btrfs: introduce helper to grab an existing extent buffer from a page

This patch will extract the code to grab an extent buffer from a page
into a helper, grab_extent_buffer_from_page().

This reduces one indent level, and provides the work place for later
expansion for subapge support.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 74c0a32..7f689ad 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5247,6 +5247,29 @@ free_eb:
 }
 #endif
 
+static struct extent_buffer *grab_extent_buffer(struct page *page)
+{
+       struct extent_buffer *exists;
+
+       /* Page not yet attached to an extent buffer */
+       if (!PagePrivate(page))
+               return NULL;
+
+       /*
+        * We could have already allocated an eb for this page and attached one
+        * so lets see if we can get a ref on the existing eb, and if we can we
+        * know it's good and we can just return that one, else we know we can
+        * just overwrite page->private.
+        */
+       exists = (struct extent_buffer *)page->private;
+       if (atomic_inc_not_zero(&exists->refs))
+               return exists;
+
+       WARN_ON(PageDirty(page));
+       detach_page_private(page);
+       return NULL;
+}
+
 struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
                                          u64 start, u64 owner_root, int level)
 {
@@ -5292,26 +5315,13 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
                }
 
                spin_lock(&mapping->private_lock);
-               if (PagePrivate(p)) {
-                       /*
-                        * We could have already allocated an eb for this page
-                        * and attached one so lets see if we can get a ref on
-                        * the existing eb, and if we can we know it's good and
-                        * we can just return that one, else we know we can just
-                        * overwrite page->private.
-                        */
-                       exists = (struct extent_buffer *)p->private;
-                       if (atomic_inc_not_zero(&exists->refs)) {
-                               spin_unlock(&mapping->private_lock);
-                               unlock_page(p);
-                               put_page(p);
-                               mark_extent_buffer_accessed(exists, p);
-                               goto free_eb;
-                       }
-                       exists = NULL;
-
-                       WARN_ON(PageDirty(p));
-                       detach_page_private(p);
+               exists = grab_extent_buffer(p);
+               if (exists) {
+                       spin_unlock(&mapping->private_lock);
+                       unlock_page(p);
+                       put_page(p);
+                       mark_extent_buffer_accessed(exists, p);
+                       goto free_eb;
                }
                attach_extent_buffer_page(eb, p);
                spin_unlock(&mapping->private_lock);