If we have a transaction abort with qgroups enabled we get a warning
triggered when doing the final put on the transaction, like this:
[552.6789] ------------[ cut here ]------------
[552.6815] WARNING: CPU: 4 PID: 81745 at fs/btrfs/transaction.c:144 btrfs_put_transaction+0x123/0x130 [btrfs]
[552.6817] Modules linked in: btrfs blake2b_generic xor (...)
[552.6819] CPU: 4 PID: 81745 Comm: btrfs-transacti Tainted: G W 6.4.0-rc6-btrfs-next-134+ #1
[552.6819] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
[552.6819] RIP: 0010:btrfs_put_transaction+0x123/0x130 [btrfs]
[552.6821] Code: bd a0 01 00 (...)
[552.6821] RSP: 0018:
ffffa168c0527e28 EFLAGS:
00010286
[552.6821] RAX:
ffff936042caed00 RBX:
ffff93604a3eb448 RCX:
0000000000000000
[552.6821] RDX:
ffff93606421b028 RSI:
ffffffff92ff0878 RDI:
ffff93606421b010
[552.6821] RBP:
ffff93606421b000 R08:
0000000000000000 R09:
ffffa168c0d07c20
[552.6821] R10:
0000000000000000 R11:
ffff93608dc52950 R12:
ffffa168c0527e70
[552.6821] R13:
ffff93606421b000 R14:
ffff93604a3eb420 R15:
ffff93606421b028
[552.6821] FS:
0000000000000000(0000) GS:
ffff93675fb00000(0000) knlGS:
0000000000000000
[552.6821] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
[552.6821] CR2:
0000558ad262b000 CR3:
000000014feda005 CR4:
0000000000370ee0
[552.6822] DR0:
0000000000000000 DR1:
0000000000000000 DR2:
0000000000000000
[552.6822] DR3:
0000000000000000 DR6:
00000000fffe0ff0 DR7:
0000000000000400
[552.6822] Call Trace:
[552.6822] <TASK>
[552.6822] ? __warn+0x80/0x130
[552.6822] ? btrfs_put_transaction+0x123/0x130 [btrfs]
[552.6824] ? report_bug+0x1f4/0x200
[552.6824] ? handle_bug+0x42/0x70
[552.6824] ? exc_invalid_op+0x14/0x70
[552.6824] ? asm_exc_invalid_op+0x16/0x20
[552.6824] ? btrfs_put_transaction+0x123/0x130 [btrfs]
[552.6826] btrfs_cleanup_transaction+0xe7/0x5e0 [btrfs]
[552.6828] ? _raw_spin_unlock_irqrestore+0x23/0x40
[552.6828] ? try_to_wake_up+0x94/0x5e0
[552.6828] ? __pfx_process_timeout+0x10/0x10
[552.6828] transaction_kthread+0x103/0x1d0 [btrfs]
[552.6830] ? __pfx_transaction_kthread+0x10/0x10 [btrfs]
[552.6832] kthread+0xee/0x120
[552.6832] ? __pfx_kthread+0x10/0x10
[552.6832] ret_from_fork+0x29/0x50
[552.6832] </TASK>
[552.6832] ---[ end trace
0000000000000000 ]---
This corresponds to this line of code:
void btrfs_put_transaction(struct btrfs_transaction *transaction)
{
(...)
WARN_ON(!RB_EMPTY_ROOT(
&transaction->delayed_refs.dirty_extent_root));
(...)
}
The warning happens because btrfs_qgroup_destroy_extent_records(), called
in the transaction abort path, we free all entries from the rbtree
"dirty_extent_root" with rbtree_postorder_for_each_entry_safe(), but we
don't actually empty the rbtree - it's still pointing to nodes that were
freed.
So set the rbtree's root node to NULL to avoid this warning (assign
RB_ROOT).
Fixes: 81f7eb00ff5b ("btrfs: destroy qgroup extent records on transaction abort")
CC: stable@vger.kernel.org # 5.10+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>