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/kernel.h> 11 #include <linux/bug.h> 12 #include <linux/errno.h> 13 #include <linux/mm.h> 14 15 /* 16 * was unsigned short, but we might as well be ready for > 64kB I/O pages 17 */ 18 struct bio_vec { 19 struct page *bv_page; 20 unsigned int bv_len; 21 unsigned int bv_offset; 22 }; 23 24 struct bvec_iter { 25 sector_t bi_sector; /* device address in 512 byte 26 sectors */ 27 unsigned int bi_size; /* residual I/O count */ 28 29 unsigned int bi_idx; /* current index into bvl_vec */ 30 31 unsigned int bi_bvec_done; /* number of bytes completed in 32 current bvec */ 33 }; 34 35 struct bvec_iter_all { 36 struct bio_vec bv; 37 int idx; 38 unsigned done; 39 }; 40 41 /* 42 * various member access, note that bio_data should of course not be used 43 * on highmem page vectors 44 */ 45 #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) 46 47 /* multi-page (mp_bvec) helpers */ 48 #define mp_bvec_iter_page(bvec, iter) \ 49 (__bvec_iter_bvec((bvec), (iter))->bv_page) 50 51 #define mp_bvec_iter_len(bvec, iter) \ 52 min((iter).bi_size, \ 53 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done) 54 55 #define mp_bvec_iter_offset(bvec, iter) \ 56 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) 57 58 #define mp_bvec_iter_page_idx(bvec, iter) \ 59 (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE) 60 61 #define mp_bvec_iter_bvec(bvec, iter) \ 62 ((struct bio_vec) { \ 63 .bv_page = mp_bvec_iter_page((bvec), (iter)), \ 64 .bv_len = mp_bvec_iter_len((bvec), (iter)), \ 65 .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \ 66 }) 67 68 /* For building single-page bvec in flight */ 69 #define bvec_iter_offset(bvec, iter) \ 70 (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE) 71 72 #define bvec_iter_len(bvec, iter) \ 73 min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \ 74 PAGE_SIZE - bvec_iter_offset((bvec), (iter))) 75 76 #define bvec_iter_page(bvec, iter) \ 77 (mp_bvec_iter_page((bvec), (iter)) + \ 78 mp_bvec_iter_page_idx((bvec), (iter))) 79 80 #define bvec_iter_bvec(bvec, iter) \ 81 ((struct bio_vec) { \ 82 .bv_page = bvec_iter_page((bvec), (iter)), \ 83 .bv_len = bvec_iter_len((bvec), (iter)), \ 84 .bv_offset = bvec_iter_offset((bvec), (iter)), \ 85 }) 86 87 static inline bool bvec_iter_advance(const struct bio_vec *bv, 88 struct bvec_iter *iter, unsigned bytes) 89 { 90 if (WARN_ONCE(bytes > iter->bi_size, 91 "Attempted to advance past end of bvec iter\n")) { 92 iter->bi_size = 0; 93 return false; 94 } 95 96 while (bytes) { 97 const struct bio_vec *cur = bv + iter->bi_idx; 98 unsigned len = min3(bytes, iter->bi_size, 99 cur->bv_len - iter->bi_bvec_done); 100 101 bytes -= len; 102 iter->bi_size -= len; 103 iter->bi_bvec_done += len; 104 105 if (iter->bi_bvec_done == cur->bv_len) { 106 iter->bi_bvec_done = 0; 107 iter->bi_idx++; 108 } 109 } 110 return true; 111 } 112 113 #define for_each_bvec(bvl, bio_vec, iter, start) \ 114 for (iter = (start); \ 115 (iter).bi_size && \ 116 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \ 117 bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len)) 118 119 /* for iterating one bio from start to end */ 120 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \ 121 { \ 122 .bi_sector = 0, \ 123 .bi_size = UINT_MAX, \ 124 .bi_idx = 0, \ 125 .bi_bvec_done = 0, \ 126 } 127 128 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all) 129 { 130 iter_all->done = 0; 131 iter_all->idx = 0; 132 133 return &iter_all->bv; 134 } 135 136 static inline struct page *bvec_nth_page(struct page *page, int idx) 137 { 138 return idx == 0 ? page : nth_page(page, idx); 139 } 140 141 static inline void bvec_advance(const struct bio_vec *bvec, 142 struct bvec_iter_all *iter_all) 143 { 144 struct bio_vec *bv = &iter_all->bv; 145 146 if (iter_all->done) { 147 bv->bv_page++; 148 bv->bv_offset = 0; 149 } else { 150 bv->bv_page = bvec_nth_page(bvec->bv_page, bvec->bv_offset / 151 PAGE_SIZE); 152 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK; 153 } 154 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset, 155 bvec->bv_len - iter_all->done); 156 iter_all->done += bv->bv_len; 157 158 if (iter_all->done == bvec->bv_len) { 159 iter_all->idx++; 160 iter_all->done = 0; 161 } 162 } 163 164 /* 165 * Get the last single-page segment from the multi-page bvec and store it 166 * in @seg 167 */ 168 static inline void mp_bvec_last_segment(const struct bio_vec *bvec, 169 struct bio_vec *seg) 170 { 171 unsigned total = bvec->bv_offset + bvec->bv_len; 172 unsigned last_page = (total - 1) / PAGE_SIZE; 173 174 seg->bv_page = bvec->bv_page + last_page; 175 176 /* the whole segment is inside the last page */ 177 if (bvec->bv_offset >= last_page * PAGE_SIZE) { 178 seg->bv_offset = bvec->bv_offset % PAGE_SIZE; 179 seg->bv_len = bvec->bv_len; 180 } else { 181 seg->bv_offset = 0; 182 seg->bv_len = total - last_page * PAGE_SIZE; 183 } 184 } 185 186 #endif /* __LINUX_BVEC_ITER_H */ 187