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_H
8 #define __LINUX_BVEC_H
9
10 #include <linux/highmem.h>
11 #include <linux/bug.h>
12 #include <linux/errno.h>
13 #include <linux/limits.h>
14 #include <linux/minmax.h>
15 #include <linux/mm.h>
16 #include <linux/types.h>
17
18 struct page;
19
20 /**
21 * struct bio_vec - a contiguous range of physical memory addresses
22 * @bv_page: First page associated with the address range.
23 * @bv_len: Number of bytes in the address range.
24 * @bv_offset: Start of the address range relative to the start of @bv_page.
25 *
26 * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
27 *
28 * nth_page(@bv_page, n) == @bv_page + n
29 *
30 * This holds because page_is_mergeable() checks the above property.
31 */
32 struct bio_vec {
33 struct page *bv_page;
34 unsigned int bv_len;
35 unsigned int bv_offset;
36 };
37
38 /**
39 * bvec_set_page - initialize a bvec based off a struct page
40 * @bv: bvec to initialize
41 * @page: page the bvec should point to
42 * @len: length of the bvec
43 * @offset: offset into the page
44 */
bvec_set_page(struct bio_vec * bv,struct page * page,unsigned int len,unsigned int offset)45 static inline void bvec_set_page(struct bio_vec *bv, struct page *page,
46 unsigned int len, unsigned int offset)
47 {
48 bv->bv_page = page;
49 bv->bv_len = len;
50 bv->bv_offset = offset;
51 }
52
53 struct bvec_iter {
54 sector_t bi_sector; /* device address in 512 byte
55 sectors */
56 unsigned int bi_size; /* residual I/O count */
57
58 unsigned int bi_idx; /* current index into bvl_vec */
59
60 unsigned int bi_bvec_done; /* number of bytes completed in
61 current bvec */
62 } __packed;
63
64 struct bvec_iter_all {
65 struct bio_vec bv;
66 int idx;
67 unsigned done;
68 };
69
70 /*
71 * various member access, note that bio_data should of course not be used
72 * on highmem page vectors
73 */
74 #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx])
75
76 /* multi-page (mp_bvec) helpers */
77 #define mp_bvec_iter_page(bvec, iter) \
78 (__bvec_iter_bvec((bvec), (iter))->bv_page)
79
80 #define mp_bvec_iter_len(bvec, iter) \
81 min((iter).bi_size, \
82 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
83
84 #define mp_bvec_iter_offset(bvec, iter) \
85 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
86
87 #define mp_bvec_iter_page_idx(bvec, iter) \
88 (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
89
90 #define mp_bvec_iter_bvec(bvec, iter) \
91 ((struct bio_vec) { \
92 .bv_page = mp_bvec_iter_page((bvec), (iter)), \
93 .bv_len = mp_bvec_iter_len((bvec), (iter)), \
94 .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \
95 })
96
97 /* For building single-page bvec in flight */
98 #define bvec_iter_offset(bvec, iter) \
99 (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
100
101 #define bvec_iter_len(bvec, iter) \
102 min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \
103 PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
104
105 #define bvec_iter_page(bvec, iter) \
106 (mp_bvec_iter_page((bvec), (iter)) + \
107 mp_bvec_iter_page_idx((bvec), (iter)))
108
109 #define bvec_iter_bvec(bvec, iter) \
110 ((struct bio_vec) { \
111 .bv_page = bvec_iter_page((bvec), (iter)), \
112 .bv_len = bvec_iter_len((bvec), (iter)), \
113 .bv_offset = bvec_iter_offset((bvec), (iter)), \
114 })
115
bvec_iter_advance(const struct bio_vec * bv,struct bvec_iter * iter,unsigned bytes)116 static inline bool bvec_iter_advance(const struct bio_vec *bv,
117 struct bvec_iter *iter, unsigned bytes)
118 {
119 unsigned int idx = iter->bi_idx;
120
121 if (WARN_ONCE(bytes > iter->bi_size,
122 "Attempted to advance past end of bvec iter\n")) {
123 iter->bi_size = 0;
124 return false;
125 }
126
127 iter->bi_size -= bytes;
128 bytes += iter->bi_bvec_done;
129
130 while (bytes && bytes >= bv[idx].bv_len) {
131 bytes -= bv[idx].bv_len;
132 idx++;
133 }
134
