Re: [PATCH] fs, dax: unify IOMAP_F_DIRTY read vs write handling policy in the dax core

[Christoph Hellwig <hch@infradead.org>]

On Tue, Nov 14, 2017 at 03:12:28PM +1100, Dave Chinner wrote:
> On Mon, Nov 13, 2017 at 05:27:54PM -0800, Dan Williams wrote:
> > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> > index b43be199fbdf..888b60189983 100644
> > --- a/fs/xfs/xfs_iomap.c
> > +++ b/fs/xfs/xfs_iomap.c
> > @@ -1087,9 +1087,9 @@ xfs_file_iomap_begin(
> >  		trace_xfs_iomap_found(ip, offset, length, 0, &imap);
> >  	}
> >  
> > -	if ((flags & IOMAP_WRITE) && xfs_ipincount(ip) &&
> > -	    (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
> > -		iomap->flags |= IOMAP_F_DIRTY;
> > +	if (xfs_ipincount(ip))
> > +		if (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP)
> > +			iomap->flags |= IOMAP_F_DIRTY;
> 
> Please make a helper for this, and use it in xfs_file_fsync() where
> the same dirty checks are done. e.g.

Let's keep that sort of cleanup separate.  I initially considered
it when doing the MAP_SYNC work, but fsync works a little different
in that it looks at ili_last_lsn, so your little helper below won't
work as-is.  You can send it as an incremental patch later and we
can see if we can come up with something workable.