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nilfs2: add routines to roll back state of DAT file

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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>
This commit is contained in:
Ryusuke Konishi
2010-09-06 12:05:43 +09:00
parent a8070dd365
commit ebdfed4dc5
5 changed files with 145 additions and 19 deletions
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17
fs/nilfs2/btnode.c
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@@ -37,15 +37,7 @@
void nilfs_btnode_cache_init_once(struct address_space *btnc)
{
memset(btnc, 0, sizeof(*btnc));
INIT_RADIX_TREE(&btnc->page_tree, GFP_ATOMIC);
spin_lock_init(&btnc->tree_lock);
INIT_LIST_HEAD(&btnc->private_list);
spin_lock_init(&btnc->private_lock);
spin_lock_init(&btnc->i_mmap_lock);
INIT_RAW_PRIO_TREE_ROOT(&btnc->i_mmap);
INIT_LIST_HEAD(&btnc->i_mmap_nonlinear);
nilfs_mapping_init_once(btnc);
}
static const struct address_space_operations def_btnode_aops = {
@@ -55,12 +47,7 @@ static const struct address_space_operations def_btnode_aops = {
void nilfs_btnode_cache_init(struct address_space *btnc,
struct backing_dev_info *bdi)
{
btnc->host = NULL; /* can safely set to host inode ? */
btnc->flags = 0;
mapping_set_gfp_mask(btnc, GFP_NOFS);
btnc->assoc_mapping = NULL;
btnc->backing_dev_info = bdi;
btnc->a_ops = &def_btnode_aops;
nilfs_mapping_init(btnc, bdi, &def_btnode_aops);
}
void nilfs_btnode_cache_clear(struct address_space *btnc)