nilfs2: add routines to roll back state of DAT file
This adds optional function to metadata files which makes a copy of
bmap, page caches, and b-tree node cache, and rolls back to the copy
as needed.
This enhancement is intended to displace gcdat inode that provides a
similar function in a different way.
In this patch, nilfs_shadow_map structure is added to store a copy of
the foregoing states. nilfs_mdt_setup_shadow_map relates this
structure to a metadata file. And, nilfs_mdt_save_to_shadow_map() and
nilfs_mdt_restore_from_shadow_map() provides save and restore
functions respectively. Finally, nilfs_mdt_clear_shadow_map() clears
states of nilfs_shadow_map.
The copy of b-tree node cache and page cache is made by duplicating
only dirty pages into corresponding caches in nilfs_shadow_map. Their
restoration is done by clearing dirty pages from original caches and
by copying dirty pages back from nilfs_shadow_map.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/mdt.h b/fs/nilfs2/mdt.h
index f445602..e7f0d15 100644
--- a/fs/nilfs2/mdt.h
+++ b/fs/nilfs2/mdt.h
@@ -28,6 +28,13 @@
#include "nilfs.h"
#include "page.h"
+struct nilfs_shadow_map {
+ struct nilfs_bmap_store bmap_store;
+ struct address_space frozen_data;
+ struct address_space frozen_btnodes;
+ struct list_head frozen_buffers;
+};
+
/**
* struct nilfs_mdt_info - on-memory private data of meta data files
* @mi_nilfs: back pointer to the_nilfs struct
@@ -37,6 +44,7 @@
* @mi_first_entry_offset: offset to the first entry
* @mi_entries_per_block: number of entries in a block
* @mi_palloc_cache: persistent object allocator cache
+ * @mi_shadow: shadow of bmap and page caches
* @mi_blocks_per_group: number of blocks in a group
* @mi_blocks_per_desc_block: number of blocks per descriptor block
*/
@@ -48,6 +56,7 @@
unsigned mi_first_entry_offset;
unsigned long mi_entries_per_block;
struct nilfs_palloc_cache *mi_palloc_cache;
+ struct nilfs_shadow_map *mi_shadow;
unsigned long mi_blocks_per_group;
unsigned long mi_blocks_per_desc_block;
};
@@ -86,6 +95,11 @@
void nilfs_mdt_set_entry_size(struct inode *, unsigned, unsigned);
void nilfs_mdt_set_shadow(struct inode *, struct inode *);
+int nilfs_mdt_setup_shadow_map(struct inode *inode,
+ struct nilfs_shadow_map *shadow);
+int nilfs_mdt_save_to_shadow_map(struct inode *inode);
+void nilfs_mdt_restore_from_shadow_map(struct inode *inode);
+void nilfs_mdt_clear_shadow_map(struct inode *inode);
#define nilfs_mdt_mark_buffer_dirty(bh) nilfs_mark_buffer_dirty(bh)