1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * bvec iterator 4 * 5 * Copyright (C) 2001 Ming Lei <[email protected]> 6 */ 7 #ifndef __LINUX_BVEC_ITER_H 8 #define __LINUX_BVEC_ITER_H 9 10 #include <linux/bug.h> 11 #include <linux/errno.h> 12 #include <linux/limits.h> 13 #include <linux/minmax.h> 14 #include <linux/mm.h> 15 #include <linux/types.h> 16 17 struct 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 */ 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_bvec_done; /* number of bytes completed in 45 current bvec */ 46 }; 47 48 struct bvec_iter_all { 49 struct bio_vec bv; 50 int idx; 51 unsigned done; 52 }; 53 54 /* 55 * various member access, note that bio_data should of course not be used 56 * on highmem page vectors 57 */ 58 #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) 59 60 /* multi-page (mp_bvec) helpers */ 61 #define mp_bvec_iter_page(bvec, iter) \ 62 (__bvec_iter_bvec((bvec), (iter))->bv_page) 63 64 #define mp_bvec_iter_len(bvec, iter) \ 65 min((iter).bi_size, \ 66 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done) 67 68 #define mp_bvec_iter_offset(bvec, iter) \ 69 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) 70 71 #define mp_bvec_iter_page_idx(bvec, iter) \ 72 (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE) 73 74 #define mp_bvec_iter_bvec(bvec, iter) \ 75 ((struct bio_vec) { \ 76 .bv_page = mp_bvec_iter_page((bvec), (iter)), \ 77 .bv_len = mp_bvec_iter_len((bvec), (iter)), \ 78 .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \ 79 }) 80 81 /* For building single-page bvec in flight */ 82 #define bvec_iter_offset(bvec, iter) \ 83 (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE) 84 85 #define bvec_iter_len(bvec, iter) \ 86 min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \ 87 PAGE_SIZE - bvec_iter_offset((bvec), (iter))) 88 89 #define bvec_iter_page(bvec, iter) \ 90 (mp_bvec_iter_page((bvec), (iter)) + \ 91 mp_bvec_iter_page_idx((bvec), (iter))) 92 93 #define bvec_iter_bvec(bvec, iter) \ 94 ((struct bio_vec) { \ 95 .bv_page = bvec_iter_page((bvec), (iter)), \ 96 .bv_len = bvec_iter_len((bvec), (iter)), \ 97 .bv_offset = bvec_iter_offset((bvec), (iter)), \ 98 }) 99 100 static inline bool bvec_iter_advance(const struct bio_vec *bv, 101 struct bvec_iter *iter, unsigned bytes) 102 { 103 unsigned int idx = iter->bi_idx; 104 105 if (WARN_ONCE(bytes > iter->bi_size, 106 "Attempted to advance past end of bvec iter\n")) { 107 iter->bi_size = 0; 108 return false; 109 } 110 111 iter->bi_size -= bytes; 112 bytes += iter->bi_bvec_done; 113 114 while (bytes && bytes >= bv[idx].bv_len) { 115 bytes -= bv[idx].bv_len; 116 idx++; 117 } 118 119 iter->bi_idx = idx; 120 iter->bi_bvec_done = bytes; 121 return true; 122 } 123 124 /* 125 * A simpler version of bvec_iter_advance(), @bytes should not span 126 * across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len 127 */ 128 static inline void bvec_iter_advance_single(const struct bio_vec *bv, 129 struct bvec_iter *iter, unsigned int bytes) 130 { 131 unsigned int done = iter->bi_bvec_done + bytes; 132 133 if (done == bv[iter->bi_idx].bv_len) { 134 done = 0; 135 iter->bi_idx++; 136 } 137 iter->bi_bvec_done = done; 138 iter->bi_size -= bytes; 139 } 140 141 #define for_each_bvec(bvl, bio_vec, iter, start) \ 142 for (iter = (start); \ 143 (iter).bi_size && \ 144 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \ 145 bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len)) 146 147 /* for iterating one bio from start to end */ 148 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \ 149 { \ 150 .bi_sector = 0, \ 151 .bi_size = UINT_MAX, \ 152 .bi_idx = 0, \ 153 .bi_bvec_done = 0, \ 154 } 155 156 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all) 157 { 158 iter_all->done = 0; 159 iter_all->idx = 0; 160 161 return &iter_all->bv; 162 } 163 164 static inline void bvec_advance(const struct bio_vec *bvec, 165 struct bvec_iter_all *iter_all) 166 { 167 struct bio_vec *bv = &iter_all->bv; 168 169 if (iter_all->done) { 170 bv->bv_page++; 171 bv->bv_offset = 0; 172 } else { 173 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT); 174 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK; 175 } 176 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset, 177 bvec->bv_len - iter_all->done); 178 iter_all->done += bv->bv_len; 179 180 if (iter_all->done == bvec->bv_len) { 181 iter_all->idx++; 182 iter_all->done = 0; 183 } 184 } 185 186 #endif /* __LINUX_BVEC_ITER_H */ 187