Re: block: zero logical block size leads to infinite loop in set_init_blocksize()

[Keith Busch <kbusch@kernel.org>]

On Thu, Sep 03, 2026 at 08:41:24PM +0300, Maks wrote:
> Hi,
> 
> I hit a soft lockup in set_init_blocksize() with a block device whose
> logical_block_size was zero.
> 
> I understand that logical_block_size == 0 violates the block layer
> contract and that the driver which allowed this value needs to be fixed.
> 
> However, the generic block code currently turns this invariant violation
> into a non-terminating loop:
> 
> while (bsize < PAGE_SIZE) {
>     if (size & bsize)
>         break;
>     bsize <<= 1;
> }
> 
> With bsize == 0, the value never changes.

How did you manage to get a block_device created, but bypassed the check
and override for a zero logical block size in blk_validate_limits()? Is
your driver writing over the limits outside the API's update path?