xfs: support overlapping intervals in the rmap btree

Now that the generic btree code supports overlapping intervals, plug
in the rmap btree to this functionality.  We will need it to find
potential left neighbors in xfs_rmap_{alloc,free} later in the patch
set.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_rmap_btree.c

@@ -180,6 +180,35 @@ xfs_rmapbt_init_key_from_rec(
 	key->rmap.rm_offset = rec->rmap.rm_offset;
 }
 
+/*
+ * The high key for a reverse mapping record can be computed by shifting
+ * the startblock and offset to the highest value that would still map
+ * to that record.  In practice this means that we add blockcount-1 to
+ * the startblock for all records, and if the record is for a data/attr
+ * fork mapping, we add blockcount-1 to the offset too.
+ */
+STATIC void
+xfs_rmapbt_init_high_key_from_rec(
+	union xfs_btree_key	*key,
+	union xfs_btree_rec	*rec)
+{
+	__uint64_t		off;
+	int			adj;
+
+	adj = be32_to_cpu(rec->rmap.rm_blockcount) - 1;
+
+	key->rmap.rm_startblock = rec->rmap.rm_startblock;
+	be32_add_cpu(&key->rmap.rm_startblock, adj);
+	key->rmap.rm_owner = rec->rmap.rm_owner;
+	key->rmap.rm_offset = rec->rmap.rm_offset;
+	if (XFS_RMAP_NON_INODE_OWNER(be64_to_cpu(rec->rmap.rm_owner)) ||
+	    XFS_RMAP_IS_BMBT_BLOCK(be64_to_cpu(rec->rmap.rm_offset)))
+		return;
+	off = be64_to_cpu(key->rmap.rm_offset);
+	off = (XFS_RMAP_OFF(off) + adj) | (off & ~XFS_RMAP_OFF_MASK);
+	key->rmap.rm_offset = cpu_to_be64(off);
+}
+
 STATIC void
 xfs_rmapbt_init_rec_from_cur(
 	struct xfs_btree_cur	*cur,
@@ -235,6 +264,38 @@ xfs_rmapbt_key_diff(
 	return 0;
 }
 
+STATIC __int64_t
+xfs_rmapbt_diff_two_keys(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*k1,
+	union xfs_btree_key	*k2)
+{
+	struct xfs_rmap_key	*kp1 = &k1->rmap;
+	struct xfs_rmap_key	*kp2 = &k2->rmap;
+	__int64_t		d;
+	__u64			x, y;
+
+	d = (__int64_t)be32_to_cpu(kp1->rm_startblock) -
+		       be32_to_cpu(kp2->rm_startblock);
+	if (d)
+		return d;
+
+	x = be64_to_cpu(kp1->rm_owner);
+	y = be64_to_cpu(kp2->rm_owner);
+	if (x > y)
+		return 1;
+	else if (y > x)
+		return -1;
+
+	x = XFS_RMAP_OFF(be64_to_cpu(kp1->rm_offset));
+	y = XFS_RMAP_OFF(be64_to_cpu(kp2->rm_offset));
+	if (x > y)
+		return 1;
+	else if (y > x)
+		return -1;
+	return 0;
+}
+
 static bool
 xfs_rmapbt_verify(
 	struct xfs_buf		*bp)
@@ -382,10 +443,12 @@ static const struct xfs_btree_ops xfs_rmapbt_ops = {
 	.get_minrecs		= xfs_rmapbt_get_minrecs,
 	.get_maxrecs		= xfs_rmapbt_get_maxrecs,
 	.init_key_from_rec	= xfs_rmapbt_init_key_from_rec,
+	.init_high_key_from_rec	= xfs_rmapbt_init_high_key_from_rec,
 	.init_rec_from_cur	= xfs_rmapbt_init_rec_from_cur,
 	.init_ptr_from_cur	= xfs_rmapbt_init_ptr_from_cur,
 	.key_diff		= xfs_rmapbt_key_diff,
 	.buf_ops		= &xfs_rmapbt_buf_ops,
+	.diff_two_keys		= xfs_rmapbt_diff_two_keys,
 #if defined(DEBUG) || defined(XFS_WARN)
 	.keys_inorder		= xfs_rmapbt_keys_inorder,
 	.recs_inorder		= xfs_rmapbt_recs_inorder,
@@ -412,8 +475,9 @@ xfs_rmapbt_init_cursor(
 	cur = kmem_zone_zalloc(xfs_btree_cur_zone, KM_NOFS);
 	cur->bc_tp = tp;
 	cur->bc_mp = mp;
+	/* Overlapping btree; 2 keys per pointer. */
 	cur->bc_btnum = XFS_BTNUM_RMAP;
-	cur->bc_flags = XFS_BTREE_CRC_BLOCKS;
+	cur->bc_flags = XFS_BTREE_CRC_BLOCKS | XFS_BTREE_OVERLAPPING;
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
 	cur->bc_ops = &xfs_rmapbt_ops;
 	cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]);
@@ -438,7 +502,7 @@ xfs_rmapbt_maxrecs(
 	if (leaf)
 		return blocklen / sizeof(struct xfs_rmap_rec);
 	return blocklen /
-		(sizeof(struct xfs_rmap_key) + sizeof(xfs_rmap_ptr_t));
+		(2 * sizeof(struct xfs_rmap_key) + sizeof(xfs_rmap_ptr_t));
 }
 
 /* Compute the maximum height of an rmap btree. */

fs/xfs/libxfs/xfs_rmap_btree.h

@@ -38,12 +38,18 @@ struct xfs_mount;
 #define XFS_RMAP_KEY_ADDR(block, index) \
 	((struct xfs_rmap_key *) \
 		((char *)(block) + XFS_RMAP_BLOCK_LEN + \
-		 ((index) - 1) * sizeof(struct xfs_rmap_key)))
+		 ((index) - 1) * 2 * sizeof(struct xfs_rmap_key)))
+
+#define XFS_RMAP_HIGH_KEY_ADDR(block, index) \
+	((struct xfs_rmap_key *) \
+		((char *)(block) + XFS_RMAP_BLOCK_LEN + \
+		 sizeof(struct xfs_rmap_key) + \
+		 ((index) - 1) * 2 * sizeof(struct xfs_rmap_key)))
 
 #define XFS_RMAP_PTR_ADDR(block, index, maxrecs) \
 	((xfs_rmap_ptr_t *) \
 		((char *)(block) + XFS_RMAP_BLOCK_LEN + \
-		 (maxrecs) * sizeof(struct xfs_rmap_key) + \
+		 (maxrecs) * 2 * sizeof(struct xfs_rmap_key) + \
 		 ((index) - 1) * sizeof(xfs_rmap_ptr_t)))
 
 struct xfs_btree_cur *xfs_rmapbt_init_cursor(struct xfs_mount *mp,