linux-kernel - Re: [PATCH 15/79] bfs: switch to new ctime accessors

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Date:   Thu, 22 Jun 2023 14:30:50 +0200
From:   Jan Kara <jack@...e.cz>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Jan Kara <jack@...e.cz>, Christian Brauner <brauner@...nel.org>,
        "Tigran A. Aivazian" <aivazian.tigran@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/79] bfs: switch to new ctime accessors

On Wed 21-06-23 12:57:19, Jeff Layton wrote:
> On Wed, 2023-06-21 at 18:48 +0200, Jan Kara wrote:
> > On Wed 21-06-23 10:45:28, Jeff Layton wrote:
> > > In later patches, we're going to change how the ctime.tv_nsec field is
> > > utilized. Switch to using accessor functions instead of raw accesses of
> > > inode->i_ctime.
> > > 
> > > Signed-off-by: Jeff Layton <jlayton@...nel.org>
> > 
> > ...
> > 
> > > diff --git a/fs/bfs/inode.c b/fs/bfs/inode.c
> > > index 1926bec2c850..c964316be32b 100644
> > > --- a/fs/bfs/inode.c
> > > +++ b/fs/bfs/inode.c
> > > @@ -82,10 +82,10 @@ struct inode *bfs_iget(struct super_block *sb, unsigned long ino)
> > >  	inode->i_blocks = BFS_FILEBLOCKS(di);
> > >  	inode->i_atime.tv_sec =  le32_to_cpu(di->i_atime);
> > >  	inode->i_mtime.tv_sec =  le32_to_cpu(di->i_mtime);
> > > -	inode->i_ctime.tv_sec =  le32_to_cpu(di->i_ctime);
> > > +	inode_ctime_set_sec(inode, le32_to_cpu(di->i_ctime));
> > >  	inode->i_atime.tv_nsec = 0;
> > >  	inode->i_mtime.tv_nsec = 0;
> > > -	inode->i_ctime.tv_nsec = 0;
> > > +	inode_ctime_set_nsec(inode, 0);
> > 
> > So I'm somewhat wondering here - in other filesystem you construct
> > timespec64 and then use inode_ctime_set(). Here you use
> > inode_ctime_set_sec() + inode_ctime_set_nsec(). What's the benefit? It
> > seems these two functions are not used that much some maybe we could just
> > live with just inode_ctime_set() and constructing timespec64 when needed?
> > 
> > 								Honza
> 
> The main advantage is that by using that, I didn't need to do quite so
> much of this conversion by hand. My coccinelle skills are pretty
> primitive. I went with whatever conversion was going to give minimal
> changes, to the existing accesses for the most part.
> 
> We could certainly do it the way you suggest, it just means having to
> re-touch a lot of this code by hand, or someone with better coccinelle
> chops suggesting a way to declare a temporary variables in place.

Well, maybe temporary variables aren't that convenient but we could provide
function setting ctime from sec & nsec value without having to declare
temporary timespec64? Attached is a semantic patch that should deal with
that - at least it seems to handle all the cases I've found.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

View attachment "ctime.cocci" of type "text/plain" (451 bytes)