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
17struct 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 */
31struct 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 */
44static 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 */
59static 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 */
71static 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
77struct 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
88struct 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
140static 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 */
168static 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
196static 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
204static 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 */
233static 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 */
244static 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 */
255static 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 */
266static 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 */
277static 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