[PATCH 32/39] ocfs2: Comment struct ocfs2_extent_tree_operations.

Mark Fasheh
2008-09-24T22:10:48Z

From: Joel Becker <joel.becker@oracle.com>

struct ocfs2_extent_tree_operations provides methods for the different
on-disk btrees in ocfs2. Describing what those methods do is probably a
good idea.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
---
fs/ocfs2/alloc.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index d196d40..51c3183 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -50,21 +50,62 @@
#include "buffer_head_io.h"

+/*
+ * Operations for a specific extent tree type.
+ *
+ * To implement an on-disk btree (extent tree) type in ocfs2, add
+ * an ocfs2_extent_tree_operations structure and the matching
+ * ocfs2_get_<thingy>_extent_tree() function. That's pretty much it
+ * for the allocation portion of the extent tree.
+ */
struct ocfs2_extent_tree_operations {
+ /*
+ * last_eb_blk is the block number of the right most leaf extent
+ * block. Most on-disk structures containing an extent tree store
+ * this value for fast access. The ->eo_set_last_eb_blk() and
+ * ->eo_get_last_eb_blk() operations access this value. They are
+ * both required.
+ */
void (*eo_set_last_eb_blk)(struct ocfs2_extent_tree *et,
u64 blkno);
u64 (*eo_get_last_eb_blk)(struct ocfs2_extent_tree *et);
+
+ /*
+ * The on-disk structure usually keeps track of how many total
+ * clusters are stored in this extent tree. This function updates
+ * that value. new_clusters is the delta, and must be
+ * added to the total. Required.
+ */
void (*eo_update_clusters)(struct inode *inode,
struct ocfs2_extent_tree *et,
u32 new_clusters);
+
+ /*
+ * If ->eo_insert_check() exists, it is called before rec is
+ * inserted into the extent tree. It is optional.
+ */
int (*eo_insert_check)(struct inode *inode,
struct ocfs2_extent_tree *et,
struct ocfs2_extent_rec *rec);
int (*eo_sanity_check)(struct inode *inode, struct ocfs2_extent_tree *et);

- /* These are internal to ocfs2_extent_tree and don't have
- * accessor functions */
+ /*
+ * --------------------------------------------------------------
+ * The remaining are internal to ocfs2_extent_tree and don't have
+ * accessor functions
+ */
+
+ /*
+ * ->eo_fill_root_el() takes et->et_object and sets et->et_root_el.
+ * It is required.
+ */
void (*eo_fill_root_el)(struct ocfs2_extent_tree *et);
+
+ /*
+ * ->eo_fill_max_leaf_clusters sets et->et_max_leaf_clusters if
+ * it exists. If it does not, et->et_max_leaf_clusters is set
+ * to 0 (unlimited). Optional.
+ */
void (*eo_fill_max_leaf_clusters)(struct inode *inode,
struct ocfs2_extent_tree *et);
};
--
1.5.4.5