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    Subject[136/146] brd: handle on-demand devices correctly
    2.6.38-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Namhyung Kim <namhyung@gmail.com>

    commit af46566885a373b0a526932484cd8fef8de7b598 upstream.

    When finding or allocating a ram disk device, brd_probe() did not take
    partition numbers into account so that it can result to a different
    device. Consider following example (I set CONFIG_BLK_DEV_RAM_COUNT=4
    for simplicity) :

    $ sudo modprobe brd max_part=15
    $ ls -l /dev/ram*
    brw-rw---- 1 root disk 1, 0 2011-05-25 15:41 /dev/ram0
    brw-rw---- 1 root disk 1, 16 2011-05-25 15:41 /dev/ram1
    brw-rw---- 1 root disk 1, 32 2011-05-25 15:41 /dev/ram2
    brw-rw---- 1 root disk 1, 48 2011-05-25 15:41 /dev/ram3
    $ sudo mknod /dev/ram4 b 1 64
    $ sudo dd if=/dev/zero of=/dev/ram4 bs=4k count=256
    256+0 records in
    256+0 records out
    1048576 bytes (1.0 MB) copied, 0.00215578 s, 486 MB/s
    namhyung@leonhard:linux$ ls -l /dev/ram*
    brw-rw---- 1 root disk 1, 0 2011-05-25 15:41 /dev/ram0
    brw-rw---- 1 root disk 1, 16 2011-05-25 15:41 /dev/ram1
    brw-rw---- 1 root disk 1, 32 2011-05-25 15:41 /dev/ram2
    brw-rw---- 1 root disk 1, 48 2011-05-25 15:41 /dev/ram3
    brw-r--r-- 1 root root 1, 64 2011-05-25 15:45 /dev/ram4
    brw-rw---- 1 root disk 1, 1024 2011-05-25 15:44 /dev/ram64

    After this patch, /dev/ram4 - instead of /dev/ram64 - was
    accessed correctly.

    In addition, 'range' passed to blk_register_region() should
    include all range of dev_t that RAMDISK_MAJOR can address.
    It does not need to be limited by partition numbers unless
    'rd_nr' param was specified.

    Signed-off-by: Namhyung Kim <namhyung@gmail.com>
    Cc: Laurent Vivier <Laurent.Vivier@bull.net>
    Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/block/brd.c | 8 ++++----
    1 file changed, 4 insertions(+), 4 deletions(-)

    --- a/drivers/block/brd.c
    +++ b/drivers/block/brd.c
    @@ -552,7 +552,7 @@ static struct kobject *brd_probe(dev_t d
    struct kobject *kobj;

    mutex_lock(&brd_devices_mutex);
    - brd = brd_init_one(dev & MINORMASK);
    + brd = brd_init_one(MINOR(dev) >> part_shift);
    kobj = brd ? get_disk(brd->brd_disk) : ERR_PTR(-ENOMEM);
    mutex_unlock(&brd_devices_mutex);

    @@ -593,10 +593,10 @@ static int __init brd_init(void)

    if (rd_nr) {
    nr = rd_nr;
    - range = rd_nr;
    + range = rd_nr << part_shift;
    } else {
    nr = CONFIG_BLK_DEV_RAM_COUNT;
    - range = 1UL << (MINORBITS - part_shift);
    + range = 1UL << MINORBITS;
    }

    if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
    @@ -635,7 +635,7 @@ static void __exit brd_exit(void)
    unsigned long range;
    struct brd_device *brd, *next;

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

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



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