1 /*
2 * bvec iterator
3 *
4 * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 *
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public Licens
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-
19 */
20 #ifndef __LINUX_BVEC_ITER_H
21 #define __LINUX_BVEC_ITER_H
22
23 #include <linux/kernel.h>
24 #include <linux/bug.h>
25 #include <linux/errno.h>
26
27 /*
28 * was unsigned short, but we might as well be ready for > 64kB I/O pages
29 */
30 struct bio_vec {
31 struct page *bv_page;
32 unsigned int bv_len;
33 unsigned int bv_offset;
34 };
35
36 struct bvec_iter {
37 sector_t bi_sector; /* device address in 512 byte
38 sectors */
39 unsigned int bi_size; /* residual I/O count */
40
41 unsigned int bi_idx; /* current index into bvl_vec */
42
43 unsigned int bi_done; /* number of bytes completed */
44
45 unsigned int bi_bvec_done; /* number of bytes completed in
46 current bvec */
47 };
48
49 /*
50 * various member access, note that bio_data should of course not be used
51 * on highmem page vectors
52 */
53 #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx])
54
55 #define bvec_iter_page(bvec, iter) \
56 (__bvec_iter_bvec((bvec), (iter))->bv_page)
57
58 #define bvec_iter_len(bvec, iter) \
59 min((iter).bi_size, \
60 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
61
62 #define bvec_iter_offset(bvec, iter) \
63 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
64
65 #define bvec_iter_bvec(bvec, iter) \
66 ((struct bio_vec) { \
67 .bv_page = bvec_iter_page((bvec), (iter)), \
68 .bv_len = bvec_iter_len((bvec), (iter)), \
69 .bv_offset = bvec_iter_offset((bvec), (iter)), \
70 })
71
bvec_iter_advance(const struct bio_vec * bv,struct bvec_iter * iter,unsigned bytes)72 static inline bool bvec_iter_advance(const struct bio_vec *bv,
73 struct bvec_iter *iter, unsigned bytes)
74 {
75 if (WARN_ONCE(bytes > iter->bi_size,
76 "Attempted to advance past end of bvec iter\n")) {
77 iter->bi_size = 0;
78 return false;
79 }
80
81 while (bytes) {
82 unsigned iter_len = bvec_iter_len(bv, *iter);
83 unsigned len = min(bytes, iter_len);
84
85 bytes -= len;
86 iter->bi_size -= len;
87 iter->bi_bvec_done += len;
88 iter->bi_done += len;
89
90 if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
91 iter->bi_bvec_done = 0;
92 iter->bi_idx++;
93 }
94 }
95 return true;
96 }
97
bvec_iter_rewind(const struct bio_vec * bv,struct bvec_iter * iter,unsigned int bytes)98 static inline bool bvec_iter_rewind(const struct bio_vec *bv,
99 struct bvec_iter *iter,
100 unsigned int bytes)
101 {
102 while (bytes) {
103 unsigned len = min(bytes, iter->bi_bvec_done);
104
105 if (iter->bi_bvec_done == 0) {
106 if (WARN_ONCE(iter->bi_idx == 0,
107 "Attempted to rewind iter beyond "
108 "bvec's boundaries\n")) {
109 return false;
110 }
111 iter->bi_idx--;
112 iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len;
113 continue;
114 }
115 bytes -= len;
116 iter->bi_size += len;
117 iter->bi_bvec_done -= len;
118 }
119 return true;
120 }
121
122 #define for_each_bvec(bvl, bio_vec, iter, start) \
123 for (iter = (start); \
124 (iter).bi_size && \
125 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
126 bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
127
128 /* for iterating one bio from start to end */
129 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \
130 { \
131 .bi_sector = 0, \
132 .bi_size = UINT_MAX, \
133 .bi_idx = 0, \
134 .bi_bvec_done = 0, \
135 }
136
137 #endif /* __LINUX_BVEC_ITER_H */
138