135 iter->bi_idx = idx;
136 iter->bi_bvec_done = bytes;
137 return true;
138 }
139
140 /*
141 * A simpler version of bvec_iter_advance(), @bytes should not span
142 * across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len
143 */
bvec_iter_advance_single(const struct bio_vec * bv,struct bvec_iter * iter,unsigned int bytes)144 static inline void bvec_iter_advance_single(const struct bio_vec *bv,
145 struct bvec_iter *iter, unsigned int bytes)
146 {
147 unsigned int done = iter->bi_bvec_done + bytes;
148
149 if (done == bv[iter->bi_idx].bv_len) {
150 done = 0;
151 iter->bi_idx++;
152 }
153 iter->bi_bvec_done = done;
154 iter->bi_size -= bytes;
155 }
156
157 #define for_each_bvec(bvl, bio_vec, iter, start) \
158 for (iter = (start); \
159 (iter).bi_size && \
160 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
161 bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len))
162
163 /* for iterating one bio from start to end */
164 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \
165 { \
166 .bi_sector = 0, \
167 .bi_size = UINT_MAX, \
168 .bi_idx = 0, \
169 .bi_bvec_done = 0, \
170 }
171
bvec_init_iter_all(struct bvec_iter_all * iter_all)172 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
173 {
174 iter_all->done = 0;
175 iter_all->idx = 0;
176
177 return &iter_all->bv;
178 }
179
bvec_advance(const struct bio_vec * bvec,struct bvec_iter_all * iter_all)180 static inline void bvec_advance(const struct bio_vec *bvec,
181 struct bvec_iter_all *iter_all)
182 {
183 struct bio_vec *bv = &iter_all->bv;
184
185 if (iter_all->done) {
186 bv->bv_page++;
187 bv->bv_offset = 0;
188 } else {
189 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
190 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
191 }
192 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
193 bvec->bv_len - iter_all->done);
194 iter_all->done += bv->bv_len;
195
196 if (iter_all->done == bvec->bv_len) {
197 iter_all->idx++;
198 iter_all->done = 0;
199 }
200 }
201
202 /**
203 * bvec_kmap_local - map a bvec into the kernel virtual address space
204 * @bvec: bvec to map
205 *
206 * Must be called on single-page bvecs only. Call kunmap_local on the returned
207 * address to unmap.
208 */
bvec_kmap_local(struct bio_vec * bvec)209 static inline void *bvec_kmap_local(struct bio_vec *bvec)
210 {
211 return kmap_local_page(bvec->bv_page) + bvec->bv_offset;
212 }
213
214 /**
215 * memcpy_from_bvec - copy data from a bvec
216 * @bvec: bvec to copy from
217 *
218 * Must be called on single-page bvecs only.
219 */
memcpy_from_bvec(char * to,struct bio_vec * bvec)220 static inline void memcpy_from_bvec(char *to, struct bio_vec *bvec)
221 {
222 memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, bvec->bv_len);
223 }
224
225 /**
226 * memcpy_to_bvec - copy data to a bvec
227 * @bvec: bvec to copy to
228 *
229 * Must be called on single-page bvecs only.
230 */
memcpy_to_bvec(struct bio_vec * bvec,const char * from)231 static inline void memcpy_to_bvec(struct bio_vec *bvec, const char *from)
232 {
233 memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, bvec->bv_len);
234 }
235
236 /**
237 * memzero_bvec - zero all data in a bvec
238 * @bvec: bvec to zero
239 *
240 * Must be called on single-page bvecs only.
241 */
memzero_bvec(struct bio_vec * bvec)242 static inline void memzero_bvec(struct bio_vec *bvec)
243 {
244 memzero_page(bvec->bv_page, bvec->bv_offset, bvec->bv_len);
245 }
246
247 /**
248 * bvec_virt - return the virtual address for a bvec
249 * @bvec: bvec to return the virtual address for
250 *
251 * Note: the caller must ensure that @bvec->bv_page is not a highmem page.
252 */
bvec_virt(struct bio_vec * bvec)253 static inline void *bvec_virt(struct bio_vec *bvec)
254 {
255 WARN_ON_ONCE(PageHighMem(bvec->bv_page));
256 return page_address(bvec->bv_page) + bvec->bv_offset;
257 }
258
259 #endif /* __LINUX_BVEC_H */
260