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btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots 

Relocation code will drop btrfs_root::reloc_root as soon as
merge_reloc_root() finishes.

However later qgroup code will need to access btrfs_root::reloc_root
after merge_reloc_root() for delayed subtree rescan.

So alter the timming of resetting btrfs_root:::reloc_root, make it
happens after transaction commit.

With this patch, we will introduce a new btrfs_root::state,
BTRFS_ROOT_DEAD_RELOC_TREE, to info part of btrfs_root::reloc_tree user
that although btrfs_root::reloc_tree is still non-NULL, but still it's
not used any more.

The lifespan of btrfs_root::reloc tree will become:
          Old behavior            |              New
------------------------------------------------------------------------
btrfs_init_reloc_root()      ---  | btrfs_init_reloc_root()      ---
  set reloc_root              |   |   set reloc_root              |
                              |   |                               |
                              |   |                               |
merge_reloc_root()            |   | merge_reloc_root()            |
|- btrfs_update_reloc_root() ---  | |- btrfs_update_reloc_root() -+-
     clear btrfs_root::reloc_root |      set ROOT_DEAD_RELOC_TREE |
                                  |      record root into dirty   |
                                  |      roots rbtree             |
                                  |                               |
                                  | reloc_block_group() Or        |
                                  | btrfs_recover_relocation()    |
                                  | | After transaction commit    |
                                  | |- clean_dirty_subvols()     ---
                                  |     clear btrfs_root::reloc_root

During ROOT_DEAD_RELOC_TREE set lifespan, the only user of
btrfs_root::reloc_tree should be qgroup.

Since reloc root needs a longer life-span, this patch will also delay
btrfs_drop_snapshot() call.
Now btrfs_drop_snapshot() is called in clean_dirty_subvols().

This patch will increase the size of btrfs_root by 16 bytes.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2019-01-23 15:15:14 +08:00 committed by David Sterba
parent 119e80df7d
commit d2311e6985
3 changed files with 84 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
fs/btrfs/ctree.h
View File

@ -1199,6 +1199,13 @@ enum {
BTRFS_ROOT_MULTI_LOG_TASKS,
BTRFS_ROOT_DIRTY,
BTRFS_ROOT_DELETING,
/*
* Reloc tree is orphan, only kept here for qgroup delayed subtree scan
*
* Set for the subvolume tree owning the reloc tree.
*/
BTRFS_ROOT_DEAD_RELOC_TREE,
};
/*
@ -1311,6 +1318,14 @@ struct btrfs_root {
struct list_head ordered_root;
u64 nr_ordered_extents;
/*
* Not empty if this subvolume root has gone through tree block swap
* (relocation)
*
* Will be used by reloc_control::dirty_subvol_roots.
*/
struct list_head reloc_dirty_list;
/*
* Number of currently running SEND ioctls to prevent
* manipulation with the read-only status via SUBVOL_SETFLAGS

1
fs/btrfs/disk-io.c
View File

@ -1176,6 +1176,7 @@ static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
INIT_LIST_HEAD(&root->delalloc_root);
INIT_LIST_HEAD(&root->ordered_extents);
INIT_LIST_HEAD(&root->ordered_root);
INIT_LIST_HEAD(&root->reloc_dirty_list);
INIT_LIST_HEAD(&root->logged_list[0]);
INIT_LIST_HEAD(&root->logged_list[1]);
spin_lock_init(&root->inode_lock);

