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    SubjectRe: [PATCH] Modify loop device to be able to manage partitions of the disk image
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    On Thursday 06 March 2008 20:43, Laurent Vivier wrote:
    > This patch allows to use loop device with partitionned disk image.
    >
    > Original behavior of loop is not modified.
    >
    > A new parameter is introduced to define how many partition we want to be
    > able to manage per loop device. This parameter is "max_part".
    >
    > For instance, to manage 63 partitions / loop device, we will do:
    > # modprobe max_part=63
    > # ls -l /dev/loop?*
    > brw-rw---- 1 root disk 7, 0 2008-03-05 14:55 /dev/loop0
    > brw-rw---- 1 root disk 7, 64 2008-03-05 14:55 /dev/loop1
    > brw-rw---- 1 root disk 7, 128 2008-03-05 14:55 /dev/loop2
    > brw-rw---- 1 root disk 7, 192 2008-03-05 14:55 /dev/loop3
    > brw-rw---- 1 root disk 7, 256 2008-03-05 14:55 /dev/loop4
    > brw-rw---- 1 root disk 7, 320 2008-03-05 14:55 /dev/loop5
    > brw-rw---- 1 root disk 7, 384 2008-03-05 14:55 /dev/loop6
    > brw-rw---- 1 root disk 7, 448 2008-03-05 14:55 /dev/loop7
    >
    > And to attach a raw partitionned disk image, the original losetup is used:
    >
    > # losetup -f etch.img
    > # ls -l /dev/loop?*
    > brw-rw---- 1 root disk 7, 0 2008-03-05 14:55 /dev/loop0
    > brw-rw---- 1 root disk 7, 1 2008-03-05 14:57 /dev/loop0p1
    > brw-rw---- 1 root disk 7, 2 2008-03-05 14:57 /dev/loop0p2
    > brw-rw---- 1 root disk 7, 5 2008-03-05 14:57 /dev/loop0p5
    > brw-rw---- 1 root disk 7, 64 2008-03-05 14:55 /dev/loop1
    > brw-rw---- 1 root disk 7, 128 2008-03-05 14:55 /dev/loop2
    > brw-rw---- 1 root disk 7, 192 2008-03-05 14:55 /dev/loop3
    > brw-rw---- 1 root disk 7, 256 2008-03-05 14:55 /dev/loop4
    > brw-rw---- 1 root disk 7, 320 2008-03-05 14:55 /dev/loop5
    > brw-rw---- 1 root disk 7, 384 2008-03-05 14:55 /dev/loop6
    > brw-rw---- 1 root disk 7, 448 2008-03-05 14:55 /dev/loop7
    > # mount /dev/loop0p1 /mnt
    > # ls /mnt
    > bench cdrom home lib mnt root srv usr
    > bin dev initrd lost+found opt sbin sys var
    > boot etc initrd.img media proc selinux tmp vmlinuz
    > # umount /mnt
    > # losetup -d /dev/loop0
    >
    > Of course, the same behavior can be done using kpartx on a loop device,
    > but modifying loop avoids to stack several layers of block device (loop +
    > device mapper), this is a very light modification (40% of modifications
    > are to manage the new parameter). Moreover all partition tables known
    > by the kernel are managed (kpartx implements only a subset).

    Do you think we do something similar for drivers/block/brd.c too? I'd
    like to try to maintain parity between them where possible...



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