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

Bart Van Assche
2023-10-05T17:18:37Z

On 10/4/23 11:17, Martin K. Petersen wrote:
>
> Hi Bart!
>
>> In other words, also for the above example it is guaranteed that
>> writes of a single logical block (512 bytes) are atomic, no matter
>> what value is reported as the ATOMIC TRANSFER LENGTH GRANULARITY.
>
> There is no formal guarantee that a disk drive sector
> read-modify-write operation results in a readable sector after a
> power failure. We have definitely seen blocks being mangled in the
> field.

Aren't block devices expected to use a capacitor that provides enough
power to handle power failures cleanly?

How about blacklisting block devices that mangle blocks if a power
failure occurs? I think such block devices are not compatible with
journaling filesystems nor with log-structured filesystems.

Thanks,

Bart.