| /* SPDX-License-Identifier: GPL-2.0 */ |
| /* |
| * bvec iterator |
| * |
| * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com> |
| */ |
| #ifndef __LINUX_BVEC_ITER_H |
| #define __LINUX_BVEC_ITER_H |
| |
| #include <linux/bug.h> |
| #include <linux/errno.h> |
| #include <linux/limits.h> |
| #include <linux/minmax.h> |
| #include <linux/mm.h> |
| #include <linux/types.h> |
| |
| struct page; |
| |
| /** |
| * struct bio_vec - a contiguous range of physical memory addresses |
| * @bv_page: First page associated with the address range. |
| * @bv_len: Number of bytes in the address range. |
| * @bv_offset: Start of the address range relative to the start of @bv_page. |
| * |
| * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len: |
| * |
| * nth_page(@bv_page, n) == @bv_page + n |
| * |
| * This holds because page_is_mergeable() checks the above property. |
| */ |
| struct bio_vec { |
| struct page *bv_page; |
| unsigned int bv_len; |
| unsigned int bv_offset; |
| }; |
| |
| struct bvec_iter { |
| sector_t bi_sector; /* device address in 512 byte |
| sectors */ |
| unsigned int bi_size; /* residual I/O count */ |
| |
| unsigned int bi_idx; /* current index into bvl_vec */ |
| |
| unsigned int bi_bvec_done; /* number of bytes completed in |
| current bvec */ |
| }; |
| |
| struct bvec_iter_all { |
| struct bio_vec bv; |
| int idx; |
| unsigned done; |
| }; |
| |
| /* |
| * various member access, note that bio_data should of course not be used |
| * on highmem page vectors |
| */ |
| #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) |
| |
| /* multi-page (mp_bvec) helpers */ |
| #define mp_bvec_iter_page(bvec, iter) \ |
| (__bvec_iter_bvec((bvec), (iter))->bv_page) |
| |
| #define mp_bvec_iter_len(bvec, iter) \ |
| min((iter).bi_size, \ |
| __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done) |
| |
| #define mp_bvec_iter_offset(bvec, iter) \ |
| (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) |
| |
| #define mp_bvec_iter_page_idx(bvec, iter) \ |
| (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE) |
| |
| #define mp_bvec_iter_bvec(bvec, iter) \ |
| ((struct bio_vec) { \ |
| .bv_page = mp_bvec_iter_page((bvec), (iter)), \ |
| .bv_len = mp_bvec_iter_len((bvec), (iter)), \ |
| .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \ |
| }) |
| |
| /* For building single-page bvec in flight */ |
| #define bvec_iter_offset(bvec, iter) \ |
| (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE) |
| |
| #define bvec_iter_len(bvec, iter) \ |
| min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \ |
| PAGE_SIZE - bvec_iter_offset((bvec), (iter))) |
| |
| #define bvec_iter_page(bvec, iter) \ |
| (mp_bvec_iter_page((bvec), (iter)) + \ |
| mp_bvec_iter_page_idx((bvec), (iter))) |
| |
| #define bvec_iter_bvec(bvec, iter) \ |
| ((struct bio_vec) { \ |
| .bv_page = bvec_iter_page((bvec), (iter)), \ |
| .bv_len = bvec_iter_len((bvec), (iter)), \ |
| .bv_offset = bvec_iter_offset((bvec), (iter)), \ |
| }) |
| |
| static inline bool bvec_iter_advance(const struct bio_vec *bv, |
| struct bvec_iter *iter, unsigned bytes) |
| { |
| unsigned int idx = iter->bi_idx; |
| |
| if (WARN_ONCE(bytes > iter->bi_size, |
| "Attempted to advance past end of bvec iter\n")) { |
| iter->bi_size = 0; |
| return false; |
| } |
| |
| iter->bi_size -= bytes; |
| bytes += iter->bi_bvec_done; |
| |
| while (bytes && bytes >= bv[idx].bv_len) { |
| bytes -= bv[idx].bv_len; |
| idx++; |
| } |
| |
| iter->bi_idx = idx; |
| iter->bi_bvec_done = bytes; |
| return true; |
| } |
| |
| /* |
| * A simpler version of bvec_iter_advance(), @bytes should not span |
| * across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len |
| */ |
| static inline void bvec_iter_advance_single(const struct bio_vec *bv, |
| struct bvec_iter *iter, unsigned int bytes) |
| { |
| unsigned int done = iter->bi_bvec_done + bytes; |
| |
| if (done == bv[iter->bi_idx].bv_len) { |
| done = 0; |
| iter->bi_idx++; |
| } |
| iter->bi_bvec_done = done; |
| iter->bi_size -= bytes; |
| } |
| |
| #define for_each_bvec(bvl, bio_vec, iter, start) \ |
| for (iter = (start); \ |
| (iter).bi_size && \ |
| ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \ |
| bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len)) |
| |
| /* for iterating one bio from start to end */ |
| #define BVEC_ITER_ALL_INIT (struct bvec_iter) \ |
| { \ |
| .bi_sector = 0, \ |
| .bi_size = UINT_MAX, \ |
| .bi_idx = 0, \ |
| .bi_bvec_done = 0, \ |
| } |
| |
| static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all) |
| { |
| iter_all->done = 0; |
| iter_all->idx = 0; |
| |
| return &iter_all->bv; |
| } |
| |
| static inline void bvec_advance(const struct bio_vec *bvec, |
| struct bvec_iter_all *iter_all) |
| { |
| struct bio_vec *bv = &iter_all->bv; |
| |
| if (iter_all->done) { |
| bv->bv_page++; |
| bv->bv_offset = 0; |
| } else { |
| bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT); |
| bv->bv_offset = bvec->bv_offset & ~PAGE_MASK; |
| } |
| bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset, |
| bvec->bv_len - iter_all->done); |
| iter_all->done += bv->bv_len; |
| |
| if (iter_all->done == bvec->bv_len) { |
| iter_all->idx++; |
| iter_all->done = 0; |
| } |
| } |
| |
| #endif /* __LINUX_BVEC_ITER_H */ |