1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * Copyright (C) 2021-2023 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <djwong@kernel.org>
5 */
6 #ifndef __XFS_SCRUB_XFARRAY_H__
7 #define __XFS_SCRUB_XFARRAY_H__
8
9 /* xfile array index type, along with cursor initialization */
10 typedef uint64_t xfarray_idx_t;
11 #define XFARRAY_CURSOR_INIT ((__force xfarray_idx_t)0)
12
13 /* Iterate each index of an xfile array. */
14 #define foreach_xfarray_idx(array, idx) \
15 for ((idx) = XFARRAY_CURSOR_INIT; \
16 (idx) < xfarray_length(array); \
17 (idx)++)
18
19 struct xfarray {
20 /* Underlying file that backs the array. */
21 struct xfile *xfile;
22
23 /* Number of array elements. */
24 xfarray_idx_t nr;
25
26 /* Maximum possible array size. */
27 xfarray_idx_t max_nr;
28
29 /* Number of unset slots in the array below @nr. */
30 uint64_t unset_slots;
31
32 /* Size of an array element. */
33 size_t obj_size;
34
35 /* log2 of array element size, if possible. */
36 int obj_size_log;
37 };
38
39 int xfarray_create(const char *descr, unsigned long long required_capacity,
40 size_t obj_size, struct xfarray **arrayp);
41 void xfarray_destroy(struct xfarray *array);
42 int xfarray_load(struct xfarray *array, xfarray_idx_t idx, void *ptr);
43 int xfarray_unset(struct xfarray *array, xfarray_idx_t idx);
44 int xfarray_store(struct xfarray *array, xfarray_idx_t idx, const void *ptr);
45 int xfarray_store_anywhere(struct xfarray *array, const void *ptr);
46 bool xfarray_element_is_null(struct xfarray *array, const void *ptr);
47
48 /* Append an element to the array. */
xfarray_append(struct xfarray * array,const void * ptr)49 static inline int xfarray_append(struct xfarray *array, const void *ptr)
50 {
51 return xfarray_store(array, array->nr, ptr);
52 }
53
54 uint64_t xfarray_length(struct xfarray *array);
55 int xfarray_load_next(struct xfarray *array, xfarray_idx_t *idx, void *rec);
56
57 /* Declarations for xfile array sort functionality. */
58
59 typedef cmp_func_t xfarray_cmp_fn;
60
61 /* Perform an in-memory heapsort for small subsets. */
62 #define XFARRAY_ISORT_SHIFT (4)
63 #define XFARRAY_ISORT_NR (1U << XFARRAY_ISORT_SHIFT)
64
65 /* Evalulate this many points to find the qsort pivot. */
66 #define XFARRAY_QSORT_PIVOT_NR (9)
67
68 struct xfarray_sortinfo {
69 struct xfarray *array;
70
71 /* Comparison function for the sort. */
72 xfarray_cmp_fn cmp_fn;
73
74 /* Maximum height of the partition stack. */
75 uint8_t max_stack_depth;
76
77 /* Current height of the partition stack. */
78 int8_t stack_depth;
79
80 /* Maximum stack depth ever used. */
81 uint8_t max_stack_used;
82
83 /* XFARRAY_SORT_* flags; see below. */
84 unsigned int flags;
85
86 /* Cache a page here for faster access. */
87 struct xfile_page xfpage;
88 void *page_kaddr;
89
90 #ifdef DEBUG
91 /* Performance statistics. */
92 uint64_t loads;
93 uint64_t stores;
94 uint64_t compares;
95 uint64_t heapsorts;
96 #endif
97 /*
98 * Extra bytes are allocated beyond the end of the structure to store
99 * quicksort information. C does not permit multiple VLAs per struct,
100 * so we document all of this in a comment.
101 *
102 * Pretend that we have a typedef for array records:
103 *
104 * typedef char[array->obj_size] xfarray_rec_t;
105 *
106 * First comes the quicksort partition stack:
107 *
108 * xfarray_idx_t lo[max_stack_depth];
109 * xfarray_idx_t hi[max_stack_depth];
110 *
111 * union {
112 *
113 * If for a given subset we decide to use an in-memory sort, we use a
114 * block of scratchpad records here to compare items:
115 *
116 * xfarray_rec_t scratch[ISORT_NR];
117 *
118 * Otherwise, we want to partition the records to partition the array.
119 * We store the chosen pivot record at the start of the scratchpad area
120 * and use the rest to sample some records to estimate the median.
121 * The format of the qsort_pivot array enables us to use the kernel
122 * heapsort function to place the median value in the middle.
123 *
124 * struct {
125 * xfarray_rec_t pivot;
126 * struct {
127 * xfarray_rec_t rec; (rounded up to 8 bytes)
128 * xfarray_idx_t idx;
129 * } qsort_pivot[QSORT_PIVOT_NR];
130 * };
131 * }
132 */
133 };
134
135 /* Sort can be interrupted by a fatal signal. */
136 #define XFARRAY_SORT_KILLABLE (1U << 0)
137
138 int xfarray_sort(struct xfarray *array, xfarray_cmp_fn cmp_fn,
139 unsigned int flags);
140
141 #endif /* __XFS_SCRUB_XFARRAY_H__ */
142