[XFS] add helpers for addressing entities inside a btree block

Add new helpers in xfs_btree.c to find the record, key and block pointer
entries inside a btree block. To implement this genericly the
->get_maxrecs methods and two new xfs_btree_ops entries for the key and
record sizes are used. Also add a big comment describing how the
addressing inside a btree block works.

Note that these helpers are unused until users are introduced in the next
patches and this patch will thus cause some harmless compiler warnings.

SGI-PV: 985583

SGI-Modid: xfs-linux-melb:xfs-kern:32189a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Signed-off-by: Bill O'Donnell <billodo@sgi.com>
Signed-off-by: David Chinner <david@fromorbit.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/xfs/xfs_alloc_btree.c b/fs/xfs/xfs_alloc_btree.c
index 1f268b6f4362..9e2421c31a36 100644
--- a/fs/xfs/xfs_alloc_btree.c
+++ b/fs/xfs/xfs_alloc_btree.c
@@ -2294,6 +2294,9 @@ xfs_allocbt_trace_record(
 #endif /* XFS_BTREE_TRACE */
 
 static const struct xfs_btree_ops xfs_allocbt_ops = {
+        .rec_len                = sizeof(xfs_alloc_rec_t),
+        .key_len                = sizeof(xfs_alloc_key_t),
+
         .dup_cursor             = xfs_allocbt_dup_cursor,
         .get_maxrecs            = xfs_allocbt_get_maxrecs,