btrfs: qgroup: Avoid calling qgroup functions if qgroup is not enabled
authorQu Wenruo <wqu@suse.com>
Tue, 9 Oct 2018 06:36:45 +0000 (14:36 +0800)
committerDavid Sterba <dsterba@suse.com>
Mon, 15 Oct 2018 15:23:40 +0000 (17:23 +0200)
commit3628b4ca64f24a4ec55055597d0cb1c814729f8b
treee4848dbc56270ade0438975be2df36cf4c979476
parent0f375eed92b5a407657532637ed9652611a682f5
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>
fs/btrfs/qgroup.c
fs/btrfs/qgroup.h