delalloc-block-reservation-estimate-blocks-to-reserve.patch

   1 ext4: delalloc --estimate need metadata blocks to reserve
   2
   3 From: Mingming cao <cmm@us.ibm.com>
   4
   5 Calculate the number of metadata blocks needed to allocate blocks
   6 Worse case is one block per extent
   7
   8 Signed-off-by: Mingming cao <cmm@us.ibm.com>
   9
  10 ---
  11  fs/ext4/ext4_extents.h |    1 +
  12  fs/ext4/extents.c      |   30 ++++++++++++++++++++++++++++++
  13  2 files changed, 31 insertions(+)
  14
  15 Index: linux-2.6.26-rc5/fs/ext4/ext4_extents.h
  16 ===================================================================
  17 --- linux-2.6.26-rc5.orig/fs/ext4/ext4_extents.h        2008-06-06 17:03:34.000000000 -0700
  18 +++ linux-2.6.26-rc5/fs/ext4/ext4_extents.h     2008-06-06 17:03:58.000000000 -0700
  19 @@ -212,6 +212,7 @@ static inline int ext4_ext_get_actual_le
  20                 (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
  21  }
  22
  23 +extern int ext4_ext_calc_metadata_amount(struct inode *inode, int blocks);
  24  extern ext4_fsblk_t idx_pblock(struct ext4_extent_idx *);
  25  extern void ext4_ext_store_pblock(struct ext4_extent *, ext4_fsblk_t);
  26  extern int ext4_extent_tree_init(handle_t *, struct inode *);
  27 Index: linux-2.6.26-rc5/fs/ext4/extents.c
  28 ===================================================================
  29 --- linux-2.6.26-rc5.orig/fs/ext4/extents.c     2008-06-06 17:03:51.000000000 -0700
  30 +++ linux-2.6.26-rc5/fs/ext4/extents.c  2008-06-06 17:03:58.000000000 -0700
  31 @@ -246,6 +246,36 @@ static int ext4_ext_space_root_idx(struc
  32         return size;
  33  }
  34
  35 +/*
  36 + * Calculate the number of metadata blocks needed
  37 + * to allocate @blocks
  38 + * Worse case is one block per extent
  39 + */
  40 +int ext4_ext_calc_metadata_amount(struct inode *inode, int blocks)
  41 +{
  42 +       int lcap, icap, rcap, leafs, idxs, num;
  43 +       int newextents = blocks;
  44 +
  45 +       rcap = ext4_ext_space_root_idx(inode);
  46 +       lcap = ext4_ext_space_block(inode);
  47 +       icap = ext4_ext_space_block_idx(inode);
  48 +
  49 +       /* number of new leaf blocks needed */
  50 +       num = leafs = (newextents + lcap - 1) / lcap;
  51 +
  52 +       /*
  53 +        * Worse case, we need separate index block(s)
  54 +        * to link all new leaf blocks
  55 +        */
  56 +       idxs = (leafs + icap - 1) / icap;
  57 +       do {
  58 +               num += idxs;
  59 +               idxs = (idxs + icap - 1) / icap;
  60 +       } while (idxs > rcap);
  61 +
  62 +       return num;
  63 +}
  64 +
  65  static int
  66  ext4_ext_max_entries(struct inode *inode, int depth)
  67  {