Re: [PATCH] Modify RAMDISK (brd) device to be able to manage partitions
From: Nick Piggin
Date: Thu Apr 03 2008 - 08:24:00 EST
On Thursday 03 April 2008 22:44, Laurent Vivier wrote:
> This patch adds partition management for Block RAM Device (BRD).
>
> This patch is done to keep in sync BRD and loop device drivers.
Hi Laurent,
Thanks very much for this. I will ensure Andrew gets this.
Nick
>
> 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 <Laurent.Vivier@xxxxxxxx>
> ---
> 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);
--
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