1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Copyright (C) 2018-2023 Oracle.  All Rights Reserved.
  4 * Author: Darrick J. Wong <djwong@kernel.org>
  5 */
  6#include "xfs.h"
  7#include "xfs_shared.h"
  8#include "xfs_bit.h"
  9#include "xfs_format.h"
 10#include "xfs_trans_resv.h"
 11#include "xfs_mount.h"
 12#include "xfs_btree.h"
 13#include "bitmap.h"
 14#include "scrub/agb_bitmap.h"
 15
 16/*
 17 * Record all btree blocks seen while iterating all records of a btree.
 18 *
 19 * We know that the btree query_all function starts at the left edge and walks
 20 * towards the right edge of the tree.  Therefore, we know that we can walk up
 21 * the btree cursor towards the root; if the pointer for a given level points
 22 * to the first record/key in that block, we haven't seen this block before;
 23 * and therefore we need to remember that we saw this block in the btree.
 24 *
 25 * So if our btree is:
 26 *
 27 *    4
 28 *  / | \
 29 * 1  2  3
 30 *
 31 * Pretend for this example that each leaf block has 100 btree records.  For
 32 * the first btree record, we'll observe that bc_levels[0].ptr == 1, so we
 33 * record that we saw block 1.  Then we observe that bc_levels[1].ptr == 1, so
 34 * we record block 4.  The list is [1, 4].
 35 *
 36 * For the second btree record, we see that bc_levels[0].ptr == 2, so we exit
 37 * the loop.  The list remains [1, 4].
 38 *
 39 * For the 101st btree record, we've moved onto leaf block 2.  Now
 40 * bc_levels[0].ptr == 1 again, so we record that we saw block 2.  We see that
 41 * bc_levels[1].ptr == 2, so we exit the loop.  The list is now [1, 4, 2].
 42 *
 43 * For the 102nd record, bc_levels[0].ptr == 2, so we continue.
 44 *
 45 * For the 201st record, we've moved on to leaf block 3.
 46 * bc_levels[0].ptr == 1, so we add 3 to the list.  Now it is [1, 4, 2, 3].
 47 *
 48 * For the 300th record we just exit, with the list being [1, 4, 2, 3].
 49 */
 50
 51/* Mark a btree block to the agblock bitmap. */
 52STATIC int
 53xagb_bitmap_visit_btblock(
 54	struct xfs_btree_cur	*cur,
 55	int			level,
 56	void			*priv)
 57{
 58	struct xagb_bitmap	*bitmap = priv;
 59	struct xfs_buf		*bp;
 60	xfs_fsblock_t		fsbno;
 61	xfs_agblock_t		agbno;
 62
 63	xfs_btree_get_block(cur, level, &bp);
 64	if (!bp)
 65		return 0;
 66
 67	fsbno = XFS_DADDR_TO_FSB(cur->bc_mp, xfs_buf_daddr(bp));
 68	agbno = XFS_FSB_TO_AGBNO(cur->bc_mp, fsbno);
 69
 70	return xagb_bitmap_set(bitmap, agbno, 1);
 71}
 72
 73/* Mark all (per-AG) btree blocks in the agblock bitmap. */
 74int
 75xagb_bitmap_set_btblocks(
 76	struct xagb_bitmap	*bitmap,
 77	struct xfs_btree_cur	*cur)
 78{
 79	return xfs_btree_visit_blocks(cur, xagb_bitmap_visit_btblock,
 80			XFS_BTREE_VISIT_ALL, bitmap);
 81}
 82
 83/*
 84 * Record all the buffers pointed to by the btree cursor.  Callers already
 85 * engaged in a btree walk should call this function to capture the list of
 86 * blocks going from the leaf towards the root.
 87 */
 88int
 89xagb_bitmap_set_btcur_path(
 90	struct xagb_bitmap	*bitmap,
 91	struct xfs_btree_cur	*cur)
 92{
 93	int			i;
 94	int			error;
 95
 96	for (i = 0; i < cur->bc_nlevels && cur->bc_levels[i].ptr == 1; i++) {
 97		error = xagb_bitmap_visit_btblock(cur, i, bitmap);
 98		if (error)
 99			return error;
100	}
101
102	return 0;
103}