Re: [PATCH 2/2] xfs: expose the current zonegc required status in sysfs

[Niklas Cassel <cassel@kernel.org>]

On Wed, Apr 22, 2026 at 08:04:17AM +0200, Christoph Hellwig wrote:
> On Mon, Apr 20, 2026 at 03:50:14PM +0200, Niklas Cassel wrote:
> > The current zonegc required status is currently available in
> > /proc/<pid>/mountstats (which contains stats for all mounted zoned XFS
> > filesystems), under "RT GC required:".
> > 
> > Add a sysfs attribute /sys/fs/xfs/<dev>/zoned/zonegc_required for the same.
> > This makes it trivial for monitoring software to read the value, for a
> > specific filesystem, without any complex parsing.
> 
> GC needed is a very complex internal condition, and I don't think
> exposing the current value as a stable ABI is a good idea.

So we have the following options:
1) /sys/fs/xfs/<dev>/zoned/
2) /sys/fs/xfs/<dev>/stats/stats
3) /sys/kernel/debug/xfs/<dev>/


In my mind, debugfs is usually used for sensitive stuff, however, considering
that the information exposed in this patch is exactly the same information as
"GC required:" in /proc/<pid>/mountstats, I assume that the sensitive
argument is not really applicable here.


Like you say, debugfs can also be used in order to avoid exposing the current
value as a stable ABI. However, since the information exposed in this patch
is accessed using the exact same function call: xfs_zoned_need_gc() as
"GC required:" in /proc/<pid>/mountstats, isn't the current value already
exposed as a stable ABI?


Or perhaps I am missing something here, and for some reason, unlike a sysfs
attribute, the information exposed in /proc/<pid>/mountstats is not considered
a stable ABI ?


That said, if you prefer 2) or 3) over 1) for exposing zonegc_required,
please tell me which you prefer, and I can send a V2 with that.


Kind regards,
Niklas