GNU Linux-libre 4.19.207-gnu1
[releases.git] / include / linux / bvec.h
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
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
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 static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter)
123 {
124         iter->bi_bvec_done = 0;
125         iter->bi_idx++;
126 }
127
128 #define for_each_bvec(bvl, bio_vec, iter, start)                        \
129         for (iter = (start);                                            \
130              (iter).bi_size &&                                          \
131                 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
132              (bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \
133                      (bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter)))
134
135 /* for iterating one bio from start to end */
136 #define BVEC_ITER_ALL_INIT (struct bvec_iter)                           \
137 {                                                                       \
138         .bi_sector      = 0,                                            \
139         .bi_size        = UINT_MAX,                                     \
140         .bi_idx         = 0,                                            \
141         .bi_bvec_done   = 0,                                            \
142 }
143
144 #endif /* __LINUX_BVEC_ITER_H */