1. 04 2月, 2009 1 次提交
    • C
      Btrfs: Make btrfs_drop_snapshot work in larger and more efficient chunks · bd56b302
      Chris Mason 提交于
      Every transaction in btrfs creates a new snapshot, and then schedules the
      snapshot from the last transaction for deletion.  Snapshot deletion
      works by walking down the btree and dropping the reference counts
      on each btree block during the walk.
      
      If if a given leaf or node has a reference count greater than one,
      the reference count is decremented and the subtree pointed to by that
      node is ignored.
      
      If the reference count is one, walking continues down into that node
      or leaf, and the references of everything it points to are decremented.
      
      The old code would try to work in small pieces, walking down the tree
      until it found the lowest leaf or node to free and then returning.  This
      was very friendly to the rest of the FS because it didn't have a huge
      impact on other operations.
      
      But it wouldn't always keep up with the rate that new commits added new
      snapshots for deletion, and it wasn't very optimal for the extent
      allocation tree because it wasn't finding leaves that were close together
      on disk and processing them at the same time.
      
      This changes things to walk down to a level 1 node and then process it
      in bulk.  All the leaf pointers are sorted and the leaves are dropped
      in order based on their extent number.
      
      The extent allocation tree and commit code are now fast enough for
      this kind of bulk processing to work without slowing the rest of the FS
      down.  Overall it does less IO and is better able to keep up with
      snapshot deletions under high load.
      Signed-off-by: NChris Mason <chris.mason@oracle.com>
      bd56b302
  2. 06 1月, 2009 1 次提交
  3. 30 9月, 2008 1 次提交
    • C
      Btrfs: add and improve comments · d352ac68
      Chris Mason 提交于
      This improves the comments at the top of many functions.  It didn't
      dive into the guts of functions because I was trying to
      avoid merging problems with the new allocator and back reference work.
      
      extent-tree.c and volumes.c were both skipped, and there is definitely
      more work todo in cleaning and commenting the code.
      Signed-off-by: NChris Mason <chris.mason@oracle.com>
      d352ac68
  4. 29 9月, 2008 1 次提交
    • C
      Btrfs: drop WARN_ON from btrfs_add_leaf_ref · 9a5e1ea1
      Chris Mason 提交于
      btrfs_add_leaf_ref was doing checks on the objects it found in the
      rbtree to make sure they were properly linked into the tree.  But, the field
      it was checking can be safely changed outside of the tree spin lock.
      
      The WARN_ON was for debugging the initial implementation and can be
      safely removed.
      Signed-off-by: NChris Mason <chris.mason@oracle.com>
      9a5e1ea1
  5. 26 9月, 2008 1 次提交
    • Z
      Btrfs: Add shared reference cache · e4657689
      Zheng Yan 提交于
      Btrfs has a cache of reference counts in leaves, allowing it to
      avoid reading tree leaves while deleting snapshots.  To reduce
      contention with multiple subvolumes, this cache is private to each
      subvolume.
      
      This patch adds shared reference cache support. The new space
      balancing code plays with multiple subvols at the same time, So
      the old per-subvol reference cache is not well suited.
      Signed-off-by: NChris Mason <chris.mason@oracle.com>
      e4657689
  6. 25 9月, 2008 3 次提交
    • Y
      Btrfs: implement memory reclaim for leaf reference cache · bcc63abb
      Yan 提交于
      The memory reclaiming issue happens when snapshot exists. In that
      case, some cache entries may not be used during old snapshot dropping,
      so they will remain in the cache until umount.
      
      The patch adds a field to struct btrfs_leaf_ref to record create time. Besides,
      the patch makes all dead roots of a given snapshot linked together in order of
      create time. After a old snapshot was completely dropped, we check the dead
      root list and remove all cache entries created before the oldest dead root in
      the list.
      Signed-off-by: NChris Mason <chris.mason@oracle.com>
      bcc63abb
    • C
      Btrfs: Leaf reference cache update · 017e5369
      Chris Mason 提交于
      This changes the reference cache to make a single cache per root
      instead of one cache per transaction, and to key by the byte number
      of the disk block instead of the keys inside.
      
      This makes it much less likely to have cache misses if a snapshot
      or something has an extra reference on a higher node or a leaf while
      the first transaction that added the leaf into the cache is dropping.
      
      Some throttling is added to functions that free blocks heavily so they
      wait for old transactions to drop.
      Signed-off-by: NChris Mason <chris.mason@oracle.com>
      017e5369
    • Y
      Btrfs: Add a leaf reference cache · 31153d81
      Yan Zheng 提交于
      Much of the IO done while dropping snapshots is done looking up
      leaves in the filesystem trees to see if they point to any extents and
      to drop the references on any extents found.
      
      This creates a cache so that IO isn't required.
      Signed-off-by: NChris Mason <chris.mason@oracle.com>
      31153d81