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>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fecc64d..dd0ccc6 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -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,
};
/*
@@ -1312,6 +1319,14 @@ struct btrfs_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
*/