bvec.h

  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 * All pages within a bio_vec starting from @bv_page are contiguous and
 26 * can simply be iterated (see bvec_advance()).
 27 */
 28struct bio_vec {
 29	struct page	*bv_page;
 30	unsigned int	bv_len;
 31	unsigned int	bv_offset;
 32};
 33
 34/**
 35 * bvec_set_page - initialize a bvec based off a struct page
 36 * @bv:		bvec to initialize
 37 * @page:	page the bvec should point to
 38 * @len:	length of the bvec
 39 * @offset:	offset into the page
 40 */
 41static inline void bvec_set_page(struct bio_vec *bv, struct page *page,
 42		unsigned int len, unsigned int offset)
 43{
 44	bv->bv_page = page;
 45	bv->bv_len = len;
 46	bv->bv_offset = offset;
 47}
 48
 49/**
 50 * bvec_set_folio - initialize a bvec based off a struct folio
 51 * @bv:		bvec to initialize
 52 * @folio:	folio the bvec should point to
 53 * @len:	length of the bvec
 54 * @offset:	offset into the folio
 55 */
 56static inline void bvec_set_folio(struct bio_vec *bv, struct folio *folio,
 57		size_t len, size_t offset)
 58{
 59	unsigned long nr = offset / PAGE_SIZE;
 60
 61	WARN_ON_ONCE(len > UINT_MAX);
 62	bvec_set_page(bv, folio_page(folio, nr), len, offset % PAGE_SIZE);
 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#define for_each_mp_bvec(bvl, bio_vec, iter, start)			\
188	for (iter = (start);						\
189	     (iter).bi_size &&						\
190		((bvl = mp_bvec_iter_bvec((bio_vec), (iter))), 1);	\
191	     bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len))
192
193/* for iterating one bio from start to end */
194#define BVEC_ITER_ALL_INIT (struct bvec_iter)				\
195{									\
196	.bi_sector	= 0,						\
197	.bi_size	= UINT_MAX,					\
198	.bi_idx		= 0,						\
199	.bi_bvec_done	= 0,						\
200}
201
202static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
203{
204	iter_all->done = 0;
205	iter_all->idx = 0;
206
207	return &iter_all->bv;
208}
209
210static inline void bvec_advance(const struct bio_vec *bvec,
211				struct bvec_iter_all *iter_all)
212{
213	struct bio_vec *bv = &iter_all->bv;
214
215	if (iter_all->done) {
216		bv->bv_page++;
217		bv->bv_offset = 0;
218	} else {
219		bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
220		bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
221	}
222	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
223			   bvec->bv_len - iter_all->done);
224	iter_all->done += bv->bv_len;
225
226	if (iter_all->done == bvec->bv_len) {
227		iter_all->idx++;
228		iter_all->done = 0;
229	}
230}
231
232/**
233 * bvec_kmap_local - map a bvec into the kernel virtual address space
234 * @bvec: bvec to map
235 *
236 * Must be called on single-page bvecs only.  Call kunmap_local on the returned
237 * address to unmap.
238 */
239static inline void *bvec_kmap_local(struct bio_vec *bvec)
240{
241	return kmap_local_page(bvec->bv_page) + bvec->bv_offset;
242}
243
244/**
245 * memcpy_from_bvec - copy data from a bvec
246 * @bvec: bvec to copy from
247 *
248 * Must be called on single-page bvecs only.
249 */
250static inline void memcpy_from_bvec(char *to, struct bio_vec *bvec)
251{
252	memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, bvec->bv_len);
253}
254
255/**
256 * memcpy_to_bvec - copy data to a bvec
257 * @bvec: bvec to copy to
258 *
259 * Must be called on single-page bvecs only.
260 */
261static inline void memcpy_to_bvec(struct bio_vec *bvec, const char *from)
262{
263	memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, bvec->bv_len);
264}
265
266/**
267 * memzero_bvec - zero all data in a bvec
268 * @bvec: bvec to zero
269 *
270 * Must be called on single-page bvecs only.
271 */
272static inline void memzero_bvec(struct bio_vec *bvec)
273{
274	memzero_page(bvec->bv_page, bvec->bv_offset, bvec->bv_len);
275}
276
277/**
278 * bvec_virt - return the virtual address for a bvec
279 * @bvec: bvec to return the virtual address for
280 *
281 * Note: the caller must ensure that @bvec->bv_page is not a highmem page.
282 */
283static inline void *bvec_virt(struct bio_vec *bvec)
284{
285	WARN_ON_ONCE(PageHighMem(bvec->bv_page));
286	return page_address(bvec->bv_page) + bvec->bv_offset;
287}
288
289/**
290 * bvec_phys - return the physical address for a bvec
291 * @bvec: bvec to return the physical address for
292 */
293static inline phys_addr_t bvec_phys(const struct bio_vec *bvec)
294{
295	return page_to_phys(bvec->bv_page) + bvec->bv_offset;
296}
297
298#endif /* __LINUX_BVEC_H */