GNU Linux-libre 4.14.294-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 #include <linux/mm.h>
27
28 /*
29  * was unsigned short, but we might as well be ready for > 64kB I/O pages
30  */
31 struct bio_vec {
32         struct page     *bv_page;
33         unsigned int    bv_len;
34         unsigned int    bv_offset;
35 };
36
37 struct bvec_iter {
38         sector_t                bi_sector;      /* device address in 512 byte
39                                                    sectors */
40         unsigned int            bi_size;        /* residual I/O count */
41
42         unsigned int            bi_idx;         /* current index into bvl_vec */
43
44         unsigned int            bi_done;        /* number of bytes completed */
45
46         unsigned int            bi_bvec_done;   /* number of bytes completed in
47                                                    current bvec */
48 };
49
50 /*
51  * various member access, note that bio_data should of course not be used
52  * on highmem page vectors
53  */
54 #define __bvec_iter_bvec(bvec, iter)    (&(bvec)[(iter).bi_idx])
55
56 /* multi-page (mp_bvec) helpers */
57 #define mp_bvec_iter_page(bvec, iter)                           \
58         (__bvec_iter_bvec((bvec), (iter))->bv_page)
59
60 #define mp_bvec_iter_len(bvec, iter)                            \
61         min((iter).bi_size,                                     \
62             __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
63
64 #define mp_bvec_iter_offset(bvec, iter)                         \
65         (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
66
67 #define mp_bvec_iter_page_idx(bvec, iter)                       \
68         (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
69
70 #define mp_bvec_iter_bvec(bvec, iter)                           \
71 ((struct bio_vec) {                                             \
72         .bv_page        = mp_bvec_iter_page((bvec), (iter)),    \
73         .bv_len         = mp_bvec_iter_len((bvec), (iter)),     \
74         .bv_offset      = mp_bvec_iter_offset((bvec), (iter)),  \
75 })
76
77 /* For building single-page bvec in flight */
78  #define bvec_iter_offset(bvec, iter)                           \
79         (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
80
81 #define bvec_iter_len(bvec, iter)                               \
82         min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),               \
83               PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
84
85 #define bvec_iter_page(bvec, iter)                              \
86         nth_page(mp_bvec_iter_page((bvec), (iter)),             \
87                  mp_bvec_iter_page_idx((bvec), (iter)))
88
89 #define bvec_iter_bvec(bvec, iter)                              \
90 ((struct bio_vec) {                                             \
91         .bv_page        = bvec_iter_page((bvec), (iter)),       \
92         .bv_len         = bvec_iter_len((bvec), (iter)),        \
93         .bv_offset      = bvec_iter_offset((bvec), (iter)),     \
94 })
95
96 static inline bool bvec_iter_advance(const struct bio_vec *bv,
97                 struct bvec_iter *iter, unsigned bytes)
98 {
99         if (WARN_ONCE(bytes > iter->bi_size,
100                      "Attempted to advance past end of bvec iter\n")) {
101                 iter->bi_size = 0;
102                 return false;
103         }
104
105         while (bytes) {
106                 unsigned iter_len = bvec_iter_len(bv, *iter);
107                 unsigned len = min(bytes, iter_len);
108
109                 bytes -= len;
110                 iter->bi_size -= len;
111                 iter->bi_bvec_done += len;
112                 iter->bi_done += len;
113
114                 if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
115                         iter->bi_bvec_done = 0;
116                         iter->bi_idx++;
117                 }
118         }
119         return true;
120 }
121
122 static inline bool bvec_iter_rewind(const struct bio_vec *bv,
123                                      struct bvec_iter *iter,
124                                      unsigned int bytes)
125 {
126         while (bytes) {
127                 unsigned len = min(bytes, iter->bi_bvec_done);
128
129                 if (iter->bi_bvec_done == 0) {
130                         if (WARN_ONCE(iter->bi_idx == 0,
131                                       "Attempted to rewind iter beyond "
132                                       "bvec's boundaries\n")) {
133                                 return false;
134                         }
135                         iter->bi_idx--;
136                         iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len;
137                         continue;
138                 }
139                 bytes -= len;
140                 iter->bi_size += len;
141                 iter->bi_bvec_done -= len;
142         }
143         return true;
144 }
145
146 static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter)
147 {
148         iter->bi_bvec_done = 0;
149         iter->bi_idx++;
150 }
151
152 #define for_each_bvec(bvl, bio_vec, iter, start)                        \
153         for (iter = (start);                                            \
154              (iter).bi_size &&                                          \
155                 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
156              (bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \
157                      (bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter)))
158
159 #endif /* __LINUX_BVEC_ITER_H */