Re: [PATCH V3] block: loop:use kstatfs.f_bsize of backing file to set discard granularity

[Ming Lei <ming.lei@redhat.com>]

On Wed, Jan 26, 2022 at 11:58:30AM +0800, Ming Lei wrote:
> If backing file's filesystem has implemented ->fallocate(), we think the
> loop device can support discard, then pass sb->s_blocksize as
> discard_granularity. However, some underlying FS, such as overlayfs,
> doesn't set sb->s_blocksize, and causes discard_granularity to be set as
> zero, then the warning in __blkdev_issue_discard() is triggered.
> 
> Christoph suggested to pass kstatfs.f_bsize as discard granularity, and
> this way is fine because kstatfs.f_bsize means 'Optimal transfer block
> size', which still matches with definition of discard granularity.
> 
> So fix the issue by setting discard_granularity as kstatfs.f_bsize if it
> is available, otherwise claims discard isn't supported.
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Vivek Goyal <vgoyal@redhat.com>
> Reported-by: Pei Zhang <pezhang@redhat.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> V3:
> 	- following Christoph's suggestion to not claim discard support if
> 	vfs_statfs() fails 

Hi Jens,

Any chance to merge it to v5.17?


Thanks,
Ming