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.c b/fs/nilfs2/mdt.c
index 73e5da3..0066468 100644
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -398,16 +398,22 @@
static int
nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
{
- struct inode *inode = container_of(page->mapping,
- struct inode, i_data);
- struct super_block *sb = inode->i_sb;
- struct the_nilfs *nilfs = NILFS_MDT(inode)->mi_nilfs;
+ struct inode *inode;
+ struct super_block *sb;
+ struct the_nilfs *nilfs;
struct nilfs_sb_info *writer = NULL;
int err = 0;
redirty_page_for_writepage(wbc, page);
unlock_page(page);
+ inode = page->mapping->host;
+ if (!inode)
+ return 0;
+
+ sb = inode->i_sb;
+ nilfs = NILFS_MDT(inode)->mi_nilfs;
+
if (page->mapping->assoc_mapping)
return 0; /* Do not request flush for shadow page cache */
if (!sb) {
@@ -567,6 +573,96 @@
&NILFS_I(orig)->i_btnode_cache;
}
+static const struct address_space_operations shadow_map_aops = {
+ .sync_page = block_sync_page,
+};
+
+/**
+ * nilfs_mdt_setup_shadow_map - setup shadow map and bind it to metadata file
+ * @inode: inode of the metadata file
+ * @shadow: shadow mapping
+ */
+int nilfs_mdt_setup_shadow_map(struct inode *inode,
+ struct nilfs_shadow_map *shadow)
+{
+ struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+ struct backing_dev_info *bdi = NILFS_I_NILFS(inode)->ns_bdi;
+
+ INIT_LIST_HEAD(&shadow->frozen_buffers);
+ nilfs_mapping_init_once(&shadow->frozen_data);
+ nilfs_mapping_init(&shadow->frozen_data, bdi, &shadow_map_aops);
+ nilfs_mapping_init_once(&shadow->frozen_btnodes);
+ nilfs_mapping_init(&shadow->frozen_btnodes, bdi, &shadow_map_aops);
+ mi->mi_shadow = shadow;
+ return 0;
+}
+
+/**
+ * nilfs_mdt_save_to_shadow_map - copy bmap and dirty pages to shadow map
+ * @inode: inode of the metadata file
+ */
+int nilfs_mdt_save_to_shadow_map(struct inode *inode)
+{
+ struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+ struct nilfs_inode_info *ii = NILFS_I(inode);
+ struct nilfs_shadow_map *shadow = mi->mi_shadow;
+ int ret;
+
+ ret = nilfs_copy_dirty_pages(&shadow->frozen_data, inode->i_mapping);
+ if (ret)
+ goto out;
+
+ ret = nilfs_copy_dirty_pages(&shadow->frozen_btnodes,
+ &ii->i_btnode_cache);
+ if (ret)
+ goto out;
+
+ nilfs_bmap_save(ii->i_bmap, &shadow->bmap_store);
+ out:
+ return ret;
+}
+
+/**
+ * nilfs_mdt_restore_from_shadow_map - restore dirty pages and bmap state
+ * @inode: inode of the metadata file
+ */
+void nilfs_mdt_restore_from_shadow_map(struct inode *inode)
+{
+ struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+ struct nilfs_inode_info *ii = NILFS_I(inode);
+ struct nilfs_shadow_map *shadow = mi->mi_shadow;
+
+ down_write(&mi->mi_sem);
+
+ if (mi->mi_palloc_cache)
+ nilfs_palloc_clear_cache(inode);
+
+ nilfs_clear_dirty_pages(inode->i_mapping);
+ nilfs_copy_back_pages(inode->i_mapping, &shadow->frozen_data);
+
+ nilfs_clear_dirty_pages(&ii->i_btnode_cache);
+ nilfs_copy_back_pages(&ii->i_btnode_cache, &shadow->frozen_btnodes);
+
+ nilfs_bmap_restore(ii->i_bmap, &shadow->bmap_store);
+
+ up_write(&mi->mi_sem);
+}
+
+/**
+ * nilfs_mdt_clear_shadow_map - truncate pages in shadow map caches
+ * @inode: inode of the metadata file
+ */
+void nilfs_mdt_clear_shadow_map(struct inode *inode)
+{
+ struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+ struct nilfs_shadow_map *shadow = mi->mi_shadow;
+
+ down_write(&mi->mi_sem);
+ truncate_inode_pages(&shadow->frozen_data, 0);
+ truncate_inode_pages(&shadow->frozen_btnodes, 0);
+ up_write(&mi->mi_sem);
+}
+
static void nilfs_mdt_clear(struct inode *inode)
{
struct nilfs_inode_info *ii = NILFS_I(inode);