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

Darrick J. Wong
2016-07-13T18:47:58Z

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@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@oss.sgi.com
> > http://oss.sgi.com/mailman/listinfo/xfs
>
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