Commit 3628b4ca authored Oct 09, 2018 by Qu Wenruo Committed by David Sterba Oct 15, 2018

btrfs: qgroup: Avoid calling qgroup functions if qgroup is not enabled



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>

parent 0f375eed

fs/btrfs/qgroup.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -3521,6 +3521,10 @@ static int __btrfs_qgroup_release_data(struct inode *inode,
		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)

fs/btrfs/qgroup.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -255,6 +255,8 @@ void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info,
		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);

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