Re: [PATCH 10/21] block: Add fops atomic write support

Bart Van Assche
2023-10-06T17:22:17Z

On 10/5/23 21:31, Dave Chinner wrote:
> Then I don't see what your concern is.
>
> Single sector writes are guaranteed atomic and have been for as long
> as I've worked in this game. OTOH, multi-sector writes are not
> guaranteed to be atomic - they can get torn on sector boundaries, but
> the individual sectors within that write are guaranteed to be
> all-or-nothing.
>
> Any hardware device that does not guarantee single sector write
> atomicity (i.e. tears in the middle of a sector) is, by definition,
> broken. And we all know that broken hardware means nothing in the
> storage stack works as it should, so I just don't see what point you
> are trying to make...

Do you agree that the above implies that it is not useful in patch 01/21
of this series to track atomic_write_unit_min_bytes in the block layer
nor to export this information to user space? The above implies that
this parameter will always be equal to the logical block size. Writes to
a single physical block happen atomically. If there are multiple logical
blocks per physical block, the block device must serialize
read/modify/write cycles internally.

Thanks,

Bart.