[PATCH 1/2] btrfs: restructure try_release_extent_buffer()

[Miao Xie <miaox@cn.fujitsu.com>]

restructure try_release_extent_buffer() and write a function to release the
extent buffer. It will be used later.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
  fs/btrfs/extent_io.c |   48 +++++++++++++++++++++++++++++++++++++-----------
  1 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 41277d6..70b7cc5 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3097,6 +3097,39 @@ static void __free_extent_buffer(struct extent_buffer *eb)
  	kmem_cache_free(extent_buffer_cache, eb);
  }
  
+/*
+ * Helper for releasing extent buffer page.
+ */
+static void btrfs_release_extent_buffer_page(struct extent_buffer *eb,
+						unsigned long start_idx)
+{
+	unsigned long index;
+	struct page *page;
+
+	if (!eb->first_page)
+		return;
+
+	index = num_extent_pages(eb->start, eb->len);
+	if (start_idx >= index)
+		return;
+
+	do {
+		index--;
+		page = extent_buffer_page(eb, index);
+		if (page)
+			page_cache_release(page);
+	} while (index != start_idx);
+}
+
+/*
+ * Helper for releasing the extent buffer.
+ */
+static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
+{
+	btrfs_release_extent_buffer_page(eb, 0);
+	__free_extent_buffer(eb);
+}
+
  struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
  					  u64 start, unsigned long len,
  					  struct page *page0,
@@ -3174,10 +3207,7 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
  free_eb:
  	if (!atomic_dec_and_test(&eb->refs))
  		return exists;
-	for (index = 1; index < i; index++)
-		page_cache_release(extent_buffer_page(eb, index));
-	page_cache_release(extent_buffer_page(eb, 0));
-	__free_extent_buffer(eb);
+	btrfs_release_extent_buffer(eb);
  	return exists;
  }
  
@@ -3831,8 +3861,6 @@ int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
  	u64 start = page_offset(page);
  	struct extent_buffer *eb;
  	int ret = 1;
-	unsigned long i;
-	unsigned long num_pages;
  
  	spin_lock(&tree->buffer_lock);
  	eb = buffer_search(tree, start);
@@ -3847,12 +3875,10 @@ int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
  		ret = 0;
  		goto out;
  	}
-	/* at this point we can safely release the extent buffer */
-	num_pages = num_extent_pages(eb->start, eb->len);
-	for (i = 0; i < num_pages; i++)
-		page_cache_release(extent_buffer_page(eb, i));
+
  	rb_erase(&eb->rb_node, &tree->buffer);
-	__free_extent_buffer(eb);
+	/* at this point we can safely release the extent buffer */
+	btrfs_release_extent_buffer(eb);
  out:
  	spin_unlock(&tree->buffer_lock);
  	return ret;
-- 
1.7.0.1