From 5edfd9fdc644bf426a8bf9192d9c1a3680d75862 Mon Sep 17 00:00:00 2001
From: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date: Mon, 27 Feb 2017 15:10:34 +0800
Patch-mainline: v4.13-rc1
Git-commit: 5edfd9fdc644bf426a8bf9192d9c1a3680d75862
References: dependency for bsc#1031392
Subject: [PATCH 1/6] btrfs: qgroup: Add quick exit for non-fs extents
Modify btrfs_qgroup_account_extent() to exit quicker for non-fs extents.
The quick exit condition is:
1) The extent belongs to a non-fs tree
Only fs-tree extents can affect qgroup numbers and is the only case
where extent can be shared between different trees.
Although strictly speaking extent in data-reloc or tree-reloc tree
can be shared, data/tree-reloc root won't appear in the result of
btrfs_find_all_roots(), so we can ignore such case.
So we can check the first root in old_roots/new_roots ulist.
- if we find the 1st root is a not a fs/subvol root, then we can skip
the extent
- if we find the 1st root is a fs/subvol root, then we must continue
calculation
OR
2) both 'nr_old_roots' and 'nr_new_roots' are 0
This means either such extent got allocated then freed in current
transaction or it's a new reloc tree extent, whose nr_new_roots is 0.
Either way it won't affect qgroup accounting and can be skipped
safely.
Such quick exit can make trace output more quite and less confusing:
(example with fs uuid and time stamp removed)
Before:
------
add_delayed_tree_ref: bytenr=29556736 num_bytes=16384 action=ADD_DELAYED_REF parent=0(-) ref_root=2(EXTENT_TREE) level=0 type=TREE_BLOCK_REF seq=0
btrfs_qgroup_account_extent: bytenr=29556736 num_bytes=16384 nr_old_roots=0 nr_new_roots=1
------
Extent tree block will trigger btrfs_qgroup_account_extent() trace point
while no qgroup number is changed, as extent tree won't affect qgroup
accounting.
After:
------
add_delayed_tree_ref: bytenr=29556736 num_bytes=16384 action=ADD_DELAYED_REF parent=0(-) ref_root=2(EXTENT_TREE) level=0 type=TREE_BLOCK_REF seq=0
------
Now such unrelated extent won't trigger btrfs_qgroup_account_extent()
trace point, making the trace less noisy.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
[ changelog and comment adjustments ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/qgroup.c | 43 +++++++++++++++++++++++++++++++++++++++++--
1 file changed, 41 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 7d16f0692d73..34116f6cb5d5 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1919,6 +1919,35 @@ static int qgroup_update_counters(struct btrfs_fs_info *fs_info,
return 0;
}
+/*
+ * Check if the @roots potentially is a list of fs tree roots
+ *
+ * Return 0 for definitely not a fs/subvol tree roots ulist
+ * Return 1 for possible fs/subvol tree roots in the list (considering an empty
+ * one as well)
+ */
+static int maybe_fs_roots(struct ulist *roots)
+{
+ struct ulist_node *unode;
+ struct ulist_iterator uiter;
+
+ /* Empty one, still possible for fs roots */
+ if (!roots || roots->nnodes == 0)
+ return 1;
+
+ ULIST_ITER_INIT(&uiter);
+ unode = ulist_next(roots, &uiter);
+ if (!unode)
+ return 1;
+
+ /*
+ * If it contains fs tree roots, then it must belong to fs/subvol
+ * trees.
+ * If it contains a non-fs tree, it won't be shared with fs/subvol trees.
+ */
+ return is_fstree(unode->val);
+}
+
int
btrfs_qgroup_account_extent(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info,
@@ -1935,10 +1964,20 @@ btrfs_qgroup_account_extent(struct btrfs_trans_handle *trans,
if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
return 0;
- if (new_roots)
+ if (new_roots) {
+ if (!maybe_fs_roots(new_roots))
+ goto out_free;
nr_new_roots = new_roots->nnodes;
- if (old_roots)
+ }
+ if (old_roots) {
+ if (!maybe_fs_roots(old_roots))
+ goto out_free;
nr_old_roots = old_roots->nnodes;
+ }
+
+ /* Quick exit, either not fs tree roots, or won't affect any qgroup */
+ if (nr_old_roots == 0 && nr_new_roots == 0)
+ goto out_free;
BUG_ON(!fs_info->quota_root);
--
2.19.0