rbd: enable extended devt in single-major mode (7e513d43) · Commits · 戴 / test

If single-major device number allocation scheme is turned on, instead of reserving 256 minors per device, which imposes a limit of 4096 images mapped at once, reserve 16 minors per device and enable extended devt feature. This results in a theoretical limit of 65536 images mapped at once, and still allows to have more than 15 partititions: partitions starting with 16th are mapped under major 259 (Block Extended Major): $ rbd showmapped id pool image snap device 0 rbd b5 - /dev/rbd0 # no partitions 1 rbd b2 - /dev/rbd1 # 40 partitions 2 rbd b3 - /dev/rbd2 # 2 partitions $ cat /proc/partitions 251 0 1024 rbd0 251 16 1024 rbd1 251 17 0 rbd1p1 251 18 0 rbd1p2 ... 251 30 0 rbd1p14 251 31 0 rbd1p15 259 0 0 rbd1p16 259 1 0 rbd1p17 ... 259 23 0 rbd1p39 259 24 0 rbd1p40 251 32 1024 rbd2 251 33 0 rbd2p1 251 34 0 rbd2p2 (major 251 was assigned dynamically at module load time) Signed-off-by:

Ilya Dryomov <ilya.dryomov@inktank.com> Reviewed-by:

Josh Durgin <josh.durgin@inktank.com>

drivers/block/rbd.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -91,7 +91,8 @@ static int atomic_dec_return_safe(atomic_t *v)

		#define RBD_DRV_NAME "rbd"

		#define RBD_PART_SHIFT 8
		#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 \
		@@ -415,12 +416,12 @@ 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;
		return dev_id << RBD_SINGLE_MAJOR_PART_SHIFT;
		}

		static int minor_to_rbd_dev_id(int minor)
		{
		return minor >> RBD_PART_SHIFT;
		return minor >> RBD_SINGLE_MAJOR_PART_SHIFT;
		}

		static BUS_ATTR(add, S_IWUSR, NULL, rbd_add);
		@@ -3434,7 +3435,9 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
		u64 segment_size;

		/* create gendisk info */
		disk = alloc_disk(1 << RBD_PART_SHIFT);
		disk = alloc_disk(single_major ?
		(1 << RBD_SINGLE_MAJOR_PART_SHIFT) :
		RBD_MINORS_PER_MAJOR);
		if (!disk)
		return -ENOMEM;

		@@ -3442,6 +3445,8 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
		rbd_dev->dev_id);
		disk->major = rbd_dev->major;
		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;

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