linux-kernel - Re: [RFC PATCH] ceph: initialize superblock s_time

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Date:   Thu, 27 Jun 2019 12:10:25 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Sage Weil <sweil@...hat.com>
Cc:     Luis Henriques <lhenriques@...e.com>,
        "Yan, Zheng" <zyan@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
        ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] ceph: initialize superblock s_time_gran to 1

On Thu, 2019-06-27 at 15:44 +0000, Sage Weil wrote:
> On Thu, 27 Jun 2019, Jeff Layton wrote:
> > On Thu, 2019-06-27 at 14:51 +0100, Luis Henriques wrote:
> > > Having granularity set to 1us results in having inode timestamps with a
> > > accurancy different from the fuse client (i.e. atime, ctime and mtime will
> > > always end with '000').  This patch normalizes this behaviour and sets the
> > > granularity to 1.
> > > 
> > > Signed-off-by: Luis Henriques <lhenriques@...e.com>
> > > ---
> > >  fs/ceph/super.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > Hi!
> > > 
> > > As far as I could see there are no other side-effects of changing
> > > s_time_gran but I'm really not sure why it was initially set to 1000 in
> > > the first place so I may be missing something.
> > > 
> > > diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> > > index d57fa60dcd43..35dd75bc9cd0 100644
> > > --- a/fs/ceph/super.c
> > > +++ b/fs/ceph/super.c
> > > @@ -980,7 +980,7 @@ static int ceph_set_super(struct super_block *s, void *data)
> > >     s->s_d_op = &ceph_dentry_ops;
> > >     s->s_export_op = &ceph_export_ops;
> > >  
> > > -   s->s_time_gran = 1000;  /* 1000 ns == 1 us */
> > > +   s->s_time_gran = 1;
> > >  
> > >     ret = set_anon_super(s, NULL);  /* what is that second arg for? */
> > >     if (ret != 0)
> > 
> > 
> > Looks like it was set that way since the client code was originally
> > merged. Was this an earlier limitation of ceph that is no longer
> > applicable?
> > 
> > In any case, I see no need at all to keep this at 1000, so:
> 
> As long as the encoded on-write time value is at ns resolution, I 
> agree!  No recollection of why I did this :(
> 
> Reviewed-by: Sage Weil <sage@...hat.com>

Good enough for me. I went ahead and merged this into the testing
branch. Assuming nothing breaks, this should make v5.3.

Thanks,
-- 
Jeff Layton <jlayton@...nel.org>