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