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/types.h>
16
17 struct page;
18
19 /**
20 * struct bio_vec - a contiguous range of physical memory addresses
21 * @bv_page: First page associated with the address range.
22 * @bv_len: Number of bytes in the address range.
23 * @bv_offset: Start of the address range relative to the start of @bv_page.
24 *
25 * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
26 *
27 * nth_page(@bv_page, n) == @bv_page + n
28 *
29 * This holds because page_is_mergeable() checks the above property.
30 */
31 struct bio_vec {
32 struct page *bv_page;
33 unsigned int bv_len;
34 unsigned int bv_offset;
35 };
36
37 /**
38 * bvec_set_page - initialize a bvec based off a struct page
39 * @bv: bvec to initialize
40 * @page: page the bvec should point to
41 * @len: length of the bvec
42 * @offset: offset into the page
43 */
44 static inline void bvec_set_page(struct bio_vec *bv, struct page *page,
45 unsigned int len, unsigned int offset)
46 {
47 bv->bv_page = page;
48 bv->bv_len = len;
49 bv->bv_offset = offset;
50 }
51
52 /**
53 * bvec_set_folio - initialize a bvec based off a struct folio
54 * @bv: bvec to initialize
55 * @folio: folio the bvec should point to
56 * @len: length of the bvec
57 * @offset: offset into the folio
58 */
59 static inline void bvec_set_folio(struct bio_vec *bv, struct folio *folio,
60 unsigned int len, unsigned int offset)
61 {
62 bvec_set_page(bv, &folio->page, len, offset);
63 }
64
65 /**
66 * bvec_set_virt - initialize a bvec based on a virtual address
67 * @bv: bvec to initialize
68 * @vaddr: virtual address to set the bvec to
69 * @len: length of the bvec
70 */
71 static inline void bvec_set_virt(struct bio_vec *bv, void *vaddr,
72 unsigned int len)
73 {
74 bvec_set_page(bv, virt_to_page(vaddr), len, offset_in_page(vaddr));
75 }
76
77 struct bvec_iter {
78 sector_t bi_sector; /* device address in 512 byte
79 sectors */
80 unsigned int bi_size; /* residual I/O count */
81
82 unsigned int bi_idx; /* current index into bvl_vec */
83
84 unsigned int bi_bvec_done; /* number of bytes completed in
85 current bvec */
86 } __packed __aligned(4);
87
88 struct bvec_iter_all {
89 struct bio_vec bv;
90 int idx;
91 unsigned done;
92 };
93
94 /*
95 * various member access, note that bio_data should of course not be used
96 * on highmem page vectors
97 */
98 #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx])
99
100 /* multi-page (mp_bvec) helpers */
101 #define mp_bvec_iter_page(bvec, iter) \
102 (__bvec_iter_bvec((bvec), (iter))->bv_page)
103
104 #define mp_bvec_iter_len(bvec, iter) \
105 min((iter).bi_size, \
106 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
107
108 #define mp_bvec_iter_offset(bvec, iter) \
109 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
110
111 #define mp_bvec_iter_page_idx(bvec, iter) \
112 (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
113
114 #define mp_bvec_iter_bvec(bvec, iter) \
115 ((struct bio_vec) { \
116 .bv_page = mp_bvec_iter_page((bvec), (iter)), \
117 .bv_len = mp_bvec_iter_len((bvec), (iter)), \
118 .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \
119 })
120
121 /* For building single-page bvec in flight */
122 #define bvec_iter_offset(bvec, iter) \
123 (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
124
125 #define bvec_iter_len(bvec, iter) \
126 min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \
127 PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
128
129 #define bvec_iter_page(bvec, iter) \
130 (mp_bvec_iter_page((bvec), (iter)) + \
131 mp_bvec_iter_page_idx((bvec), (iter)))
132
133 #define bvec_iter_bvec(bvec, iter) \
134 ((struct bio_vec) { \
135 .bv_page = bvec_iter_page((bvec), (iter)), \
136 .bv_len = bvec_iter_len((bvec), (iter)), \
137 .bv_offset = bvec_iter_offset((bvec), (iter)), \
138 })
139
140 static inline bool bvec_iter_advance(const struct bio_vec *bv,
141 struct bvec_iter *iter, unsigned bytes)
142 {
143 unsigned int idx = iter->bi_idx;
144
145 if (WARN_ONCE(bytes > iter->bi_size,
146 "Attempted to advance past end of bvec iter\n")) {
147 iter->bi_size = 0;
148 return false;
149 }
150
151 iter->bi_size -= bytes;
