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Subject[PATCH 4.4 092/160] btrfs: qgroup: Dirty all qgroups before rescan
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Qu Wenruo <wqu@suse.com>

commit 9c7b0c2e8dbfbcd80a71e2cbfe02704f26c185c6 upstream.

[BUG]
In the following case, rescan won't zero out the number of qgroup 1/0:

$ mkfs.btrfs -fq $DEV
$ mount $DEV /mnt

$ btrfs quota enable /mnt
$ btrfs qgroup create 1/0 /mnt
$ btrfs sub create /mnt/sub
$ btrfs qgroup assign 0/257 1/0 /mnt

$ dd if=/dev/urandom of=/mnt/sub/file bs=1k count=1000
$ btrfs sub snap /mnt/sub /mnt/snap
$ btrfs quota rescan -w /mnt
$ btrfs qgroup show -pcre /mnt
qgroupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/5 16.00KiB 16.00KiB none none --- ---
0/257 1016.00KiB 16.00KiB none none 1/0 ---
0/258 1016.00KiB 16.00KiB none none --- ---
1/0 1016.00KiB 16.00KiB none none --- 0/257

So far so good, but:

$ btrfs qgroup remove 0/257 1/0 /mnt
WARNING: quotas may be inconsistent, rescan needed
$ btrfs quota rescan -w /mnt
$ btrfs qgroup show -pcre /mnt
qgoupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/5 16.00KiB 16.00KiB none none --- ---
0/257 1016.00KiB 16.00KiB none none --- ---
0/258 1016.00KiB 16.00KiB none none --- ---
1/0 1016.00KiB 16.00KiB none none --- ---
^^^^^^^^^^ ^^^^^^^^ not cleared

[CAUSE]
Before rescan we call qgroup_rescan_zero_tracking() to zero out all
qgroups' accounting numbers.

However we don't mark all qgroups dirty, but rely on rescan to do so.

If we have any high level qgroup without children, it won't be marked
dirty during rescan, since we cannot reach that qgroup.

This will cause QGROUP_INFO items of childless qgroups never get updated
in the quota tree, thus their numbers will stay the same in "btrfs
qgroup show" output.

[FIX]
Just mark all qgroups dirty in qgroup_rescan_zero_tracking(), so even if
we have childless qgroups, their QGROUP_INFO items will still get
updated during rescan.

Reported-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Tested-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/qgroup.c | 1 +
1 file changed, 1 insertion(+)

--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2446,6 +2446,7 @@ qgroup_rescan_zero_tracking(struct btrfs
qgroup->rfer_cmpr = 0;
qgroup->excl = 0;
qgroup->excl_cmpr = 0;
+ qgroup_dirty(fs_info, qgroup);
}
spin_unlock(&fs_info->qgroup_lock);
}

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