On Thu, Oct 29, 2020 at 07:51:49AM +0000, Christoph Hellwig wrote:

On Wed, Oct 28, 2020 at 03:24:34PM +0800, Ming Lei wrote:

quoted

Mounted NBD device can be resized, one use case is rbd-nbd.

Fix the issue by setting up default block size, then not touch it
in nbd_size_update() any more. This kind of usage is aligned with loop
which has same use case too.

I think the only reasonable fix here is to remove the set_blocksize
call entirely.  The concept of block size set by it is a file system
construct and nbd has not business setting it at all.

I think the idea is reasonable, we have several drivers(loop, nbd, zram,
pktcdvd, bcache) which call into set_blocksize().

Also ioctl(BLKBSZSET) which is used by 'blockdev --setbsz', still not
understand which kind of use case is served for.


Thanks,
Ming