LCOV - code coverage report
Current view: top level - include/linux - bvec.h (source / functions) Hit Total Coverage
Test: landlock.info Lines: 36 38 94.7 %
Date: 2021-04-22 12:43:58 Functions: 3 3 100.0 %

          Line data    Source code
       1             : /* SPDX-License-Identifier: GPL-2.0 */
       2             : /*
       3             :  * bvec iterator
       4             :  *
       5             :  * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
       6             :  */
       7             : #ifndef __LINUX_BVEC_ITER_H
       8             : #define __LINUX_BVEC_ITER_H
       9             : 
      10             : #include <linux/bug.h>
      11             : #include <linux/errno.h>
      12             : #include <linux/limits.h>
      13             : #include <linux/minmax.h>
      14             : #include <linux/mm.h>
      15             : #include <linux/types.h>
      16             : 
      17             : struct page;
      18             : 
      19             : /**
      20             :  * struct bio_vec - a contiguous range of physical memory addresses
      21             :  * @bv_page:   First page associated with the address range.
      22             :  * @bv_len:    Number of bytes in the address range.
      23             :  * @bv_offset: Start of the address range relative to the start of @bv_page.
      24             :  *
      25             :  * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
      26             :  *
      27             :  *   nth_page(@bv_page, n) == @bv_page + n
      28             :  *
      29             :  * This holds because page_is_mergeable() checks the above property.
      30             :  */
      31             : struct bio_vec {
      32             :         struct page     *bv_page;
      33             :         unsigned int    bv_len;
      34             :         unsigned int    bv_offset;
      35             : };
      36             : 
      37             : struct bvec_iter {
      38             :         sector_t                bi_sector;      /* device address in 512 byte
      39             :                                                    sectors */
      40             :         unsigned int            bi_size;        /* residual I/O count */
      41             : 
      42             :         unsigned int            bi_idx;         /* current index into bvl_vec */
      43             : 
      44             :         unsigned int            bi_bvec_done;   /* number of bytes completed in
      45             :                                                    current bvec */
      46             : };
      47             : 
      48             : struct bvec_iter_all {
      49             :         struct bio_vec  bv;
      50             :         int             idx;
      51             :         unsigned        done;
      52             : };
      53             : 
      54             : /*
      55             :  * various member access, note that bio_data should of course not be used
      56             :  * on highmem page vectors
      57             :  */
      58             : #define __bvec_iter_bvec(bvec, iter)    (&(bvec)[(iter).bi_idx])
      59             : 
      60             : /* multi-page (mp_bvec) helpers */
      61             : #define mp_bvec_iter_page(bvec, iter)                           \
      62             :         (__bvec_iter_bvec((bvec), (iter))->bv_page)
      63             : 
      64             : #define mp_bvec_iter_len(bvec, iter)                            \
      65             :         min((iter).bi_size,                                     \
      66             :             __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
      67             : 
      68             : #define mp_bvec_iter_offset(bvec, iter)                         \
      69             :         (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
      70             : 
      71             : #define mp_bvec_iter_page_idx(bvec, iter)                       \
      72             :         (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
      73             : 
      74             : #define mp_bvec_iter_bvec(bvec, iter)                           \
      75             : ((struct bio_vec) {                                             \
      76             :         .bv_page        = mp_bvec_iter_page((bvec), (iter)),    \
      77             :         .bv_len         = mp_bvec_iter_len((bvec), (iter)),     \
      78             :         .bv_offset      = mp_bvec_iter_offset((bvec), (iter)),  \
      79             : })
      80             : 
      81             : /* For building single-page bvec in flight */
      82             :  #define bvec_iter_offset(bvec, iter)                           \
      83             :         (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
      84             : 
      85             : #define bvec_iter_len(bvec, iter)                               \
      86             :         min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),               \
      87             :               PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
      88             : 
      89             : #define bvec_iter_page(bvec, iter)                              \
      90             :         (mp_bvec_iter_page((bvec), (iter)) +                    \
      91             :          mp_bvec_iter_page_idx((bvec), (iter)))
