Btrfs: cache extent state when writing out dirty metadata pages

Everytime we write out dirty pages we search for an offset in the tree,
convert the bits in the state, and then when we wait we search for the
offset again and clear the bits.  So for every dirty range in the io tree we
are doing 4 rb searches, which is suboptimal.  With this patch we are only
doing 2 searches for every cycle (modulo weird things happening).  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index a69dea219044..7aeb31087f88 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -233,13 +233,15 @@ int set_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
 int clear_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
                        gfp_t mask);
 int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
-                       int bits, int clear_bits, gfp_t mask);
+                       int bits, int clear_bits,
+                       struct extent_state **cached_state, gfp_t mask);
 int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
                         struct extent_state **cached_state, gfp_t mask);
 int set_extent_defrag(struct extent_io_tree *tree, u64 start, u64 end,
                       struct extent_state **cached_state, gfp_t mask);
 int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
-                          u64 *start_ret, u64 *end_ret, int bits);
+                          u64 *start_ret, u64 *end_ret, int bits,
+                          struct extent_state **cached_state);
 struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
                                                  u64 start, int bits);
 int extent_invalidatepage(struct extent_io_tree *tree,