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 27 /* 28 * was unsigned short, but we might as well be ready for > 64kB I/O pages 29 */ 30 struct bio_vec { 31 struct page *bv_page; 32 unsigned int bv_len; 33 unsigned int bv_offset; 34 }; 35 36 struct bvec_iter { 37 sector_t bi_sector; /* device address in 512 byte 38 sectors */ 39 unsigned int bi_size; /* residual I/O count */ 40 41 unsigned int bi_idx; /* current index into bvl_vec */ 42 43 unsigned int bi_bvec_done; /* number of bytes completed in 44 current bvec */ 45 }; 46 47 /* 48 * various member access, note that bio_data should of course not be used 49 * on highmem page vectors 50 */ 51 #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) 52 53 #define bvec_iter_page(bvec, iter) \ 54 (__bvec_iter_bvec((bvec), (iter))->bv_page) 55 56 #define bvec_iter_len(bvec, iter) \ 57 min((iter).bi_size, \ 58 __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done) 59 60 #define bvec_iter_offset(bvec, iter) \ 61 (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) 62 63 #define bvec_iter_bvec(bvec, iter) \ 64 ((struct bio_vec) { \ 65 .bv_page = bvec_iter_page((bvec), (iter)), \ 66 .bv_len = bvec_iter_len((bvec), (iter)), \ 67 .bv_offset = bvec_iter_offset((bvec), (iter)), \ 68 }) 69 70 static inline bool bvec_iter_advance(const struct bio_vec *bv, 71 struct bvec_iter *iter, unsigned bytes) 72 { 73 if (WARN_ONCE(bytes > iter->bi_size, 74 "Attempted to advance past end of bvec iter\n")) { 75 iter->bi_size = 0; 76 return false; 77 } 78 79 while (bytes) { 80 unsigned iter_len = bvec_iter_len(bv, *iter); 81 unsigned len = min(bytes, iter_len); 82 83 bytes -= len; 84 iter->bi_size -= len; 85 iter->bi_bvec_done += len; 86 87 if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) { 88 iter->bi_bvec_done = 0; 89 iter->bi_idx++; 90 } 91 } 92 return true; 93 } 94 95 static inline bool bvec_iter_rewind(const struct bio_vec *bv, 96 struct bvec_iter *iter, 97 unsigned int bytes) 98 { 99 while (bytes) { 100 unsigned len = min(bytes, iter->bi_bvec_done); 101 102 if (iter->bi_bvec_done == 0) { 103 if (WARN_ONCE(iter->bi_idx == 0, 104 "Attempted to rewind iter beyond " 105 "bvec's boundaries\n")) { 106 return false; 107 } 108 iter->bi_idx--; 109 iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len; 110 continue; 111 } 112 bytes -= len; 113 iter->bi_size += len; 114 iter->bi_bvec_done -= len; 115 } 116 return true; 117 } 118 119 #define for_each_bvec(bvl, bio_vec, iter, start) \ 120 for (iter = (start); \ 121 (iter).bi_size && \ 122 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \ 123 bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len)) 124 125 /* for iterating one bio from start to end */ 126 #define BVEC_ITER_ALL_INIT (struct bvec_iter) \ 127 { \ 128 .bi_sector = 0, \ 129 .bi_size = UINT_MAX, \ 130 .bi_idx = 0, \ 131 .bi_bvec_done = 0, \ 132 } 133 134 #endif /* __LINUX_BVEC_ITER_H */ 135