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From:   Qu Wenruo <wqu@suse.com>
To:     linux-btrfs@vger.kernel.org
Subject: [PATCH] btrfs: qgroup: Don't scan leaf if we're modifying reloc tree
Date:   Thu, 13 Dec 2018 13:48:56 +0800
Message-Id: <20181213054856.22340-1-wqu@suse.com>
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Since reloc tree doesn't contribute to qgroup numbers, just skip them.

This should catch the final leakage of unnecessary data refs for qgroup.
The 4G data 16 snapshots test should explain it pretty well:

             | delayed subtree | refactor delayed ref | this patch (*)
---------------------------------------------------------------------
relocated    |           22653 |                22673 |         22744
qgroup dirty |          122792 |                48360 |            70
time         |          24.494 |               11.606 |         3.944

*: Needs to be applied upon delayed subtree scan and delayed ref
refactor patchsets.

Finally, we're at the stage where qgroup + metadata balance cost no
obvious overhead.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/extent-tree.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 26afed91bfb2..11d70de16bb7 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8773,11 +8773,13 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
 			else
 				ret = btrfs_dec_ref(trans, root, eb, 0);
 			BUG_ON(ret); /* -ENOMEM */
-			ret = btrfs_qgroup_trace_leaf_items(trans, eb);
-			if (ret) {
-				btrfs_err_rl(fs_info,
-					     "error %d accounting leaf items. Quota is out of sync, rescan required.",
+			if (is_fstree(root->root_key.objectid)) {
+				ret = btrfs_qgroup_trace_leaf_items(trans, eb);
+				if (ret) {
+					btrfs_err_rl(fs_info,
+"error %d accounting leaf items. Quota is out of sync, rescan required.",
 					     ret);
+				}
 			}
 		}
 		/* make block locked assertion in clean_tree_block happy */
-- 
2.19.2