[0/2] blkdev: Fix livelock when loop device updates capacity

Message

Jan Kara Jan. 14, 2019, 8:48 a.m. UTC

Hello,

this series fixes a long standing issue with loop device which can change block
device size under a mounted filesystem which causes infinite loop inside buffer
head code. See patch 2/2 for details about the problem.

Note that generally it is dangerous to resize the loop device when filesystem
is mounted on top of it. However there are some valid use cases for this (such
as growing the loop device and then increasing the filesystem size) so we
cannot just restrict the functionality to exclusive owners of the device.

								Honza

Comments

Jens Axboe Jan. 15, 2019, 2:31 p.m. UTC | #1

On 1/14/19 1:48 AM, Jan Kara wrote:
> Hello,
> 
> this series fixes a long standing issue with loop device which can change block
> device size under a mounted filesystem which causes infinite loop inside buffer
> head code. See patch 2/2 for details about the problem.
> 
> Note that generally it is dangerous to resize the loop device when filesystem
> is mounted on top of it. However there are some valid use cases for this (such
> as growing the loop device and then increasing the filesystem size) so we
> cannot just restrict the functionality to exclusive owners of the device.

That's really a shame...

Anyway, applied for 5.0, thanks Jan.