xfs: convert xbitmap to interval tree

Convert the xbitmap code to use interval trees instead of linked lists.
This reduces the amount of coding required to handle the disunion
operation and in the future will make it easier to set bits in arbitrary
order yet later be able to extract maximally sized extents, which we'll
need for rebuilding certain structures.  We define our own interval tree
type so that it can deal with 64-bit indices even on 32-bit machines.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/scrub/agheader_repair.c

@@ -663,7 +663,7 @@ xrep_agfl_fill(
 }
 
 /* Write out a totally new AGFL. */
-STATIC void
+STATIC int
 xrep_agfl_init_header(
 	struct xfs_scrub	*sc,
 	struct xfs_buf		*agfl_bp,
@@ -676,6 +676,7 @@ xrep_agfl_init_header(
 	};
 	struct xfs_mount	*mp = sc->mp;
 	struct xfs_agfl		*agfl;
+	int			error;
 
 	ASSERT(flcount <= xfs_agfl_size(mp));
 
@@ -697,12 +698,15 @@ xrep_agfl_init_header(
 	xbitmap_init(&af.used_extents);
 	af.agfl_bno = xfs_buf_to_agfl_bno(agfl_bp),
 	xbitmap_walk(agfl_extents, xrep_agfl_fill, &af);
-	xbitmap_disunion(agfl_extents, &af.used_extents);
+	error = xbitmap_disunion(agfl_extents, &af.used_extents);
+	if (error)
+		return error;
 
 	/* Write new AGFL to disk. */
 	xfs_trans_buf_set_type(sc->tp, agfl_bp, XFS_BLFT_AGFL_BUF);
 	xfs_trans_log_buf(sc->tp, agfl_bp, 0, BBTOB(agfl_bp->b_length) - 1);
 	xbitmap_destroy(&af.used_extents);
+	return 0;
 }
 
 /* Repair the AGFL. */
@@ -755,7 +759,9 @@ xrep_agfl(
 	 * buffers until we know that part works.
 	 */
 	xrep_agfl_update_agf(sc, agf_bp, flcount);
-	xrep_agfl_init_header(sc, agfl_bp, &agfl_extents, flcount);
+	error = xrep_agfl_init_header(sc, agfl_bp, &agfl_extents, flcount);
+	if (error)
+		goto err;
 
 	/*
 	 * Ok, the AGFL should be ready to go now.  Roll the transaction to

fs/xfs/scrub/bitmap.h

@@ -6,19 +6,14 @@
 #ifndef __XFS_SCRUB_BITMAP_H__
 #define __XFS_SCRUB_BITMAP_H__
 
-struct xbitmap_range {
-	struct list_head	list;
-	uint64_t		start;
-	uint64_t		len;
-};
-
 struct xbitmap {
-	struct list_head	list;
+	struct rb_root_cached	xb_root;
 };
 
 void xbitmap_init(struct xbitmap *bitmap);
 void xbitmap_destroy(struct xbitmap *bitmap);
 
+int xbitmap_clear(struct xbitmap *bitmap, uint64_t start, uint64_t len);
 int xbitmap_set(struct xbitmap *bitmap, uint64_t start, uint64_t len);
 int xbitmap_disunion(struct xbitmap *bitmap, struct xbitmap *sub);
 int xbitmap_set_btcur_path(struct xbitmap *bitmap,
@@ -42,4 +37,6 @@ typedef int (*xbitmap_walk_bits_fn)(uint64_t bit, void *priv);
 int xbitmap_walk_bits(struct xbitmap *bitmap, xbitmap_walk_bits_fn fn,
 		void *priv);
 
+bool xbitmap_empty(struct xbitmap *bitmap);
+
 #endif	/* __XFS_SCRUB_BITMAP_H__ */