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. */
52 STATIC int
53 xagb_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. */
74 int
75 xagb_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 */
88 int
89 xagb_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 }
104
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