2 files changed, 134 insertions, 20 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-rbd b/Documentation/ABI/testing/sysfs-bus-rbd
index 17b119c692da..501adc2a9ec7 100644
--- a/Documentation/ABI/testing/sysfs-bus-rbd
+++ b/Documentation/ABI/testing/sysfs-bus-rbd
@@ -18,6 +18,28 @@ Removal of a device:
 
   $ echo <dev-id> > /sys/bus/rbd/remove
 
+What:           /sys/bus/rbd/add_single_major
+Date:           December 2013
+KernelVersion:  3.14
+Contact:        Sage Weil <sage@inktank.com>
+Description:    Available only if rbd module is inserted with single_major
+                parameter set to true.
+                Usage is the same as for /sys/bus/rbd/add.  If present,
+                should be used instead of the latter: any attempts to use
+                /sys/bus/rbd/add if /sys/bus/rbd/add_single_major is
+                available will fail for backwards compatibility reasons.
+
+What:           /sys/bus/rbd/remove_single_major
+Date:           December 2013
+KernelVersion:  3.14
+Contact:        Sage Weil <sage@inktank.com>
+Description:    Available only if rbd module is inserted with single_major
+                parameter set to true.
+                Usage is the same as for /sys/bus/rbd/remove.  If present,
+                should be used instead of the latter: any attempts to use
+                /sys/bus/rbd/remove if /sys/bus/rbd/remove_single_major is
+                available will fail for backwards compatibility reasons.
+
 Entries under /sys/bus/rbd/devices/<dev-id>/
 --------------------------------------------
 
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 3fa18b0c5e4d..e5ddcb58e9a2 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -91,7 +91,7 @@ static int atomic_dec_return_safe(atomic_t *v)
 
 #define RBD_DRV_NAME "rbd"
 
-#define RBD_MINORS_PER_MAJOR    256             /* max minors per blkdev */
+#define RBD_PART_SHIFT  8
 
 #define RBD_SNAP_DEV_NAME_PREFIX        "snap_"
 #define RBD_MAX_SNAP_NAME_LEN   \
@@ -387,8 +387,17 @@ 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);
@@ -397,21 +406,44 @@ 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_PART_SHIFT;
+}
+
+static int minor_to_rbd_dev_id(int minor)
+{
+        return minor >> RBD_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,
 };
 
 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;
 }
 
@@ -3402,7 +3434,7 @@ 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(1 << RBD_PART_SHIFT);
         if (!disk)
                 return -ENOMEM;
 
@@ -4403,7 +4435,9 @@ static int rbd_dev_id_get(struct rbd_device *rbd_dev)
 {
         int new_dev_id;
 
-        new_dev_id = ida_simple_get(&rbd_dev_id_ida, 0, 0, GFP_KERNEL);
+        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;
 
@@ -4863,13 +4897,19 @@ static int rbd_dev_device_setup(struct rbd_device *rbd_dev)
                         < 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;
-        rbd_dev->minor = 0;
+        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. */
 
@@ -4901,7 +4941,8 @@ 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);
@@ -5022,9 +5063,9 @@ 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;
@@ -5106,6 +5147,23 @@ 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);
@@ -5113,8 +5171,8 @@ 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);
 }
@@ -5145,9 +5203,9 @@ 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;
@@ -5210,6 +5268,23 @@ 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/...
@@ -5298,13 +5373,28 @@ static int __init rbd_init(void)
         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)
-                goto err_out_slab;
+                goto err_out_blkdev;
+
+        if (single_major)
+                pr_info("loaded (major %d)\n", rbd_major);
+        else
+                pr_info("loaded\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;
@@ -5313,6 +5403,8 @@ err_out_slab:
 static void __exit rbd_exit(void)
 {
         rbd_sysfs_cleanup();
+        if (single_major)
+                unregister_blkdev(rbd_major, RBD_DRV_NAME);
         rbd_slab_exit();
 }