miscellaneous-partial-cluster-cleanups

   1 ext4: miscellaneous partial cluster cleanups
   2
   3 From: Eric Whitney <enwlinux@gmail.com>
   4
   5 Add some casts and rearrange a few statements for improved readability.
   6 Some code can also be simplified and made more readable if we set
   7 partial_cluster to 0 rather than to a negative value when we can tell
   8 we've hit the left edge of the punched region.
   9
  10 Signed-off-by: Eric Whitney <enwlinux@gmail.com>
  11 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  12 ---
  13  fs/ext4/extents.c | 39 +++++++++++++++++++++------------------
  14  1 file changed, 21 insertions(+), 18 deletions(-)
  15
  16 diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
  17 index 859ab37..841adf0 100644
  18 --- a/fs/ext4/extents.c
  19 +++ b/fs/ext4/extents.c
  20 @@ -2481,7 +2481,7 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
  21                               ext4_lblk_t from, ext4_lblk_t to)
  22  {
  23         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  24 -       unsigned short ee_len =  ext4_ext_get_actual_len(ex);
  25 +       unsigned short ee_len = ext4_ext_get_actual_len(ex);
  26         ext4_fsblk_t pblk;
  27         int flags = get_default_free_blocks_flags(inode);
  28
  29 @@ -2490,7 +2490,7 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
  30          * at the beginning of the extent.  Instead, we make a note
  31          * that we tried freeing the cluster, and check to see if we
  32          * need to free it on a subsequent call to ext4_remove_blocks,
  33 -        * or at the end of the ext4_truncate() operation.
  34 +        * or at the end of ext4_ext_rm_leaf or ext4_ext_remove_space.
  35          */
  36         flags |= EXT4_FREE_BLOCKS_NOFREE_FIRST_CLUSTER;
  37
  38 @@ -2501,8 +2501,8 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
  39          * partial cluster here.
  40          */
  41         pblk = ext4_ext_pblock(ex) + ee_len - 1;
  42 -       if ((*partial_cluster > 0) &&
  43 -           (EXT4_B2C(sbi, pblk) != *partial_cluster)) {
  44 +       if (*partial_cluster > 0 &&
  45 +           *partial_cluster != (long long) EXT4_B2C(sbi, pblk)) {
  46                 ext4_free_blocks(handle, inode, NULL,
  47                                  EXT4_C2B(sbi, *partial_cluster),
  48                                  sbi->s_cluster_ratio, flags);
  49 @@ -2528,7 +2528,7 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
  50             && to == le32_to_cpu(ex->ee_block) + ee_len - 1) {
  51                 /* tail removal */
  52                 ext4_lblk_t num;
  53 -               unsigned int unaligned;
  54 +               long long first_cluster;
  55
  56                 num = le32_to_cpu(ex->ee_block) + ee_len - from;
  57                 pblk = ext4_ext_pblock(ex) + ee_len - num;
  58 @@ -2538,7 +2538,7 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
  59                  * used by any other extent (partial_cluster is negative).
  60                  */
  61                 if (*partial_cluster < 0 &&
  62 -                   -(*partial_cluster) == EXT4_B2C(sbi, pblk + num - 1))
  63 +                   *partial_cluster == -(long long) EXT4_B2C(sbi, pblk+num-1))
  64                         flags |= EXT4_FREE_BLOCKS_NOFREE_LAST_CLUSTER;
  65
  66                 ext_debug("free last %u blocks starting %llu partial %lld\n",
  67 @@ -2549,21 +2549,24 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
  68                  * beginning of a cluster, and we removed the entire
  69                  * extent and the cluster is not used by any other extent,
  70                  * save the partial cluster here, since we might need to
  71 -                * delete if we determine that the truncate operation has
  72 -                * removed all of the blocks in the cluster.
  73 +                * delete if we determine that the truncate or punch hole
  74 +                * operation has removed all of the blocks in the cluster.
  75 +                * If that cluster is used by another extent, preserve its
  76 +                * negative value so it isn't freed later on.
  77                  *
  78 -                * On the other hand, if we did not manage to free the whole
  79 -                * extent, we have to mark the cluster as used (store negative
  80 -                * cluster number in partial_cluster).
  81 +                * If the whole extent wasn't freed, we've reached the
  82 +                * start of the truncated/punched region and have finished
  83 +                * removing blocks.  If there's a partial cluster here it's
  84 +                * shared with the remainder of the extent and is no longer
  85 +                * a candidate for removal.
  86                  */
  87 -               unaligned = EXT4_PBLK_COFF(sbi, pblk);
  88 -               if (unaligned && (ee_len == num) &&
  89 -                   (*partial_cluster != -((long long)EXT4_B2C(sbi, pblk))))
  90 -                       *partial_cluster = EXT4_B2C(sbi, pblk);
  91 -               else if (unaligned)
  92 -                       *partial_cluster = -((long long)EXT4_B2C(sbi, pblk));
  93 -               else if (*partial_cluster > 0)
  94 +               if (EXT4_PBLK_COFF(sbi, pblk) && ee_len == num) {
  95 +                       first_cluster = (long long) EXT4_B2C(sbi, pblk);
  96 +                       if (first_cluster != -*partial_cluster)
  97 +                               *partial_cluster = first_cluster;
  98 +               } else {
  99                         *partial_cluster = 0;
 100 +               }
 101         } else
 102                 ext4_error(sbi->s_sb, "strange request: removal(2) "
 103                            "%u-%u from %u:%u\n",
 104 --
 105 1.9.1
 106
 107