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 * struct bio_vec - a contiguous range of physical memory addresses 17 * @bv_page: First page associated with the address range. 18 * @bv_len: Number of bytes in the address range. 19 * @bv_offset: Start of the address range relative to the start of @bv_page. 20 * 21 * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len: 22 * 23 * nth_page(@bv_page, n) == @bv_page + n 24 * 25 * This holds because page_is_mergeable() checks the above property. 26 */ 27 struct bio_vec { 28 struct page *bv_page; 29 unsigned int bv_len; 30 unsigned int bv_offset; 31 }; 32 33 struct bvec_iter { 34 sector_t bi_sector; /* device address in 512 byte 35 sectors */ 36 unsigned int bi_size; /* residual I/O count */ 37 38 unsigned int bi_idx; /* current index into bvl_vec */ 39 40 unsigned int bi_bvec_done; /* number of bytes completed in 41 current bvec */ 42 }; 43 44 struct bvec_iter_all { 45 struct bio_vec bv; 46 int idx; 47 unsigned done; 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 (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 unsigned int idx = iter->bi_idx; 100 101 if (WARN_ONCE(bytes > iter->bi_size, 102 "Attempted to advance past end of bvec iter\n")) { 103 iter->bi_size = 0; 104 return false; 105 } 106 107 iter->bi_size -= bytes; 108 bytes += iter->bi_bvec_done; 109 110 while (bytes && bytes >= bv[idx].bv_len) { 111 bytes -= bv[idx].bv_len; 112 idx++; 113 } 114 115 iter->bi_idx = idx; 116 iter->bi_bvec_done = bytes; 117 return true; 118 } 119 120 static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter) 121 { 122 iter->bi_bvec_done = 0; 123 iter->bi_idx++; 124 } 125 126 #define for_each_bvec(bvl, bio_vec, iter, start) \ 127 for (iter = (start); \ 128 (iter).bi_size && \ 129 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \ 130 (bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \ 131 (bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter))) 132 133 /* for iterating one bio from start to end */ 134 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \ 135 { \ 136 .bi_sector = 0, \ 137 .bi_size = UINT_MAX, \ 138 .bi_idx = 0, \ 139 .bi_bvec_done = 0, \ 140 } 141 142 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all) 143 { 144 iter_all->done = 0; 145 iter_all->idx = 0; 146 147 return &iter_all->bv; 148 } 149 150 static inline void bvec_advance(const struct bio_vec *bvec, 151 struct bvec_iter_all *iter_all) 152 { 153 struct bio_vec *bv = &iter_all->bv; 154 155 if (iter_all->done) { 156 bv->bv_page++; 157 bv->bv_offset = 0; 158 } else { 159 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT); 160 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK; 161 } 162 bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset, 163 bvec->bv_len - iter_all->done); 164 iter_all->done += bv->bv_len; 165 166 if (iter_all->done == bvec->bv_len) { 167 iter_all->idx++; 168 iter_all->done = 0; 169 } 170 } 171 172 #endif /* __LINUX_BVEC_ITER_H */ 173