xfs: add scrub cross-referencing helpers for the rmap btrees

Add a couple of functions to the rmap btrees that will be used
to cross-reference metadata against the rmapbt.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_rmap.c

@@ -2387,3 +2387,70 @@ xfs_rmap_compare(
 	else
 		return 0;
 }
+
+/* Is there a record covering a given extent? */
+int
+xfs_rmap_has_record(
+	struct xfs_btree_cur	*cur,
+	xfs_agblock_t		bno,
+	xfs_extlen_t		len,
+	bool			*exists)
+{
+	union xfs_btree_irec	low;
+	union xfs_btree_irec	high;
+
+	memset(&low, 0, sizeof(low));
+	low.r.rm_startblock = bno;
+	memset(&high, 0xFF, sizeof(high));
+	high.r.rm_startblock = bno + len - 1;
+
+	return xfs_btree_has_record(cur, &low, &high, exists);
+}
+
+/*
+ * Is there a record for this owner completely covering a given physical
+ * extent?  If so, *has_rmap will be set to true.  If there is no record
+ * or the record only covers part of the range, we set *has_rmap to false.
+ * This function doesn't perform range lookups or offset checks, so it is
+ * not suitable for checking data fork blocks.
+ */
+int
+xfs_rmap_record_exists(
+	struct xfs_btree_cur	*cur,
+	xfs_agblock_t		bno,
+	xfs_extlen_t		len,
+	struct xfs_owner_info	*oinfo,
+	bool			*has_rmap)
+{
+	uint64_t		owner;
+	uint64_t		offset;
+	unsigned int		flags;
+	int			has_record;
+	struct xfs_rmap_irec	irec;
+	int			error;
+
+	xfs_owner_info_unpack(oinfo, &owner, &offset, &flags);
+	ASSERT(XFS_RMAP_NON_INODE_OWNER(owner) ||
+	       (flags & XFS_RMAP_BMBT_BLOCK));
+
+	error = xfs_rmap_lookup_le(cur, bno, len, owner, offset, flags,
+			&has_record);
+	if (error)
+		return error;
+	if (!has_record) {
+		*has_rmap = false;
+		return 0;
+	}
+
+	error = xfs_rmap_get_rec(cur, &irec, &has_record);
+	if (error)
+		return error;
+	if (!has_record) {
+		*has_rmap = false;
+		return 0;
+	}
+
+	*has_rmap = (irec.rm_owner == owner && irec.rm_startblock <= bno &&
+		     irec.rm_startblock + irec.rm_blockcount >= bno + len);
+	return 0;
+}

fs/xfs/libxfs/xfs_rmap.h

@@ -233,5 +233,10 @@ int xfs_rmap_compare(const struct xfs_rmap_irec *a,
 union xfs_btree_rec;
 int xfs_rmap_btrec_to_irec(union xfs_btree_rec *rec,
 		struct xfs_rmap_irec *irec);
+int xfs_rmap_has_record(struct xfs_btree_cur *cur, xfs_agblock_t bno,
+		xfs_extlen_t len, bool *exists);
+int xfs_rmap_record_exists(struct xfs_btree_cur *cur, xfs_agblock_t bno,
+		xfs_extlen_t len, struct xfs_owner_info *oinfo,
+		bool *has_rmap);
 
 #endif	/* __XFS_RMAP_H__ */