Re: [PATCH v3 00/13] fiemap extension for more physical information

[Gao Xiang]

Hi,

On 2024/4/3 15:22, Sweet Tea Dorminy wrote:
> For many years, various btrfs users have written programs to discover
> the actual disk space used by files, using root-only interfaces.
> However, this information is a great fit for fiemap: it is inherently
> tied to extent information, all filesystems can use it, and the
> capabilities required for FIEMAP make sense for this additional
> information also.
>
> Hence, this patchset adds various additional information to fiemap,
> and extends filesystems (but not iomap) to return it.  This uses some of
> the reserved padding in the fiemap extent structure, so programs unaware
> of the changes will be unaffected.

I'm not sure why here iomap was excluded technically or I'm missing some
previous comments?

> This is based on next-20240403. I've tested the btrfs part of this with
> the standard btrfs testing matrix locally and manually, and done minimal
> testing of the non-btrfs parts.
>
> I'm unsure whether btrfs should be returning the entire physical extent
> referenced by a particular logical range, or just the part of the
> physical extent referenced by that range. The v2 thread has a discussion
> of this.

Could you also make iomap support new FIEMAP physical extent information?
since compressed EROFS uses iomap FIEMAP interface to report compressed
extents ("z_erofs_iomap_report_ops") but there is no way to return
correct compressed lengths, that is unexpected.

Thanks,
Gao Xiang