ocfs2: Add CoW support.

This patch try CoW support for a refcounted record.

the whole process will be:
1. Calculate how many clusters we need to CoW and where we start.
   Extents that are not completely encompassed by the write will
   be broken on 1MB boundaries.
2. Do CoW for the clusters with the help of page cache.
3. Change the b-tree structure with the new allocated clusters.

Signed-off-by: Tao Ma <tao.ma@oracle.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/ocfs2/alloc.h b/fs/ocfs2/alloc.h
index 19d5b88a93df..9c122d574464 100644
--- a/fs/ocfs2/alloc.h
+++ b/fs/ocfs2/alloc.h
@@ -271,6 +271,11 @@ static inline int ocfs2_is_empty_extent(struct ocfs2_extent_rec *rec)
         return !rec->e_leaf_clusters;
 }
 
+int ocfs2_grab_pages(struct inode *inode, loff_t start, loff_t end,
+                     struct page **pages, int *num);
+void ocfs2_map_and_dirty_page(struct inode *inode, handle_t *handle,
+                              unsigned int from, unsigned int to,
+                              struct page *page, int zero, u64 *phys);
 /*
  * Structures which describe a path through a btree, and functions to
  * manipulate them.