Btrfs: restructure try_release_extent_buffer()

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

1 files changed, 37 insertions, 11 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d74e6af9b53a..6e3b326346a7 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3104,6 +3104,39 @@ 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,
@@ -3181,10 +3214,7 @@ 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;
 }
 
@@ -3838,8 +3868,6 @@ 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);
@@ -3854,12 +3882,10 @@ 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;