1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * bvec iterator
4 *
5 * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
6 */
7 #ifndef __LINUX_BVEC_ITER_H
8 #define __LINUX_BVEC_ITER_H
9
10 #include <linux/kernel.h>
11 #include <linux/bug.h>
12 #include <linux/errno.h>
13 #include <linux/mm.h>
14
15 /*
16 * was unsigned short, but we might as well be ready for > 64kB I/O pages
17 */
18 struct bio_vec {
19 struct page *bv_page;
20 unsigned int bv_len;
21 unsigned int bv_offset;
22 };
23
24 struct bvec_iter {
25 sector_t bi_sector; /* device address in 512 byte
26 sectors */
27 unsigned int bi_size; /* residual I/O count */
28
29 unsigned int bi_idx; /* current index into bvl_vec */
30
31 unsigned int bi_bvec_done; /* number of bytes completed in
32 current bvec */
33 };
34
35 struct bvec_iter_all {
36 struct bio_vec bv;
37 int idx;
38 unsigned done;
39 };
40
41 /*
42 * various member access, note that bio_data should of course not be used
43 * on highmem page vectors
44 */
45 #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx])
46
47 /* multi-page (mp_bvec) helpers */
48 #define mp_bvec_iter_page(bvec, iter) \
49 (__bvec_iter_bvec((bvec), (iter))->bv_page)
50
51 #define mp_bvec_iter_len(bvec, iter) \
52 min((iter).bi_size, \
53 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
54
55 #define mp_bvec_iter_offset(bvec, iter) \
56 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
57
58 #define mp_bvec_iter_page_idx(bvec, iter) \
59 (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
60
61 #define mp_bvec_iter_bvec(bvec, iter) \
62 ((struct bio_vec) { \
63 .bv_page = mp_bvec_iter_page((bvec), (iter)), \
64 .bv_len = mp_bvec_iter_len((bvec), (iter)), \
65 .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \
66 })
67
68 /* For building single-page bvec in flight */
69 #define bvec_iter_offset(bvec, iter) \
70 (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
71
72 #define bvec_iter_len(bvec, iter) \
73 min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \
74 PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
75
76 #define bvec_iter_page(bvec, iter) \
77 (mp_bvec_iter_page((bvec), (iter)) + \
78 mp_bvec_iter_page_idx((bvec), (iter)))
79
80 #define bvec_iter_bvec(bvec, iter) \
81 ((struct bio_vec) { \
82 .bv_page = bvec_iter_page((bvec), (iter)), \
83 .bv_len = bvec_iter_len((bvec), (iter)), \
84 .bv_offset = bvec_iter_offset((bvec), (iter)), \
85 })
86
bvec_iter_advance(const struct bio_vec * bv,struct bvec_iter * iter,unsigned bytes)87 static inline bool bvec_iter_advance(const struct bio_vec *bv,
88 struct bvec_iter *iter, unsigned bytes)
89 {
90 if (WARN_ONCE(bytes > iter->bi_size,
91 "Attempted to advance past end of bvec iter\n")) {
92 iter->bi_size = 0;
93 return false;
94 }
95
96 while (bytes) {
97 const struct bio_vec *cur = bv + iter->bi_idx;
98 unsigned len = min3(bytes, iter->bi_size,
99 cur->bv_len - iter->bi_bvec_done);
100
101 bytes -= len;
102 iter->bi_size -= len;
103 iter->bi_bvec_done += len;
104
105 if (iter->bi_bvec_done == cur->bv_len) {
106 iter->bi_bvec_done = 0;
107 iter->bi_idx++;
108 }
109 }
110 return true;
111 }
112
113 #define for_each_bvec(bvl, bio_vec, iter, start) \
114 for (iter = (start); \
115 (iter).bi_size && \
116 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
117 bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
118
119 /* for iterating one bio from start to end */
120 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \
121 { \
122 .bi_sector = 0, \
123 .bi_size = UINT_MAX, \
124 .bi_idx = 0, \
125 .bi_bvec_done = 0, \
126 }
127
bvec_init_iter_all(struct bvec_iter_all * iter_all)128 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
129 {
130 iter_all->done = 0;
131 iter_all->idx = 0;
132
133 return &iter_all->bv;
134 }
135
bvec_advance(const struct bio_vec * bvec,struct bvec_iter_all * iter_all)136 static inline void bvec_advance(const struct bio_vec *bvec,
137 struct bvec_iter_all *iter_all)
138 {
139 struct bio_vec *bv = &iter_all->bv;
140
141 if (iter_all->done) {
142 bv->bv_page++;
143 bv->bv_offset = 0;
144 } else {
145 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
146 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
147 }
148 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
149 bvec->bv_len - iter_all->done);
150 iter_all->done += bv->bv_len;
151
152 if (iter_all->done == bvec->bv_len) {
153 iter_all->idx++;
154 iter_all->done = 0;
155 }
156 }
157
158 /*
159 * Get the last single-page segment from the multi-page bvec and store it
160 * in @seg
161 */
mp_bvec_last_segment(const struct bio_vec * bvec,struct bio_vec * seg)162 static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
163 struct bio_vec *seg)
164 {
165 unsigned total = bvec->bv_offset + bvec->bv_len;
166 unsigned last_page = (total - 1) / PAGE_SIZE;
167
168 seg->bv_page = bvec->bv_page + last_page;
169
170 /* the whole segment is inside the last page */
171 if (bvec->bv_offset >= last_page * PAGE_SIZE) {
172 seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
173 seg->bv_len = bvec->bv_len;
174 } else {
175 seg->bv_offset = 0;
176 seg->bv_len = total - last_page * PAGE_SIZE;
177 }
178 }
179
180 #endif /* __LINUX_BVEC_ITER_H */
181
