This patch adds partition management for Block RAM Device (BRD).

This patch is done to keep in sync BRD and loop device drivers.

This patch adds a parameter to the module, max_part, to specify
the maximum number of partitions per RAM device.

Example:

# modprobe brd max_part=63
# ls -l /dev/ram*
brw-rw---- 1 root disk 1, 0 2008-04-03 13:39 /dev/ram0
brw-rw---- 1 root disk 1, 64 2008-04-03 13:39 /dev/ram1
brw-rw---- 1 root disk 1, 640 2008-04-03 13:39 /dev/ram10
brw-rw---- 1 root disk 1, 704 2008-04-03 13:39 /dev/ram11
brw-rw---- 1 root disk 1, 768 2008-04-03 13:39 /dev/ram12
brw-rw---- 1 root disk 1, 832 2008-04-03 13:39 /dev/ram13
brw-rw---- 1 root disk 1, 896 2008-04-03 13:39 /dev/ram14
brw-rw---- 1 root disk 1, 960 2008-04-03 13:39 /dev/ram15
brw-rw---- 1 root disk 1, 128 2008-04-03 13:39 /dev/ram2
brw-rw---- 1 root disk 1, 192 2008-04-03 13:39 /dev/ram3
brw-rw---- 1 root disk 1, 256 2008-04-03 13:39 /dev/ram4
brw-rw---- 1 root disk 1, 320 2008-04-03 13:39 /dev/ram5
brw-rw---- 1 root disk 1, 384 2008-04-03 13:39 /dev/ram6
brw-rw---- 1 root disk 1, 448 2008-04-03 13:39 /dev/ram7
brw-rw---- 1 root disk 1, 512 2008-04-03 13:39 /dev/ram8
brw-rw---- 1 root disk 1, 576 2008-04-03 13:39 /dev/ram9
# fdisk /dev/ram0
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): o
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-2, default 1): 1
Last cylinder or +size or +sizeM or +sizeK (1-2, default 2): 2

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
# ls -l /dev/ram0*
brw-rw---- 1 root disk 1, 0 2008-04-03 13:40 /dev/ram0
brw-rw---- 1 root disk 1, 1 2008-04-03 13:40 /dev/ram0p1
# mkfs /dev/ram0p1
mke2fs 1.40-WIP (14-Nov-2006)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
4016 inodes, 16032 blocks
801 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=16515072
2 block groups
8192 blocks per group, 8192 fragments per group
2008 inodes per group
Superblock backups stored on blocks:
8193

Writing inode tables: done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 26 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
# mount /dev/ram0p1 /mnt
df /mnt
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/ram0p1 15521 138 14582 1% /mnt
# ls -l /mnt
total 12
drwx------ 2 root root 12288 2008-04-03 13:41 lost+found
# umount /mnt
# rmmod brd

Signed-off-by: Laurent Vivier
---
drivers/block/brd.c | 19 ++++++++++++++-----
1 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 8536480..8baf781 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -386,10 +386,14 @@ static struct block_device_operations brd_fops = {
*/
static int rd_nr;
int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
+static int max_part;
+static int part_shift;
module_param(rd_nr, int, 0);
MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
module_param(rd_size, int, 0);
MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
+module_param(max_part, int, 0);
+MODULE_PARM_DESC(max_part, "Maximum number of partitions per RAM disk");
MODULE_LICENSE("GPL");
MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);

@@ -434,11 +438,11 @@ static struct brd_device *brd_alloc(int i)
blk_queue_max_sectors(brd->brd_queue, 1024);
blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);

- disk = brd->brd_disk = alloc_disk(1);
+ disk = brd->brd_disk = alloc_disk(1 << part_shift);
if (!disk)
goto out_free_queue;
disk->major = RAMDISK_MAJOR;
- disk->first_minor = i;
+ disk->first_minor = i << part_shift;
disk->fops = &brd_fops;
disk->private_data = brd;
disk->queue = brd->brd_queue;
@@ -522,7 +526,12 @@ static int __init brd_init(void)
* themselves and have kernel automatically instantiate actual
* device on-demand.
*/
- if (rd_nr > 1UL << MINORBITS)
+
+ part_shift = 0;
+ if (max_part > 0)
+ part_shift = fls(max_part);
+
+ if (rd_nr > 1UL << (MINORBITS - part_shift))
return -EINVAL;

if (rd_nr) {
@@ -530,7 +539,7 @@ static int __init brd_init(void)
range = rd_nr;
} else {
nr = CONFIG_BLK_DEV_RAM_COUNT;
- range = 1UL << MINORBITS;
+ range = 1UL << (MINORBITS - part_shift);
}

if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
@@ -569,7 +578,7 @@ static void __exit brd_exit(void)
unsigned long range;
struct brd_device *brd, *next;

- range = rd_nr ? rd_nr : 1UL << MINORBITS;
+ range = rd_nr ? rd_nr : 1UL << (MINORBITS - part_shift);

list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
brd_del_one(brd);
--
1.5.2.4

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