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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 */
18struct bio_vec {
19 struct page *bv_page;
20 unsigned int bv_len;
21 unsigned int bv_offset;
22};
23
24struct 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
35struct 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
87static inline bool bvec_iter_advance(const struct bio_vec *bv,
88 struct bvec_iter *iter, unsigned bytes)
89{
90 unsigned int idx = iter->bi_idx;
91
92 if (WARN_ONCE(bytes > iter->bi_size,
93 "Attempted to advance past end of bvec iter\n")) {
94 iter->bi_size = 0;
95 return false;
96 }
97
98 iter->bi_size -= bytes;
99 bytes += iter->bi_bvec_done;
100
101 while (bytes && bytes >= bv[idx].bv_len) {
102 bytes -= bv[idx].bv_len;
103 idx++;
104 }
105
106 iter->bi_idx = idx;
107 iter->bi_bvec_done = bytes;
108 return true;
109}
110
111#define for_each_bvec(bvl, bio_vec, iter, start) \
112 for (iter = (start); \
113 (iter).bi_size && \
114 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
115 bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
116
117/* for iterating one bio from start to end */
118#define BVEC_ITER_ALL_INIT (struct bvec_iter) \
119{ \
120 .bi_sector = 0, \
121 .bi_size = UINT_MAX, \
122 .bi_idx = 0, \
123 .bi_bvec_done = 0, \
124}
125
126static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
127{
128 iter_all->done = 0;
129 iter_all->idx = 0;
130
131 return &iter_all->bv;
132}
133
134static inline void bvec_advance(const struct bio_vec *bvec,
135 struct bvec_iter_all *iter_all)
136{
137 struct bio_vec *bv = &iter_all->bv;
138
139 if (iter_all->done) {
140 bv->bv_page++;
141 bv->bv_offset = 0;
142 } else {
143 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
144 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
145 }
146 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
147 bvec->bv_len - iter_all->done);
148 iter_all->done += bv->bv_len;
149
150 if (iter_all->done == bvec->bv_len) {
151 iter_all->idx++;
152 iter_all->done = 0;
153 }
154}
155
156#endif /* __LINUX_BVEC_ITER_H */