      92             : 
      93             : #define bvec_iter_bvec(bvec, iter)                              \
      94             : ((struct bio_vec) {                                             \
      95             :         .bv_page        = bvec_iter_page((bvec), (iter)),       \
      96             :         .bv_len         = bvec_iter_len((bvec), (iter)),        \
      97             :         .bv_offset      = bvec_iter_offset((bvec), (iter)),     \
      98             : })
      99             : 
     100        9374 : static inline bool bvec_iter_advance(const struct bio_vec *bv,
     101             :                 struct bvec_iter *iter, unsigned bytes)
     102             : {
     103        9374 :         unsigned int idx = iter->bi_idx;
     104             : 
     105        9374 :         if (WARN_ONCE(bytes > iter->bi_size,
     106             :                      "Attempted to advance past end of bvec iter\n")) {
     107           0 :                 iter->bi_size = 0;
     108           0 :                 return false;
     109             :         }
     110             : 
     111        9374 :         iter->bi_size -= bytes;
     112        9374 :         bytes += iter->bi_bvec_done;
     113             : 
     114       22540 :         while (bytes && bytes >= bv[idx].bv_len) {
     115       13166 :                 bytes -= bv[idx].bv_len;
     116       13166 :                 idx++;
     117             :         }
     118             : 
     119        9374 :         iter->bi_idx = idx;
     120        9374 :         iter->bi_bvec_done = bytes;
     121        9374 :         return true;
     122             : }
     123             : 
     124             : /*
     125             :  * A simpler version of bvec_iter_advance(), @bytes should not span
     126             :  * across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len
     127             :  */
     128       18483 : static inline void bvec_iter_advance_single(const struct bio_vec *bv,
     129             :                                 struct bvec_iter *iter, unsigned int bytes)
     130             : {
     131       18483 :         unsigned int done = iter->bi_bvec_done + bytes;
     132             : 
     133       18483 :         if (done == bv[iter->bi_idx].bv_len) {
     134       18483 :                 done = 0;
     135       18483 :                 iter->bi_idx++;
     136             :         }
     137       18483 :         iter->bi_bvec_done = done;
     138       18483 :         iter->bi_size -= bytes;
     139       18483 : }
     140             : 
     141             : #define for_each_bvec(bvl, bio_vec, iter, start)                        \
     142             :         for (iter = (start);                                            \
     143             :              (iter).bi_size &&                                          \
     144             :                 ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
     145             :              bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len))
     146             : 
     147             : /* for iterating one bio from start to end */
     148             : #define BVEC_ITER_ALL_INIT (struct bvec_iter)                           \
     149             : {                                                                       \
     150             :         .bi_sector      = 0,                                            \
     151             :         .bi_size        = UINT_MAX,                                     \
     152             :         .bi_idx         = 0,                                            \
     153             :         .bi_bvec_done   = 0,                                            \
     154             : }
     155             : 
     156        1869 : static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
     157             : {
     158        1869 :         iter_all->done = 0;
     159        1869 :         iter_all->idx = 0;
     160             : 
     161        1869 :         return &iter_all->bv;
     162             : }
     163             : 
     164       22054 : static inline void bvec_advance(const struct bio_vec *bvec,
     165             :                                 struct bvec_iter_all *iter_all)
     166             : {
     167       22054 :         struct bio_vec *bv = &iter_all->bv;
     168             : 
     169       22054 :         if (iter_all->done) {
     170       16263 :                 bv->bv_page++;
     171       16263 :                 bv->bv_offset = 0;
     172             :         } else {
     173        5791 :                 bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
     174        5791 :                 bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
     175             :         }
     176       22054 :         bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
     177             :                            bvec->bv_len - iter_all->done);
     178       22054 :         iter_all->done += bv->bv_len;
     179             : 
     180       22054 :         if (iter_all->done == bvec->bv_len) {
     181        5791 :                 iter_all->idx++;
     182        5791 :                 iter_all->done = 0;
     183             :         }
     184       22054 : }
     185             : 
     186             : #endif /* __LINUX_BVEC_ITER_H */

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