[PATCH 4.18 317/350] btrfs: qgroup: Avoid calling qgroup functions if qgroup is not enabled

Greg Kroah-Hartman
2018-11-11T23:11:13Z

From: Qu Wenruo <wqu@suse.com>

commit 3628b4ca64f24a4ec55055597d0cb1c814729f8b upstream.

Some qgroup trace events like btrfs_qgroup_release_data() and
btrfs_qgroup_free_delayed_ref() can still be triggered even if qgroup is
not enabled.

This is caused by the lack of qgroup status check before calling some
qgroup functions. Thankfully the functions can handle quota disabled
case well and just do nothing for qgroup disabled case.

This patch will do earlier check before triggering related trace events.

And for enabled <-> disabled race case:

1) For enabled->disabled case
Disable will wipe out all qgroups data including reservation and
excl/rfer. Even if we leak some reservation or numbers, it will
still be cleared, so nothing will go wrong.

2) For disabled -> enabled case
Current btrfs_qgroup_release_data() will use extent_io tree to ensure
we won't underflow reservation. And for delayed_ref we use
head->qgroup_reserved to record the reserved space, so in that case
head->qgroup_reserved should be 0 and we won't underflow.

CC: stable@vger.kernel.org # 4.14+
Reported-by: Chris Murphy <lists@colorremedies.com>
Link: https://lore.kernel.org/linux-btrfs/CAJCQCtQau7DtuUUeycCkZ36qjbKuxNzsgqJ7+sJ6W0dK_NLE3w@mail.gmail.com/
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/qgroup.c | 4 ++++
fs/btrfs/qgroup.h | 2 ++
2 files changed, 6 insertions(+)

--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -3065,6 +3065,10 @@ static int __btrfs_qgroup_release_data(s
int trace_op = QGROUP_RELEASE;
int ret;

+ if (!test_bit(BTRFS_FS_QUOTA_ENABLED,
+ &BTRFS_I(inode)->root->fs_info->flags))
+ return 0;
+
/* In release case, we shouldn't have @reserved */
WARN_ON(!free && reserved);
if (free && reserved)
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -261,6 +261,8 @@ void btrfs_qgroup_free_refroot(struct bt
static inline void btrfs_qgroup_free_delayed_ref(struct btrfs_fs_info *fs_info,
u64 ref_root, u64 num_bytes)
{
+ if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
+ return;
trace_btrfs_qgroup_free_delayed_ref(fs_info, ref_root, num_bytes);
btrfs_qgroup_free_refroot(fs_info, ref_root, num_bytes,
BTRFS_QGROUP_RSV_DATA);