85
fs/btrfs/relocation.c
View File

@ -162,6 +162,8 @@ struct reloc_control {
struct mapping_tree reloc_root_tree;
/* list of reloc trees */
struct list_head reloc_roots;
/* list of subvolume trees that get relocated */
struct list_head dirty_subvol_roots;
/* size of metadata reservation for merging reloc trees */
u64 merging_rsv_size;
/* size of relocated tree nodes */
@ -1467,15 +1469,17 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
struct btrfs_root_item *root_item;
int ret;
if (!root->reloc_root)
if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state) ||
!root->reloc_root)
goto out;
reloc_root = root->reloc_root;
root_item = &reloc_root->root_item;
/* root->reloc_root will stay until current relocation finished */
if (fs_info->reloc_ctl->merge_reloc_tree &&
btrfs_root_refs(root_item) == 0) {
root->reloc_root = NULL;
set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
__del_reloc_root(reloc_root);
}
@ -2120,6 +2124,58 @@ static int find_next_key(struct btrfs_path *path, int level,
return 1;
}
/*
* Insert current subvolume into reloc_control::dirty_subvol_roots
*/
static void insert_dirty_subvol(struct btrfs_trans_handle *trans,
struct reloc_control *rc,
struct btrfs_root *root)
{
struct btrfs_root *reloc_root = root->reloc_root;
struct btrfs_root_item *reloc_root_item;
/* @root must be a subvolume tree root with a valid reloc tree */
ASSERT(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
ASSERT(reloc_root);
reloc_root_item = &reloc_root->root_item;
memset(&reloc_root_item->drop_progress, 0,
sizeof(reloc_root_item->drop_progress));
reloc_root_item->drop_level = 0;
btrfs_set_root_refs(reloc_root_item, 0);
btrfs_update_reloc_root(trans, root);
if (list_empty(&root->reloc_dirty_list)) {
btrfs_grab_fs_root(root);
list_add_tail(&root->reloc_dirty_list, &rc->dirty_subvol_roots);
}
}
static int clean_dirty_subvols(struct reloc_control *rc)
{
struct btrfs_root *root;
struct btrfs_root *next;
int ret = 0;
list_for_each_entry_safe(root, next, &rc->dirty_subvol_roots,
reloc_dirty_list) {
struct btrfs_root *reloc_root = root->reloc_root;
clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
list_del_init(&root->reloc_dirty_list);
root->reloc_root = NULL;
if (reloc_root) {
int ret2;
ret2 = btrfs_drop_snapshot(reloc_root, NULL, 0, 1);
if (ret2 < 0 && !ret)
ret = ret2;
}
btrfs_put_fs_root(root);
}
return ret;
}
/*
* merge the relocated tree blocks in reloc tree with corresponding
* fs tree.
@ -2258,13 +2314,8 @@ static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
out:
btrfs_free_path(path);
if (err == 0) {
memset(&root_item->drop_progress, 0,
sizeof(root_item->drop_progress));
root_item->drop_level = 0;
btrfs_set_root_refs(root_item, 0);
btrfs_update_reloc_root(trans, root);
}
if (err == 0)
insert_dirty_subvol(trans, rc, root);
if (trans)
btrfs_end_transaction_throttle(trans);
@ -2409,14 +2460,6 @@ again:
} else {
list_del_init(&reloc_root->root_list);
}
ret = btrfs_drop_snapshot(reloc_root, rc->block_rsv, 0, 1);
if (ret < 0) {
if (list_empty(&reloc_root->root_list))
list_add_tail(&reloc_root->root_list,
&reloc_roots);
goto out;
}
}
if (found) {
@ -4078,6 +4121,9 @@ restart:
goto out_free;
}
btrfs_commit_transaction(trans);
ret = clean_dirty_subvols(rc);
if (ret < 0 && !err)
err = ret;
out_free:
btrfs_free_block_rsv(fs_info, rc->block_rsv);
btrfs_free_path(path);
@ -4172,6 +4218,7 @@ static struct reloc_control *alloc_reloc_control(void)
return NULL;
INIT_LIST_HEAD(&rc->reloc_roots);
INIT_LIST_HEAD(&rc->dirty_subvol_roots);
backref_cache_init(&rc->backref_cache);
mapping_tree_init(&rc->reloc_root_tree);
extent_io_tree_init(&rc->processed_blocks, NULL);
@ -4467,6 +4514,10 @@ int btrfs_recover_relocation(struct btrfs_root *root)
goto out_free;
}
err = btrfs_commit_transaction(trans);
ret = clean_dirty_subvols(rc);
if (ret < 0 && !err)
err = ret;
out_free:
kfree(rc);
out: