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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 * struct bio_vec - a contiguous range of physical memory addresses
17 * @bv_page: First page associated with the address range.
18 * @bv_len: Number of bytes in the address range.
19 * @bv_offset: Start of the address range relative to the start of @bv_page.
20 *
21 * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
22 *
23 * nth_page(@bv_page, n) == @bv_page + n
24 *
25 * This holds because page_is_mergeable() checks the above property.
26 */
27struct bio_vec {
28 struct page *bv_page;
29 unsigned int bv_len;
30 unsigned int bv_offset;
31};
32
33struct bvec_iter {
34 sector_t bi_sector; /* device address in 512 byte
35 sectors */
36 unsigned int bi_size; /* residual I/O count */
37
38 unsigned int bi_idx; /* current index into bvl_vec */
39
40 unsigned int bi_bvec_done; /* number of bytes completed in
41 current bvec */
42};
43
44struct bvec_iter_all {
45 struct bio_vec bv;
46 int idx;
47 unsigned done;
48};
49
50/*
51 * various member access, note that bio_data should of course not be used
52 * on highmem page vectors
53 */
54#define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx])
55
56/* multi-page (mp_bvec) helpers */
57#define mp_bvec_iter_page(bvec, iter) \
58 (__bvec_iter_bvec((bvec), (iter))->bv_page)
59
60#define mp_bvec_iter_len(bvec, iter) \
61 min((iter).bi_size, \
62 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
63
64#define mp_bvec_iter_offset(bvec, iter) \
65 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
66
67#define mp_bvec_iter_page_idx(bvec, iter) \
68 (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
69
70#define mp_bvec_iter_bvec(bvec, iter) \
71((struct bio_vec) { \
72 .bv_page = mp_bvec_iter_page((bvec), (iter)), \
73 .bv_len = mp_bvec_iter_len((bvec), (iter)), \
74 .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \
75})
76
77/* For building single-page bvec in flight */
78 #define bvec_iter_offset(bvec, iter) \
79 (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
80
81#define bvec_iter_len(bvec, iter) \
82 min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \
83 PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
84
85#define bvec_iter_page(bvec, iter) \
86 (mp_bvec_iter_page((bvec), (iter)) + \
87 mp_bvec_iter_page_idx((bvec), (iter)))
88
89#define bvec_iter_bvec(bvec, iter) \
90((struct bio_vec) { \
91 .bv_page = bvec_iter_page((bvec), (iter)), \
92 .bv_len = bvec_iter_len((bvec), (iter)), \
93 .bv_offset = bvec_iter_offset((bvec), (iter)), \
94})
95
96static inline bool bvec_iter_advance(const struct bio_vec *bv,
97 struct bvec_iter *iter, unsigned bytes)
98{
99 unsigned int idx = iter->bi_idx;
100
101 if (WARN_ONCE(bytes > iter->bi_size,
102 "Attempted to advance past end of bvec iter\n")) {
103 iter->bi_size = 0;
104 return false;
105 }
106
107 iter->bi_size -= bytes;
108 bytes += iter->bi_bvec_done;
109
110 while (bytes && bytes >= bv[idx].bv_len) {
111 bytes -= bv[idx].bv_len;
112 idx++;
113 }
114
115 iter->bi_idx = idx;
116 iter->bi_bvec_done = bytes;
117 return true;
118}
119
120static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter)
121{
122 iter->bi_bvec_done = 0;
123 iter->bi_idx++;
124}
125
126#define for_each_bvec(bvl, bio_vec, iter, start) \
127 for (iter = (start); \
128 (iter).bi_size && \
129 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
130 (bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \
131 (bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter)))
132
133/* for iterating one bio from start to end */
134#define BVEC_ITER_ALL_INIT (struct bvec_iter) \
135{ \
136 .bi_sector = 0, \
137 .bi_size = UINT_MAX, \
138 .bi_idx = 0, \
139 .bi_bvec_done = 0, \
140}
141
142static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
143{
144 iter_all->done = 0;
145 iter_all->idx = 0;
146
147 return &iter_all->bv;
148}
149
150static inline void bvec_advance(const struct bio_vec *bvec,
151 struct bvec_iter_all *iter_all)
152{
153 struct bio_vec *bv = &iter_all->bv;
154
155 if (iter_all->done) {
156 bv->bv_page++;
157 bv->bv_offset = 0;
158 } else {
159 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
160 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
161 }
162 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
163 bvec->bv_len - iter_all->done);
164 iter_all->done += bv->bv_len;
165
166 if (iter_all->done == bvec->bv_len) {
167 iter_all->idx++;
168 iter_all->done = 0;
169 }
170}
171
172#endif /* __LINUX_BVEC_ITER_H */