Commit 541c742a authored Feb 21, 2013 by Guo Chao Committed by Jens Axboe Feb 22, 2013

loopdev: update block device size in loop_set_status()



Loop device driver sometimes fails to impose the size limit on the
device. Keep issuing following two commands:

losetup --offset 7517244416 --sizelimit 3224971264 /dev/loop0 backed_file
blockdev --getsize64 /dev/loop0

blockdev reports file size instead of sizelimit several out of 100 times.

The problems are:

	- losetup set up the device in two ioctl:
		  LOOP_SET_FD and LOOP_SET_STATUS64.

	- LOOP_SET_STATUS64 only update size of gendisk.

Block device size will be updated lazily when device comes to use. If udev
rushes in between the two ioctl, it will bring in a block device whose
size is backing file size. If the device is not released after
LOOP_SET_STATUS64 ioctl, blockdev will not see the updated size.

Update block size in LOOP_SET_STATUS64 ioctl.

Signed-off-by: Guo Chao <yan@linux.vnet.ibm.com>
Reported-by: M. Hindess <hindessm@uk.ibm.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Guo Chao <yan@linux.vnet.ibm.com>
Cc: Nikanth Karthikesan <knikanth@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 5370019d

drivers/block/loop.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -1092,8 +1092,13 @@ loop_set_status(struct loop_device lo, const struct loop_info64 info)

		if (lo->lo_offset != info->lo_offset \|\|
		lo->lo_sizelimit != info->lo_sizelimit) {
		struct block_device *bdev = lo->lo_device;

		if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit))
		return -EFBIG;

		bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
		kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
		}
		loop_config_discard(lo);

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