brd: handle on-demand devices correctly

commit af46566 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 <[email protected]> Cc: Laurent Vivier <[email protected]> Signed-off-by: Jens Axboe <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
ssvb · Jun 3, 2011 · a3a9ec8 · a3a9ec8
1 parent 367ecef
commit a3a9ec8
Showing 1 changed file with 4 additions and 4 deletions.
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
@@ -552,7 +552,7 @@ 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);
 
@@ -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);