Commit c0f0a9e7 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

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: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent c0fab480

fs/btrfs/extent_io.c

+30 −20
Original line number Diff line number Diff line
@@ -5247,6 +5247,29 @@ struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info, 
}

#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)

{
@@ -5292,27 +5315,14 @@ 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)) {

		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;

		}

			exists = NULL;



			WARN_ON(PageDirty(p));

			detach_page_private(p);

		}

		attach_extent_buffer_page(eb, p);

		spin_unlock(&mapping->private_lock);

		WARN_ON(PageDirty(p));