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brd: handle on-demand devices correctly 

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>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Namhyung Kim 2011-05-26 21:06:50 +02:00 committed by Jens Axboe
parent 315980c868
commit af46566885
1 changed files with 4 additions and 4 deletions
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8
drivers/block/brd.c
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@ -548,7 +548,7 @@ static struct kobject *brd_probe(dev_t dev, int *part, void *data)
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);
@ -589,10 +589,10 @@ 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"))
@ -631,7 +631,7 @@ 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);