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  */
bvec_set_page(struct bio_vec * bv,struct page * page,unsigned int len,unsigned int offset)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  */
bvec_set_folio(struct bio_vec * bv,struct folio * folio,unsigned int len,unsigned int offset)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  */
bvec_set_virt(struct bio_vec * bv,void * vaddr,unsigned int len)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;
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 
bvec_iter_advance(const struct bio_vec * bv,struct bvec_iter * iter,unsigned bytes)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  */
bvec_iter_advance_single(const struct bio_vec * bv,struct bvec_iter * iter,unsigned int bytes)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 
bvec_init_iter_all(struct bvec_iter_all * iter_all)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 
bvec_advance(const struct bio_vec * bvec,struct bvec_iter_all * iter_all)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  */
bvec_kmap_local(struct bio_vec * bvec)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  */
memcpy_from_bvec(char * to,struct bio_vec * bvec)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  */
memcpy_to_bvec(struct bio_vec * bvec,const char * from)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  */
memzero_bvec(struct bio_vec * bvec)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  */
bvec_virt(struct bio_vec * bvec)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 #endif /* __LINUX_BVEC_H */
284