[PATCH 040/119] xfs: create helpers for mapping, unmapping, and converting file fork extents

[Darrick J. Wong]

On Wed, Jul 13, 2016 at 02:28:25PM -0400, Brian Foster wrote:
> On Thu, Jun 16, 2016 at 06:22:08PM -0700, Darrick J. Wong wrote:
> > Create two helper functions to assist with mapping, unmapping, and
> > converting flag status of extents in a file's data/attr forks.  For
> > non-shared files we can use the _alloc, _free, and _convert functions;
> > when reflink comes these functions will be augmented to deal with
> > shared extents.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
> > ---
> >  fs/xfs/libxfs/xfs_rmap.c |   42 ++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 42 insertions(+)
> > 
> > 
> > diff --git a/fs/xfs/libxfs/xfs_rmap.c b/fs/xfs/libxfs/xfs_rmap.c
> > index f92eaa1..76fc5c2 100644
> > --- a/fs/xfs/libxfs/xfs_rmap.c
> > +++ b/fs/xfs/libxfs/xfs_rmap.c
> > @@ -1123,11 +1123,53 @@ done:
> >  	return error;
> >  }
> >  
> > +/*
> > + * Convert an unwritten extent to a real extent or vice versa.
> > + */
> > +STATIC int
> > +xfs_rmap_convert(
> > +	struct xfs_btree_cur	*cur,
> > +	xfs_agblock_t		bno,
> > +	xfs_extlen_t		len,
> > +	bool			unwritten,
> > +	struct xfs_owner_info	*oinfo)
> > +{
> > +	return __xfs_rmap_convert(cur, bno, len, unwritten, oinfo);
> > +}
> > +
> 
> Hmm, these all look like 1-1 mappings and they're static as well. Is the
> additional interface for reflink? If so, I think it might be better to
> punt this down to where it is really used (reflink).

Originally they were, but since the only caller of these functions is
_rmap_finish_one, this whole patch can drop out.

Later on in reflink, map/unmap/convert for reflinked files get totally
separate "shared" variants, along with corresponding RUI type codes.

Speaking of which, the shared and non-shared alloc/free/convert
functions are at a high level the same.  Each function has 8-10 places
where they differ (mostly in which btree functions they call) and I
wondered -- should I refactor them into a single megafunction that
takes a bunch of function pointers?  It's a little unwieldly to have
so much to pass in, but on the other hand we wouldn't have to maintain
two versions of basically the same code.

--D

> 
> Brian
> 
> >  #undef	NEW
> >  #undef	LEFT
> >  #undef	RIGHT
> >  #undef	PREV
> >  
> > +/*
> > + * Find an extent in the rmap btree and unmap it.
> > + */
> > +STATIC int
> > +xfs_rmap_unmap(
> > +	struct xfs_btree_cur	*cur,
> > +	xfs_agblock_t		bno,
> > +	xfs_extlen_t		len,
> > +	bool			unwritten,
> > +	struct xfs_owner_info	*oinfo)
> > +{
> > +	return __xfs_rmap_free(cur, bno, len, unwritten, oinfo);
> > +}
> > +
> > +/*
> > + * Find an extent in the rmap btree and map it.
> > + */
> > +STATIC int
> > +xfs_rmap_map(
> > +	struct xfs_btree_cur	*cur,
> > +	xfs_agblock_t		bno,
> > +	xfs_extlen_t		len,
> > +	bool			unwritten,
> > +	struct xfs_owner_info	*oinfo)
> > +{
> > +	return __xfs_rmap_alloc(cur, bno, len, unwritten, oinfo);
> > +}
> > +
> >  struct xfs_rmapbt_query_range_info {
> >  	xfs_rmapbt_query_range_fn	fn;
> >  	void				*priv;
> > 
> > _______________________________________________
> > xfs mailing list
> > xfs at oss.sgi.com
> > http://oss.sgi.com/mailman/listinfo/xfs
> 
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