152 bytes += iter->bi_bvec_done;
153
154 while (bytes && bytes >= bv[idx].bv_len) {
155 bytes -= bv[idx].bv_len;
156 idx++;
157 }
158
159 iter->bi_idx = idx;
160 iter->bi_bvec_done = bytes;
161 return true;
162 }
163
164 /*
165 * A simpler version of bvec_iter_advance(), @bytes should not span
166 * across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len
167 */
168 static inline void bvec_iter_advance_single(const struct bio_vec *bv,
169 struct bvec_iter *iter, unsigned int bytes)
170 {
171 unsigned int done = iter->bi_bvec_done + bytes;
172
173 if (done == bv[iter->bi_idx].bv_len) {
174 done = 0;
175 iter->bi_idx++;
176 }
177 iter->bi_bvec_done = done;
178 iter->bi_size -= bytes;
179 }
180
181 #define for_each_bvec(bvl, bio_vec, iter, start) \
182 for (iter = (start); \
183 (iter).bi_size && \
184 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
185 bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len))
186
187 /* for iterating one bio from start to end */
188 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \
189 { \
190 .bi_sector = 0, \
191 .bi_size = UINT_MAX, \
192 .bi_idx = 0, \
193 .bi_bvec_done = 0, \
194 }
195
196 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
197 {
198 iter_all->done = 0;
199 iter_all->idx = 0;
200
201 return &iter_all->bv;
202 }
203
204 static inline void bvec_advance(const struct bio_vec *bvec,
205 struct bvec_iter_all *iter_all)
206 {
207 struct bio_vec *bv = &iter_all->bv;
208
209 if (iter_all->done) {
210 bv->bv_page++;
211 bv->bv_offset = 0;
212 } else {
213 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
214 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
215 }
216 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
217 bvec->bv_len - iter_all->done);
218 iter_all->done += bv->bv_len;
219
220 if (iter_all->done == bvec->bv_len) {
221 iter_all->idx++;
222 iter_all->done = 0;
223 }
224 }
225
226 /**
227 * bvec_kmap_local - map a bvec into the kernel virtual address space
228 * @bvec: bvec to map
229 *
230 * Must be called on single-page bvecs only. Call kunmap_local on the returned
231 * address to unmap.
232 */
233 static inline void *bvec_kmap_local(struct bio_vec *bvec)
234 {
235 return kmap_local_page(bvec->bv_page) + bvec->bv_offset;
236 }
237
238 /**
239 * memcpy_from_bvec - copy data from a bvec
240 * @bvec: bvec to copy from
241 *
242 * Must be called on single-page bvecs only.
243 */
244 static inline void memcpy_from_bvec(char *to, struct bio_vec *bvec)
245 {
246 memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, bvec->bv_len);
247 }
248
249 /**
250 * memcpy_to_bvec - copy data to a bvec
251 * @bvec: bvec to copy to
252 *
253 * Must be called on single-page bvecs only.
254 */
255 static inline void memcpy_to_bvec(struct bio_vec *bvec, const char *from)
256 {
257 memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, bvec->bv_len);
258 }
259
260 /**
261 * memzero_bvec - zero all data in a bvec
262 * @bvec: bvec to zero
263 *
264 * Must be called on single-page bvecs only.
265 */
266 static inline void memzero_bvec(struct bio_vec *bvec)
267 {
268 memzero_page(bvec->bv_page, bvec->bv_offset, bvec->bv_len);
269 }
270
271 /**
272 * bvec_virt - return the virtual address for a bvec
273 * @bvec: bvec to return the virtual address for
274 *
275 * Note: the caller must ensure that @bvec->bv_page is not a highmem page.
276 */
277 static inline void *bvec_virt(struct bio_vec *bvec)
278 {
279 WARN_ON_ONCE(PageHighMem(bvec->bv_page));
280 return page_address(bvec->bv_page) + bvec->bv_offset;
281 }
282
283 /**
284 * bvec_phys - return the physical address for a bvec
285 * @bvec: bvec to return the physical address for
286 */
287 static inline phys_addr_t bvec_phys(const struct bio_vec *bvec)
288 {
289 /*
290 * Note this open codes page_to_phys because page_to_phys is defined in
291 * <asm/io.h>, which we don't want to pull in here. If it ever moves to
292 * a sensible place we should start using it.
293 */
294 return PFN_PHYS(page_to_pfn(bvec->bv_page)) + bvec->bv_offset;
295 }
296
297 #endif /* __LINUX_BVEC_H */
298
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