Re: [PATCH v3 2/2] exfat: EXFAT_IOC_GET_VALID_DATA ioctl

[David Timber]

On 3/13/26 00:06, Darrick J. Wong wrote:
> /me wonders if the problem here is that the "unwritten" post-VDL range
> is worse than a regular unwritten range in the sense that you have to
> write zeroes to all the space between the VDL and wherever your write()
> starts, e.g. if the VDL is set to 1G and I pwrite a single byte at 8GB,
> that turns into a 7-billion-x write amplification.
Yes. That's the problem being addressed here.

Again, imho, VDL is NOT a hole. It should be treated differently. VDL is
not required to be aligned to the block/extent/cluster size(holes in
sparse files tend to be albeit not a requirement). You can't punch or
dig holes in exFAT. Using SEEK_*HOLE* to find *VDL* doesn't make any
sense(to me, at least).

thb, I don't really care if the ioctl patch is accepted or not. If
SEEK_HOLE/SEEK_DATA is really what maintainers see fit despite these
deviations, I'd have to honour that decision and bring iomap to exFAT, I
guess. That'd be a lot of work though because it mean will the rework of
the entire exFAT code base. Not saying exFAT doesn't deserve iomap but
that might be a little over my paygrade since there are thousands of
embedded devices already using in-kernel exFAT.

I retract the patches regarding the ioctl. For the time being, the focus
should be on making exFAT and NTFS useable and stable before introducing
ioctls. Sorry for my poor judgement.

Davo