xfs: introduce realtime rmap btree ondisk definitions

Add the ondisk structure definitions for realtime rmap btrees. The
realtime rmap btree will be rooted from a hidden inode so it needs to
have a separate btree block magic and pointer format.

Next, add everything needed to read, write and manipulate rmap btree
blocks. This prepares the way for connecting the btree operations
implementation, though embedding the rtrmap btree root in the inode
comes later in the series.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 4d47a3e723aa..469fc7afa591 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -1726,6 +1726,16 @@ typedef __be32 xfs_rmap_ptr_t;
 	 XFS_IBT_BLOCK(mp) + 1)
 
 /*
+ * Realtime Reverse mapping btree format definitions
+ *
+ * This is a btree for reverse mapping records for realtime volumes
+ */
+#define	XFS_RTRMAP_CRC_MAGIC	0x4d415052	/* 'MAPR' */
+
+/* inode-based btree pointer type */
+typedef __be64 xfs_rtrmap_ptr_t;
+
+/*
  * Reference Count Btree format definitions
  *
  */