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

[Al Viro]

On Tue, Aug 29, 2023 at 08:43:31PM -0400, Jeff Layton wrote:
> On Wed, 2023-08-30 at 01:02 +0100, Al Viro wrote:
> > 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.
> 
> The only problem with this plan is that Linus has already merged this.
> I've no issue with adding the request_mask to the kstat and removing it
> as a separate parameter elsewhere, but I think we'll need to do it on
> top of what's already been merged.

D'oh...  My apologies; I'll do a branch on top of that (and rebase on
top of -rc1 once the window closes).