Can fallocate() ops be emulated better using SMB request compounding?

[Jeremy Allison]

On Thu, Dec 07, 2023 at 05:50:50PM +0000, David Howells wrote:
>Jeremy Allison <jra at samba.org> wrote:
>
>> >Further, are the two ops then essentially done atomically?
>>
>> No. They are processed (at least in Samba) as two separate
>> requests and can be raced by local or other remote access.
>
>So just compounding them would leave us in the same situation we are in now -
>which would be fine.
>
>What do you think about the idea of having the server see a specifically
>arranged compounded pair and turn them into an op that can't otherwise be
>represented in the protocol?

Complex, ugly code. How long does the server wait
for the second operation before proceeding with
the first ?

>Or is it better to try and get the protocol extended?

If this is a Linux -> Linux op, we have a protocol
space (the SMB3+POSIX) we can extend without having
to go via Microsoft. But this would need to be very carefully designed.