_major)
+		unregister_blkdev(rbd_major, RBD_DRV_NAME);
+err_out_slab:
+	rbd_slab_exit();
 	return rc;
 }
 
 static void __exit rbd_exit(void)
 {
+	ida_destroy(&rbd_dev_id_ida);
 	rbd_sysfs_cleanup();
+	if (single_major)
+		unregister_blkdev(rbd_major, RBD_DRV_NAME);
 	rbd_slab_exit();
 }
 
@@ -5322,9 +5559,8 @@ module_exit(rbd_exit);
 MODULE_AUTHOR("Alex Elder <elder@inktank.com>");
 MODULE_AUTHOR("Sage Weil <sage@newdream.net>");
 MODULE_AUTHOR("Yehuda Sadeh <yehuda@hq.newdream.net>");
-MODULE_DESCRIPTION("rados block device");
-
 /* following authorship retained from original osdblk.c */
 MODULE_AUTHOR("Jeff Garzik <jeff@garzik.org>");
 
+MODULE_DESCRIPTION("RADOS Block Device (RBD) driver");
 MODULE_LICENSE("GPL");