inline-ext4_get_block-into-readpage

   1 ext4: call ext4_map_blocks() directly from read_page.c
   2
   3 Use ext4_map_blocks() directly instead of going through
   4 ext4_get_block().  This allows us to drop out a lot of generic code
   5 that was not needed for ext4.
   6
   7 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   8
   9
  10 ---
  11  fs/ext4/readpage.c | 83 ++++++++++++++++++-----------------------------------------------------------------
  12  1 file changed, 18 insertions(+), 65 deletions(-)
  13
  14 diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
  15 index 3b29da1..ce3ecc1 100644
  16 --- a/fs/ext4/readpage.c
  17 +++ b/fs/ext4/readpage.c
  18 @@ -85,49 +85,6 @@ mpage_alloc(struct block_device *bdev,
  19  }
  20
  21  /*
  22 - * support function for mpage_readpages.  The fs supplied get_block might
  23 - * return an up to date buffer.  This is used to map that buffer into
  24 - * the page, which allows readpage to avoid triggering a duplicate call
  25 - * to get_block.
  26 - *
  27 - * The idea is to avoid adding buffers to pages that don't already have
  28 - * them.  So when the buffer is up to date and the page size == block size,
  29 - * this marks the page up to date instead of adding new buffers.
  30 - */
  31 -static void
  32 -map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
  33 -{
  34 -       struct inode *inode = page->mapping->host;
  35 -       struct buffer_head *page_bh, *head;
  36 -       int block = 0;
  37 -
  38 -       if (!page_has_buffers(page)) {
  39 -               /*
  40 -                * don't make any buffers if there is only one buffer on
  41 -                * the page and the page just needs to be set up to date
  42 -                */
  43 -               if (inode->i_blkbits == PAGE_CACHE_SHIFT &&
  44 -                   buffer_uptodate(bh)) {
  45 -                       SetPageUptodate(page);
  46 -                       return;
  47 -               }
  48 -               create_empty_buffers(page, 1 << inode->i_blkbits, 0);
  49 -       }
  50 -       head = page_buffers(page);
  51 -       page_bh = head;
  52 -       do {
  53 -               if (block == page_block) {
  54 -                       page_bh->b_state = bh->b_state;
  55 -                       page_bh->b_bdev = bh->b_bdev;
  56 -                       page_bh->b_blocknr = bh->b_blocknr;
  57 -                       break;
  58 -               }
  59 -               page_bh = page_bh->b_this_page;
  60 -               block++;
  61 -       } while (page_bh != head);
  62 -}
  63 -
  64 -/*
  65   * This is the worker routine which does all the work of mapping the disk
  66   * blocks and constructs largest possible bios, submits them for IO if the
  67   * blocks are not contiguous on the disk.
  68 @@ -138,8 +95,8 @@ map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
  69   */
  70  static struct bio *
  71  do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
  72 -               sector_t *last_block_in_bio, struct buffer_head *map_bh,
  73 -               unsigned long *first_logical_block, get_block_t get_block)
  74 +                 sector_t *last_block_in_bio, struct buffer_head *map_bh,
  75 +                 unsigned long *first_logical_block)
  76  {
  77         struct inode *inode = page->mapping->host;
  78         const unsigned blkbits = inode->i_blkbits;
  79 @@ -151,7 +108,7 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
  80         sector_t blocks[MAX_BUF_PER_PAGE];
  81         unsigned page_block;
  82         unsigned first_hole = blocks_per_page;
  83 -       struct block_device *bdev = NULL;
  84 +       struct block_device *bdev = inode->i_sb->s_bdev;
  85         int length;
  86         int fully_mapped = 1;
  87         unsigned nblocks;
  88 @@ -188,7 +145,6 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
  89                         page_block++;
  90                         block_in_file++;
  91                 }
  92 -               bdev = map_bh->b_bdev;
  93         }
  94
  95         /*
  96 @@ -200,9 +156,19 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
  97                 map_bh->b_size = 0;
  98
  99                 if (block_in_file < last_block) {
 100 -                       map_bh->b_size = (last_block-block_in_file) << blkbits;
 101 -                       if (get_block(inode, block_in_file, map_bh, 0))
 102 +                       struct ext4_map_blocks map;
 103 +                       int ret;
 104 +
 105 +                       map.m_lblk = block_in_file;
 106 +                       map.m_len = last_block - block_in_file;
 107 +                       ret = ext4_map_blocks(NULL, inode, &map, 0);
 108 +                       if (ret < 0)
 109                                 goto confused;
 110 +                       map_bh->b_blocknr = map.m_pblk;
 111 +                       map_bh->b_bdev = bdev;
 112 +                       map_bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 113 +                       map_bh->b_state = map.m_flags;
 114 +
 115                         *first_logical_block = block_in_file;
 116                 }
 117
 118 @@ -215,17 +181,6 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
 119                         continue;
 120                 }
 121
 122 -               /* some filesystems will copy data into the page during
 123 -                * the get_block call, in which case we don't want to
 124 -                * read it again.  map_buffer_to_page copies the data
 125 -                * we just collected from get_block into the page's buffers
 126 -                * so readpage doesn't have to repeat the get_block call
 127 -                */
 128 -               if (buffer_uptodate(map_bh)) {
 129 -                       map_buffer_to_page(page, map_bh, page_block);
 130 -                       goto confused;
 131 -               }
 132 -
 133                 if (first_hole != blocks_per_page)
 134                         goto confused;          /* hole -> non-hole */
 135
 136 @@ -243,7 +198,6 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
 137                         page_block++;
 138                         block_in_file++;
 139                 }
 140 -               bdev = map_bh->b_bdev;
 141         }
 142
 143         if (first_hole != blocks_per_page) {
 144 @@ -303,7 +257,7 @@ confused:
 145         if (bio)
 146                 bio = mpage_bio_submit(READ, bio);
 147         if (!PageUptodate(page))
 148 -               block_read_full_page(page, get_block);
 149 +               block_read_full_page(page, ext4_get_block);
 150         else
 151                 unlock_page(page);
 152         goto out;
 153 @@ -329,7 +283,7 @@ int ext4_readpage(struct file *file, struct page *page)
 154         map_bh.b_state = 0;
 155         map_bh.b_size = 0;
 156         bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
 157 -                       &map_bh, &first_logical_block, ext4_get_block);
 158 +                       &map_bh, &first_logical_block);
 159         if (bio)
 160                 mpage_bio_submit(READ, bio);
 161         return 0;
 162 @@ -361,8 +315,7 @@ int ext4_readpages(struct file *file, struct address_space *mapping,
 163                         bio = do_mpage_readpage(bio, page,
 164                                         nr_pages - page_idx,
 165                                         &last_block_in_bio, &map_bh,
 166 -                                       &first_logical_block,
 167 -                                       ext4_get_block);
 168 +                                       &first_logical_block);
 169                 }
 170                 page_cache_release(page);
 171         }