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  • Chris Mason's avatar
    Btrfs: New data=ordered implementation · e6dcd2dc
    Chris Mason authored
    The old data=ordered code would force commit to wait until
    all the data extents from the transaction were fully on disk.  This
    introduced large latencies into the commit and stalled new writers
    in the transaction for a long time.
    The new code changes the way data allocations and extents work:
    * When delayed allocation is filled, data extents are reserved, and
      the extent bit EXTENT_ORDERED is set on the entire range of the extent.
      A struct btrfs_ordered_extent is allocated an inserted into a per-inode
      rbtree to track the pending extents.
    * As each page is written EXTENT_ORDERED is cleared on the bytes corresponding
      to that page.
    * When all of the bytes corresponding to a single struct btrfs_ordered_extent
      are written, The previously reserved extent is inserted into the FS
      btree and into the extent allocation trees.  The checksums for the file
      data are also updated.
    Signed-off-by: default avatarChris Mason <>