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 union { 22 __u32 page_offset; 23 unsigned int bv_offset; 24 }; 25 }; 26 27 struct bvec_iter { 28 sector_t bi_sector; /* device address in 512 byte 29 sectors */ 30 unsigned int bi_size; /* residual I/O count */ 31 32 unsigned int bi_idx; /* current index into bvl_vec */ 33 34 unsigned int bi_bvec_done; /* number of bytes completed in 35 current bvec */ 36 }; 37 38 struct bvec_iter_all { 39 struct bio_vec bv; 40 int idx; 41 unsigned done; 42 }; 43 44 /* 45 * various member access, note that bio_data should of course not be used 46 * on highmem page vectors 47 */ 48 #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) 49 50 /* multi-page (mp_bvec) helpers */ 51 #define mp_bvec_iter_page(bvec, iter) \ 52 (__bvec_iter_bvec((bvec), (iter))->bv_page) 53 54 #define mp_bvec_iter_len(bvec, iter) \ 55 min((iter).bi_size, \ 56 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done) 57 58 #define mp_bvec_iter_offset(bvec, iter) \ 59 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) 60 61 #define mp_bvec_iter_page_idx(bvec, iter) \ 62 (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE) 63 64 #define mp_bvec_iter_bvec(bvec, iter) \ 65 ((struct bio_vec) { \ 66 .bv_page = mp_bvec_iter_page((bvec), (iter)), \ 67 .bv_len = mp_bvec_iter_len((bvec), (iter)), \ 68 .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \ 69 }) 70 71 /* For building single-page bvec in flight */ 72 #define bvec_iter_offset(bvec, iter) \ 73 (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE) 74 75 #define bvec_iter_len(bvec, iter) \ 76 min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \ 77 PAGE_SIZE - bvec_iter_offset((bvec), (iter))) 78 79 #define bvec_iter_page(bvec, iter) \ 80 (mp_bvec_iter_page((bvec), (iter)) + \ 81 mp_bvec_iter_page_idx((bvec), (iter))) 82 83 #define bvec_iter_bvec(bvec, iter) \ 84 ((struct bio_vec) { \ 85 .bv_page = bvec_iter_page((bvec), (iter)), \ 86 .bv_len = bvec_iter_len((bvec), (iter)), \ 87 .bv_offset = bvec_iter_offset((bvec), (iter)), \ 88 }) 89 90 static inline bool bvec_iter_advance(const struct bio_vec *bv, 91 struct bvec_iter *iter, unsigned bytes) 92 { 93 if (WARN_ONCE(bytes > iter->bi_size, 94 "Attempted to advance past end of bvec iter\n")) { 95 iter->bi_size = 0; 96 return false; 97 } 98 99 while (bytes) { 100 const struct bio_vec *cur = bv + iter->bi_idx; 101 unsigned len = min3(bytes, iter->bi_size, 102 cur->bv_len - iter->bi_bvec_done); 103 104 bytes -= len; 105 iter->bi_size -= len; 106 iter->bi_bvec_done += len; 107 108 if (iter->bi_bvec_done == cur->bv_len) { 109 iter->bi_bvec_done = 0; 110 iter->bi_idx++; 111 } 112 } 113 return true; 114 } 115 116 #define for_each_bvec(bvl, bio_vec, iter, start) \ 117 for (iter = (start); \ 118 (iter).bi_size && \ 119 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \ 120 bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len)) 121 122 /* for iterating one bio from start to end */ 123 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \ 124 { \ 125 .bi_sector = 0, \ 126 .bi_size = UINT_MAX, \ 127 .bi_idx = 0, \ 128 .bi_bvec_done = 0, \ 129 } 130 131 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all) 132 { 133 iter_all->done = 0; 134 iter_all->idx = 0; 135 136 return &iter_all->bv; 137 } 138 139 static inline void bvec_advance(const struct bio_vec *bvec, 140 struct bvec_iter_all *iter_all) 141 { 142 struct bio_vec *bv = &iter_all->bv; 143 144 if (iter_all->done) { 145 bv->bv_page++; 146 bv->bv_offset = 0; 147 } else { 148 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT); 149 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK; 150 } 151 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset, 152 bvec->bv_len - iter_all->done); 153 iter_all->done += bv->bv_len; 154 155 if (iter_all->done == bvec->bv_len) { 156 iter_all->idx++; 157 iter_all->done = 0; 158 } 159 } 160 161 /* 162 * Get the last single-page segment from the multi-page bvec and store it 163 * in @seg 164 */ 165 static inline void mp_bvec_last_segment(const struct bio_vec *bvec, 166 struct bio_vec *seg) 167 { 168 unsigned total = bvec->bv_offset + bvec->bv_len; 169 unsigned last_page = (total - 1) / PAGE_SIZE; 170 171 seg->bv_page = bvec->bv_page + last_page; 172 173 /* the whole segment is inside the last page */ 174 if (bvec->bv_offset >= last_page * PAGE_SIZE) { 175 seg->bv_offset = bvec->bv_offset % PAGE_SIZE; 176 seg->bv_len = bvec->bv_len; 177 } else { 178 seg->bv_offset = 0; 179 seg->bv_len = total - last_page * PAGE_SIZE; 180 } 181 } 182 183 #endif /* __LINUX_BVEC_ITER_H */ 184