On Tue, Mar 04, 2025 at 05:53:01PM -0800, Luis Chamberlain wrote:
> The commit titled "block/bdev: lift block size restrictions to 64k"
> lifted the block layer's max supported block size to 64k inside the
> helper blk_validate_block_size() now that we support large folios.
> However in lifting the block size we also removed the silly use
> cases many filesystems have to use sb_set_blocksize() to *verify*
> that the block size < PAGE_SIZE. The call to sb_set_blocksize() can
> happen in-kernel given mkfs utilities *can* create for example an
> ext4 32k block size filesystem on x86_64, the issue we want to prevent
> is mounting it on x86_64 unless the filesystem supports LBS.
>
> While, we could argue that such checks should be filesystem specific,
> there are much more users of sb_set_blocksize() than LBS enabled
> filesystem on linux-next, so just do the easier thing and bring back
> the PAGE_SIZE check for sb_set_blocksize() users.
>
> This will ensure that tests such as generic/466 when run in a loop
> against say, ext4, won't try to try to actually mount a filesystem with
> a block size larger than your filesystem supports given your PAGE_SIZE
> and in the worst case crash.
>
> Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
bcachefs doesn't use sb_set_blocksize() - but it appears it should, and
it does also support bs > ps in -next.
Can we get a proper helper for lbs filesystems?
> ---
>
> Christian, a small fixup for a crash when running generic/466 on ext4
> in a loop. The issue is obvious, and we just need to ensure we don't
> break old filesystem expectations of sb_set_blocksize().
>
> This still allows XFS with 32k block size and I even tested with XFS
> with 32k block size and a 32k sector size set.
>
> block/bdev.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/bdev.c b/block/bdev.c
> index 3bd948e6438d..de9ebc3e5d15 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -181,7 +181,7 @@ EXPORT_SYMBOL(set_blocksize);
>
> int sb_set_blocksize(struct super_block *sb, int size)
> {
> - if (set_blocksize(sb->s_bdev_file, size))
> + if (size > PAGE_SIZE || set_blocksize(sb->s_bdev_file, size))
> return 0;
> /* If we get here, we know size is validated */
> sb->s_blocksize = size;
> --
> 2.47.2
>
