cache-extent-hole-in-extent-status-tree-for-ext4_da_map_blocks

   1 ext4: cache extent hole in extent status tree for ext4_da_map_blocks()
   2
   3 From: Zheng Liu <wenqing.lz@taobao.com>
   4
   5 Currently extent status tree doesn't cache extent hole when a write
   6 looks up in extent tree to make sure whether a block has been allocated
   7 or not.  In this case, we don't put extent hole in extent cache because
   8 later this extent might be removed and a new delayed extent might be
   9 added back.  But it will cause a defect when we do a lot of writes.
  10 If we don't put extent hole in extent cache, the following writes also
  11 need to access extent tree to look at whether or not a block has been
  12 allocated.  It brings a cache miss.  This commit fixes this defect.
  13 Meanwhile, if an inode has no any extent, this extent hole also will
  14 be cached.
  15
  16 Cc: Andreas Dilger <adilger.kernel@dilger.ca>
  17 Cc: Jan Kara <jack@suse.cz>
  18 Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
  19 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  20 ---
  21  fs/ext4/ext4.h              |    4 +---
  22  fs/ext4/extents.c           |   23 +++++++++--------------
  23  fs/ext4/inode.c             |    6 ++----
  24  include/trace/events/ext4.h |    3 +--
  25  4 files changed, 13 insertions(+), 23 deletions(-)
  26
  27 diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
  28 index 6f294d3..7df9220 100644
  29 --- a/fs/ext4/ext4.h
  30 +++ b/fs/ext4/ext4.h
  31 @@ -565,10 +565,8 @@ enum {
  32  #define EXT4_GET_BLOCKS_KEEP_SIZE              0x0080
  33         /* Do not take i_data_sem locking in ext4_map_blocks */
  34  #define EXT4_GET_BLOCKS_NO_LOCK                        0x0100
  35 -       /* Do not put hole in extent cache */
  36 -#define EXT4_GET_BLOCKS_NO_PUT_HOLE            0x0200
  37         /* Convert written extents to unwritten */
  38 -#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN      0x0400
  39 +#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN      0x0200
  40
  41  /*
  42   * The bit position of these flags must not overlap with any of the
  43 diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
  44 index 76c2df3..6463d34 100644
  45 --- a/fs/ext4/extents.c
  46 +++ b/fs/ext4/extents.c
  47 @@ -2284,16 +2284,15 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
  48                                 ext4_lblk_t block)
  49  {
  50         int depth = ext_depth(inode);
  51 -       unsigned long len = 0;
  52 -       ext4_lblk_t lblock = 0;
  53 +       unsigned long len;
  54 +       ext4_lblk_t lblock;
  55         struct ext4_extent *ex;
  56
  57         ex = path[depth].p_ext;
  58         if (ex == NULL) {
  59 -               /*
  60 -                * there is no extent yet, so gap is [0;-] and we
  61 -                * don't cache it
  62 -                */
  63 +               /* there is no extent yet, so gap is [0;-] */
  64 +               lblock = 0;
  65 +               len = EXT_MAX_BLOCKS;
  66                 ext_debug("cache gap(whole file):");
  67         } else if (block < le32_to_cpu(ex->ee_block)) {
  68                 lblock = block;
  69 @@ -2302,9 +2301,6 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
  70                                 block,
  71                                 le32_to_cpu(ex->ee_block),
  72                                  ext4_ext_get_actual_len(ex));
  73 -               if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
  74 -                       ext4_es_insert_extent(inode, lblock, len, ~0,
  75 -                                             EXTENT_STATUS_HOLE);
  76         } else if (block >= le32_to_cpu(ex->ee_block)
  77                         + ext4_ext_get_actual_len(ex)) {
  78                 ext4_lblk_t next;
  79 @@ -2318,14 +2314,14 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
  80                                 block);
  81                 BUG_ON(next == lblock);
  82                 len = next - lblock;
  83 -               if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
  84 -                       ext4_es_insert_extent(inode, lblock, len, ~0,
  85 -                                             EXTENT_STATUS_HOLE);
  86         } else {
  87                 BUG();
  88         }
  89
  90         ext_debug(" -> %u:%lu\n", lblock, len);
  91 +       if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
  92 +               ext4_es_insert_extent(inode, lblock, len, ~0,
  93 +                                     EXTENT_STATUS_HOLE);
  94  }
  95
  96  /*
  97 @@ -4362,8 +4358,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
  98                  * put just found gap into cache to speed up
  99                  * subsequent requests
 100                  */
 101 -               if ((flags & EXT4_GET_BLOCKS_NO_PUT_HOLE) == 0)
 102 -                       ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
 103 +               ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
 104                 goto out2;
 105         }
 106
 107 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
 108 index 367a60c..d1ad9f9 100644
 109 --- a/fs/ext4/inode.c
 110 +++ b/fs/ext4/inode.c
 111 @@ -1485,11 +1485,9 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 112                         map->m_flags |= EXT4_MAP_FROM_CLUSTER;
 113                 retval = 0;
 114         } else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
 115 -               retval = ext4_ext_map_blocks(NULL, inode, map,
 116 -                                            EXT4_GET_BLOCKS_NO_PUT_HOLE);
 117 +               retval = ext4_ext_map_blocks(NULL, inode, map, 0);
 118         else
 119 -               retval = ext4_ind_map_blocks(NULL, inode, map,
 120 -                                            EXT4_GET_BLOCKS_NO_PUT_HOLE);
 121 +               retval = ext4_ind_map_blocks(NULL, inode, map, 0);
 122
 123  add_delayed:
 124         if (retval == 0) {
 125 diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
 126 index ff4bd1b..9337d36 100644
 127 --- a/include/trace/events/ext4.h
 128 +++ b/include/trace/events/ext4.h
 129 @@ -43,8 +43,7 @@ struct extent_status;
 130         { EXT4_GET_BLOCKS_METADATA_NOFAIL,      "METADATA_NOFAIL" },    \
 131         { EXT4_GET_BLOCKS_NO_NORMALIZE,         "NO_NORMALIZE" },       \
 132         { EXT4_GET_BLOCKS_KEEP_SIZE,            "KEEP_SIZE" },          \
 133 -       { EXT4_GET_BLOCKS_NO_LOCK,              "NO_LOCK" },            \
 134 -       { EXT4_GET_BLOCKS_NO_PUT_HOLE,          "NO_PUT_HOLE" })
 135 +       { EXT4_GET_BLOCKS_NO_LOCK,              "NO_LOCK" })
 136
 137  #define show_mflags(flags) __print_flags(flags, "",    \
 138         { EXT4_MAP_NEW,         "N" },                  \
 139 --
 140 1.7.9.7
 141
 142