ocfs2: make room for unwritten extents flag

Due to the size of our group bitmaps, we'll never have a leaf node extent
record with more than 16 bits worth of clusters. Split e_clusters up so that
leaf nodes can get a flags field where we can mark unwritten extents.
Interior nodes whose length references all the child nodes beneath it can't
split their e_clusters field, so we use a union to preserve sizing there.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/fs/ocfs2/alloc.h b/fs/ocfs2/alloc.h
index 3cb39cd5e478..fbcb5934a081 100644
--- a/fs/ocfs2/alloc.h
+++ b/fs/ocfs2/alloc.h
@@ -85,4 +85,23 @@ int ocfs2_commit_truncate(struct ocfs2_super *osb,
 int ocfs2_find_leaf(struct inode *inode, struct ocfs2_extent_list *root_el,
                     u32 cpos, struct buffer_head **leaf_bh);
 
+/*
+ * Helper function to look at the # of clusters in an extent record.
+ */
+static inline unsigned int ocfs2_rec_clusters(struct ocfs2_extent_list *el,
+                                              struct ocfs2_extent_rec *rec)
+{
+        /*
+         * Cluster count in extent records is slightly different
+         * between interior nodes and leaf nodes. This is to support
+         * unwritten extents which need a flags field in leaf node
+         * records, thus shrinking the available space for a clusters
+         * field.
+         */
+        if (el->l_tree_depth)
+                return le32_to_cpu(rec->e_int_clusters);
+        else
+                return le16_to_cpu(rec->e_leaf_clusters);
+}
+
 #endif /* OCFS2_ALLOC_H */