patches/kernel/0009-block-add-a-lower-level-bio_add_page-interface.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Christoph Hellwig <hch@lst.de>
   3 Date: Tue, 9 Oct 2018 17:04:39 +0100
   4 Subject: [PATCH] block: add a lower-level bio_add_page interface
   5
   6 Buglink: https://bugs.launchpad.net/bugs/1796542
   7
   8 For the upcoming removal of buffer heads in XFS we need to keep track of
   9 the number of outstanding writeback requests per page.  For this we need
  10 to know if bio_add_page merged a region with the previous bvec or not.
  11 Instead of adding additional arguments this refactors bio_add_page to
  12 be implemented using three lower level helpers which users like XFS can
  13 use directly if they care about the merge decisions.
  14
  15 Signed-off-by: Christoph Hellwig <hch@lst.de>
  16 Reviewed-by: Jens Axboe <axboe@kernel.dk>
  17 Reviewed-by: Ming Lei <ming.lei@redhat.com>
  18 Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
  19 Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
  20 (cherry picked from commit 0aa69fd32a5f766e997ca8ab4723c5a1146efa8b)
  21 Signed-off-by: Colin Ian King <colin.king@canonical.com>
  22 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  23 ---
  24  block/bio.c         | 98 ++++++++++++++++++++++++++++++++++-------------------
  25  include/linux/bio.h |  9 +++++
  26  2 files changed, 73 insertions(+), 34 deletions(-)
  27
  28 diff --git a/block/bio.c b/block/bio.c
  29 index 4b48f8eefc4c..2636d15af979 100644
  30 --- a/block/bio.c
  31 +++ b/block/bio.c
  32 @@ -773,7 +773,7 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
  33                         return 0;
  34         }
  35
  36 -       if (bio->bi_vcnt >= bio->bi_max_vecs)
  37 +       if (bio_full(bio))
  38                 return 0;
  39
  40         /*
  41 @@ -821,6 +821,65 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
  42  EXPORT_SYMBOL(bio_add_pc_page);
  43
  44  /**
  45 + * __bio_try_merge_page - try appending data to an existing bvec.
  46 + * @bio: destination bio
  47 + * @page: page to add
  48 + * @len: length of the data to add
  49 + * @off: offset of the data in @page
  50 + *
  51 + * Try to add the data at @page + @off to the last bvec of @bio.  This is a
  52 + * a useful optimisation for file systems with a block size smaller than the
  53 + * page size.
  54 + *
  55 + * Return %true on success or %false on failure.
  56 + */
  57 +bool __bio_try_merge_page(struct bio *bio, struct page *page,
  58 +               unsigned int len, unsigned int off)
  59 +{
  60 +       if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
  61 +               return false;
  62 +
  63 +       if (bio->bi_vcnt > 0) {
  64 +               struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
  65 +
  66 +               if (page == bv->bv_page && off == bv->bv_offset + bv->bv_len) {
  67 +                       bv->bv_len += len;
  68 +                       bio->bi_iter.bi_size += len;
  69 +                       return true;
  70 +               }
  71 +       }
  72 +       return false;
  73 +}
  74 +EXPORT_SYMBOL_GPL(__bio_try_merge_page);
  75 +
  76 +/**
  77 + * __bio_add_page - add page to a bio in a new segment
  78 + * @bio: destination bio
  79 + * @page: page to add
  80 + * @len: length of the data to add
  81 + * @off: offset of the data in @page
  82 + *
  83 + * Add the data at @page + @off to @bio as a new bvec.  The caller must ensure
  84 + * that @bio has space for another bvec.
  85 + */
  86 +void __bio_add_page(struct bio *bio, struct page *page,
  87 +               unsigned int len, unsigned int off)
  88 +{
  89 +       struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt];
  90 +
  91 +       WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED));
  92 +       WARN_ON_ONCE(bio_full(bio));
  93 +
  94 +       bv->bv_page = page;
  95 +       bv->bv_offset = off;
  96 +       bv->bv_len = len;
  97 +
  98 +       bio->bi_iter.bi_size += len;
  99 +       bio->bi_vcnt++;
 100 +}
 101 +EXPORT_SYMBOL_GPL(__bio_add_page);
 102 +
 103 +/**
 104   *     bio_add_page    -       attempt to add page to bio
 105   *     @bio: destination bio
 106   *     @page: page to add
 107 @@ -833,40 +892,11 @@ EXPORT_SYMBOL(bio_add_pc_page);
 108  int bio_add_page(struct bio *bio, struct page *page,
 109                  unsigned int len, unsigned int offset)
 110  {
 111 -       struct bio_vec *bv;
 112 -
 113 -       /*
 114 -        * cloned bio must not modify vec list
 115 -        */
 116 -       if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
 117 -               return 0;
 118 -
 119 -       /*
 120 -        * For filesystems with a blocksize smaller than the pagesize
 121 -        * we will often be called with the same page as last time and
 122 -        * a consecutive offset.  Optimize this special case.
 123 -        */
 124 -       if (bio->bi_vcnt > 0) {
 125 -               bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
 126 -
 127 -               if (page == bv->bv_page &&
 128 -                   offset == bv->bv_offset + bv->bv_len) {
 129 -                       bv->bv_len += len;
 130 -                       goto done;
 131 -               }
 132 +       if (!__bio_try_merge_page(bio, page, len, offset)) {
 133 +               if (bio_full(bio))
 134 +                       return 0;
 135 +               __bio_add_page(bio, page, len, offset);
 136         }
 137 -
 138 -       if (bio->bi_vcnt >= bio->bi_max_vecs)
 139 -               return 0;
 140 -
 141 -       bv              = &bio->bi_io_vec[bio->bi_vcnt];
 142 -       bv->bv_page     = page;
 143 -       bv->bv_len      = len;
 144 -       bv->bv_offset   = offset;
 145 -
 146 -       bio->bi_vcnt++;
 147 -done:
 148 -       bio->bi_iter.bi_size += len;
 149         return len;
 150  }
 151  EXPORT_SYMBOL(bio_add_page);
 152 diff --git a/include/linux/bio.h b/include/linux/bio.h
 153 index a98c6ac575cf..3440870712d4 100644
 154 --- a/include/linux/bio.h
 155 +++ b/include/linux/bio.h
 156 @@ -123,6 +123,11 @@ static inline void *bio_data(struct bio *bio)
 157         return NULL;
 158  }
 159
 160 +static inline bool bio_full(struct bio *bio)
 161 +{
 162 +       return bio->bi_vcnt >= bio->bi_max_vecs;
 163 +}
 164 +
 165  /*
 166   * will die
 167   */
 168 @@ -447,6 +452,10 @@ void bio_chain(struct bio *, struct bio *);
 169  extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
 170  extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
 171                            unsigned int, unsigned int);
 172 +bool __bio_try_merge_page(struct bio *bio, struct page *page,
 173 +               unsigned int len, unsigned int off);
 174 +void __bio_add_page(struct bio *bio, struct page *page,
 175 +               unsigned int len, unsigned int off);
 176  int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
 177  struct rq_map_data;
 178  extern struct bio *bio_map_user_iov(struct request_queue *,