Btrfs: extent_io and extent_state optimizations

The end_bio routines are changed to take a pointer to the extent state
struct, and the state tree is walked in order to set/clear appropriate
bits as IO completes.  This greatly reduces the number of rbtree searches
done by the end_bio handlers, and reduces lock contention.

The extent_io releasepage function is changed to avoid expensive searches
for locked state.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 06be1fe84b29..f1e8bf251f32 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -23,19 +23,23 @@
 #define EXTENT_PAGE_PRIVATE 1
 #define EXTENT_PAGE_PRIVATE_FIRST_PAGE 3
 
+struct extent_state;
+
 struct extent_io_ops {
         int (*fill_delalloc)(struct inode *inode, u64 start, u64 end);
         int (*writepage_io_hook)(struct page *page, u64 start, u64 end);
         int (*readpage_io_hook)(struct page *page, u64 start, u64 end);
-        int (*readpage_end_io_hook)(struct page *page, u64 start, u64 end);
-        void (*writepage_end_io_hook)(struct page *page, u64 start, u64 end);
+        int (*readpage_end_io_hook)(struct page *page, u64 start, u64 end,
+                                    struct extent_state *state);
+        void (*writepage_end_io_hook)(struct page *page, u64 start, u64 end,
+                                      struct extent_state *state);
 };
 
 struct extent_io_tree {
         struct rb_root state;
         struct address_space *mapping;
         u64 dirty_bytes;
-        rwlock_t lock;
+        spinlock_t lock;
         struct extent_io_ops *ops;
         spinlock_t lru_lock;
         struct list_head buffer_lru;
@@ -45,8 +49,8 @@ struct extent_io_tree {
 struct extent_state {
         u64 start;
         u64 end; /* inclusive */
-        int in_tree;
         struct rb_node rb_node;
+        struct extent_io_tree *tree;
         wait_queue_head_t wq;
         atomic_t refs;
         unsigned long state;
@@ -82,7 +86,8 @@ void extent_io_tree_init(struct extent_io_tree *tree,
                           struct address_space *mapping, gfp_t mask);
 void extent_io_tree_empty_lru(struct extent_io_tree *tree);
 int try_release_extent_mapping(struct extent_map_tree *map,
-                               struct extent_io_tree *tree, struct page *page);
+                               struct extent_io_tree *tree, struct page *page,
+                               gfp_t mask);
 int lock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask);
 int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask);
 int extent_read_full_page(struct extent_io_tree *tree, struct page *page,