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Commit 1625f8ac authored by Joel Becker's avatar Joel Becker Committed by Mark Fasheh
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ocfs2: Comment struct ocfs2_extent_tree_operations. 



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: default avatarJoel Becker <joel.becker@oracle.com>
Signed-off-by: default avatarMark Fasheh <mfasheh@suse.com>
parent f99b9b7c

fs/ocfs2/alloc.c

+43 −2
Original line number Diff line number Diff line
@@ -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);

};