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_NULLIDX ((__force xfarray_idx_t)-1ULL)
12 #define XFARRAY_CURSOR_INIT ((__force xfarray_idx_t)0)
13
14 /* Iterate each index of an xfile array. */
15 #define foreach_xfarray_idx(array, idx) \
16 for ((idx) = XFARRAY_CURSOR_INIT; \
17 (idx) < xfarray_length(array); \
18 (idx)++)
19
20 struct xfarray {
21 /* Underlying file that backs the array. */
22 struct xfile *xfile;
23
24 /* Number of array elements. */
25 xfarray_idx_t nr;
26
27 /* Maximum possible array size. */
28 xfarray_idx_t max_nr;
29
30 /* Number of unset slots in the array below @nr. */
31 uint64_t unset_slots;
32
33 /* Size of an array element. */
34 size_t obj_size;
35
36 /* log2 of array element size, if possible. */
37 int obj_size_log;
38 };
39
40 int xfarray_create(const char *descr, unsigned long long required_capacity,
41 size_t obj_size, struct xfarray **arrayp);
42 void xfarray_destroy(struct xfarray *array);
43 int xfarray_load(struct xfarray *array, xfarray_idx_t idx, void *ptr);
44 int xfarray_unset(struct xfarray *array, xfarray_idx_t idx);
45 int xfarray_store(struct xfarray *array, xfarray_idx_t idx, const void *ptr);
46 int xfarray_store_anywhere(struct xfarray *array, const void *ptr);
47 bool xfarray_element_is_null(struct xfarray *array, const void *ptr);
48 void xfarray_truncate(struct xfarray *array);
49 unsigned long long xfarray_bytes(struct xfarray *array);
50
51 /*
52 * Load an array element, but zero the buffer if there's no data because we
53 * haven't stored to that array element yet.
54 */
55 static inline int
56 xfarray_load_sparse(
57 struct xfarray *array,
58 uint64_t idx,
59 void *rec)
60 {
61 int error = xfarray_load(array, idx, rec);
62
63 if (error == -ENODATA) {
64 memset(rec, 0, array->obj_size);
65 return 0;
66 }
67 return error;
68 }
69
70 /* Append an element to the array. */
71 static inline int xfarray_append(struct xfarray *array, const void *ptr)
72 {
73 return xfarray_store(array, array->nr, ptr);
74 }
75
76 uint64_t xfarray_length(struct xfarray *array);
77 int xfarray_load_next(struct xfarray *array, xfarray_idx_t *idx, void *rec);
78
79 /*
80 * Iterate the non-null elements in a sparse xfarray. Callers should
81 * initialize *idx to XFARRAY_CURSOR_INIT before the first call; on return, it
82 * will be set to one more than the index of the record that was retrieved.
83 * Returns 1 if a record was retrieved, 0 if there weren't any more records, or
84 * a negative errno.
85 */
86 static inline int
87 xfarray_iter(
88 struct xfarray *array,
89 xfarray_idx_t *idx,
90 void *rec)
91 {
92 int ret = xfarray_load_next(array, idx, rec);
93
94 if (ret == -ENODATA)
95 return 0;
96 if (ret == 0)
97 return 1;
98 return ret;
99 }
100
101 /* Declarations for xfile array sort functionality. */
102
103 typedef cmp_func_t xfarray_cmp_fn;
104
105 /* Perform an in-memory heapsort for small subsets. */
106 #define XFARRAY_ISORT_SHIFT (4)
107 #define XFARRAY_ISORT_NR (1U << XFARRAY_ISORT_SHIFT)
108
109 /* Evalulate this many points to find the qsort pivot. */
110 #define XFARRAY_QSORT_PIVOT_NR (9)
111
112 struct xfarray_sortinfo {
113 struct xfarray *array;
114
115 /* Comparison function for the sort. */
116 xfarray_cmp_fn cmp_fn;
117
118 /* Maximum height of the partition stack. */
119 uint8_t max_stack_depth;
120
121 /* Current height of the partition stack. */
122 int8_t stack_depth;
123
124 /* Maximum stack depth ever used. */
125 uint8_t max_stack_used;
126
127 /* XFARRAY_SORT_* flags; see below. */
128 unsigned int flags;
129
130 /* next time we want to cond_resched() */
131 struct xchk_relax relax;
132
133 /* Cache a folio here for faster scanning for pivots */
134 struct folio *folio;
135
136 /* First array index in folio that is completely readable */
137 xfarray_idx_t first_folio_idx;
138
139 /* Last array index in folio that is completely readable */
140 xfarray_idx_t last_folio_idx;
141
142 #ifdef DEBUG
143 /* Performance statistics. */
144 uint64_t loads;
145 uint64_t stores;
146 uint64_t compares;
147 uint64_t heapsorts;
148 #endif
149 /*
150 * Extra bytes are allocated beyond the end of the structure to store
151 * quicksort information. C does not permit multiple VLAs per struct,
152 * so we document all of this in a comment.
153 *
154 * Pretend that we have a typedef for array records:
155 *
156 * typedef char[array->obj_size] xfarray_rec_t;
157 *
158 * First comes the quicksort partition stack:
159 *
160 * xfarray_idx_t lo[max_stack_depth];
161 * xfarray_idx_t hi[max_stack_depth];
162 *
163 * union {
164 *
165 * If for a given subset we decide to use an in-memory sort, we use a
166 * block of scratchpad records here to compare items:
167 *
168 * xfarray_rec_t scratch[ISORT_NR];
169 *
170 * Otherwise, we want to partition the records to partition the array.
171 * We store the chosen pivot record at the start of the scratchpad area
172 * and use the rest to sample some records to estimate the median.
173 * The format of the qsort_pivot array enables us to use the kernel
174 * heapsort function to place the median value in the middle.
175 *
176 * struct {
177 * xfarray_rec_t pivot;
178 * struct {
179 * xfarray_rec_t rec; (rounded up to 8 bytes)
180 * xfarray_idx_t idx;
181 * } qsort_pivot[QSORT_PIVOT_NR];
182 * };
183 * }
184 */
185 };
186
187 /* Sort can be interrupted by a fatal signal. */
188 #define XFARRAY_SORT_KILLABLE (1U << 0)
189
190 int xfarray_sort(struct xfarray *array, xfarray_cmp_fn cmp_fn,
191 unsigned int flags);
192
193 #endif /* __XFS_SCRUB_XFARRAY_H__ */
194
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