Re: [PATCH v6 1/7] fs: pass the request_mask to generic_fillattr

Al Viro
2023-08-30T00:04:20Z

On Tue, Aug 29, 2023 at 06:58:47PM -0400, Jeff Layton wrote:
> On Tue, 2023-08-29 at 23:44 +0100, Al Viro wrote:
> > On Tue, Jul 25, 2023 at 10:58:14AM -0400, Jeff Layton wrote:
> > > generic_fillattr just fills in the entire stat struct indiscriminately
> > > today, copying data from the inode. There is at least one attribute
> > > (STATX_CHANGE_COOKIE) that can have side effects when it is reported,
> > > and we're looking at adding more with the addition of multigrain
> > > timestamps.
> > >
> > > Add a request_mask argument to generic_fillattr and have most callers
> > > just pass in the value that is passed to getattr. Have other callers
> > > (e.g. ksmbd) just pass in STATX_BASIC_STATS. Also move the setting of
> > > STATX_CHANGE_COOKIE into generic_fillattr.
> >
> > Out of curiosity - how much PITA would it be to put request_mask into
> > kstat? Set it in vfs_getattr_nosec() (and those get_file_..._info()
> > on smbd side) and don't bother with that kind of propagation boilerplate
> > - just have generic_fillattr() pick it there...
> >
> > Reduces the patchset size quite a bit...
>
> It could be done. To do that right, I think we'd want to drop
> request_mask from the ->getattr prototype as well and just have
> everything use the mask in the kstat.
>
> I don't think it'd reduce the size of the patchset in any meaningful
> way, but it might make for a more sensible API over the long haul.

->getattr() prototype change would be decoupled from that - for your
patchset you'd only need the field addition + setting in vfs_getattr_nosec()
(and possibly in ksmbd), with the remainders of both series being
independent from each other.

What I suggest is

branchpoint -> field addition (trivial commit) -> argument removal
|
V
your series, starting with "use stat->request_mask in generic_fillattr()"

Total size would be about the same, but it would be easier to follow
the less trivial part of that. Nothing in your branch downstream of
that touches any ->getattr() instances, so it should have no
conflicts with the argument removal side of things.