Re: [PATCH] block: Return the soft block size for compat BLKBSZGET

[Arnd Bergmann]

On Fri, Oct 23, 2026, at 17:36, Hungyu Lin wrote:
> BLKBSZGET returns the block device's soft block size, while BLKSSZGET
> returns its logical sector size. The compat BLKBSZGET_32 handler uses
> bdev_logical_block_size(), so it returns the wrong value when these
> sizes differ.
>
> For example, on an x86_64 kernel a native query of a RAM or loop device
> with 512-byte logical sectors returns the initial soft block size of
> 4096 bytes, but an i386 process gets 512 bytes. This makes 32-bit
> blockdev --getbsz and the BSZ column of --report disagree with native
> queries, even without a preceding BLKBSZSET.
>
> Use block_size() as the native handler and the pre-regression compat
> handler do, and correct the case comment to describe the soft size.
>
> Fixes: 9b81648cb5e3 ("compat_ioctl: simplify up block/ioctl.c")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Hungyu Lin <dennylin0707@xxxxxxxxx>

Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>