Re: [PATCH v8 02/12] fs: add infrastructure for multigrain timestamps

[Jeff Layton]

On Wed, 2024-10-02 at 11:14 +0200, Jan Kara wrote:
> On Tue 01-10-24 09:34:18, Jeff Layton wrote:
> > On Tue, 2024-10-01 at 15:20 +0200, Jan Kara wrote:
> > > > diff --git a/fs/stat.c b/fs/stat.c
> > > > index 41e598376d7e..381926fb405f 100644
> > > > --- a/fs/stat.c
> > > > +++ b/fs/stat.c
> > > > @@ -26,6 +26,35 @@
> > > >  #include "internal.h"
> > > >  #include "mount.h"
> > > >  
> > > > +/**
> > > > + * fill_mg_cmtime - Fill in the mtime and ctime and flag ctime as QUERIED
> > > > + * @stat: where to store the resulting values
> > > > + * @request_mask: STATX_* values requested
> > > > + * @inode: inode from which to grab the c/mtime
> > > > + *
> > > > + * Given @inode, grab the ctime and mtime out if it and store the result
> > > 						 ^^ of
> > > 
> > > > + * in @stat. When fetching the value, flag it as QUERIED (if not already)
> > > > + * so the next write will record a distinct timestamp.
> > > > + */
> > > > +void fill_mg_cmtime(struct kstat *stat, u32 request_mask, struct inode *inode)
> > > > +{
> > > 
> > > Given how things worked out in the end, it seems this function doesn't need
> > > to handle mtime at all and we can move mtime handling back to shared generic
> > > code?
> > > 
> > 
> > I don't think we can. The mtime is effectively derived from the ctime.
> > 
> > If I query only the mtime, I think it's reasonable to expect that it
> > will change if there is another write, even if I don't query the ctime.
> > We won't get that unless we can also set the flag in the ctime when
> > only the mtime is requested.
> 
> Aha, right. I already forgot about this :). Can you please add to the
> comment the above explanation so that we remember next time somebody wants
> to "clean this up" like me ;)? Thanks!
> 
> Also feel free to add:
> 
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> 
> 								Honza

Done, and the revised version is in my tree.

Thanks for the review!
-- 
Jeff Layton <jlayton@xxxxxxxxxx>