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[76.182.20.124]) by smtp.gmail.com with ESMTPSA id e3-20020a056902034300b00c3a96009bdfsm1772575ybs.35.2023.07.14.07.00.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Jul 2023 07:00:19 -0700 (PDT) Date: Fri, 14 Jul 2023 10:00:18 -0400 From: Josef Bacik To: fdmanana@kernel.org Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH v2] btrfs: fix warning when putting transaction with qgroups enabled after abort Message-ID: <20230714140018.GA466183@perftesting> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Jul 14, 2023 at 01:42:06PM +0100, fdmanana@kernel.org wrote: > From: Filipe Manana > > If we have a transaction abort with qgroups enabled we get a warning > triggered when doing the final put on the transaction, like this: > > [161552.678901] ------------[ cut here ]------------ > [161552.681530] WARNING: CPU: 4 PID: 81745 at fs/btrfs/transaction.c:144 btrfs_put_transaction+0x123/0x130 [btrfs] > [161552.681759] Modules linked in: btrfs blake2b_generic xor (...) > [161552.681934] CPU: 4 PID: 81745 Comm: btrfs-transacti Tainted: G W 6.4.0-rc6-btrfs-next-134+ #1 > [161552.681945] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 > [161552.681951] RIP: 0010:btrfs_put_transaction+0x123/0x130 [btrfs] > [161552.682139] Code: bd a0 01 00 (...) > [161552.682146] RSP: 0018:ffffa168c0527e28 EFLAGS: 00010286 > [161552.682155] RAX: ffff936042caed00 RBX: ffff93604a3eb448 RCX: 0000000000000000 > [161552.682161] RDX: ffff93606421b028 RSI: ffffffff92ff0878 RDI: ffff93606421b010 > [161552.682166] RBP: ffff93606421b000 R08: 0000000000000000 R09: ffffa168c0d07c20 > [161552.682171] R10: 0000000000000000 R11: ffff93608dc52950 R12: ffffa168c0527e70 > [161552.682175] R13: ffff93606421b000 R14: ffff93604a3eb420 R15: ffff93606421b028 > [161552.682181] FS: 0000000000000000(0000) GS:ffff93675fb00000(0000) knlGS:0000000000000000 > [161552.682187] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [161552.682193] CR2: 0000558ad262b000 CR3: 000000014feda005 CR4: 0000000000370ee0 > [161552.682211] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [161552.682216] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [161552.682221] Call Trace: > [161552.682229] > [161552.682236] ? __warn+0x80/0x130 > [161552.682250] ? btrfs_put_transaction+0x123/0x130 [btrfs] > [161552.682430] ? report_bug+0x1f4/0x200 > [161552.682444] ? handle_bug+0x42/0x70 > [161552.682456] ? exc_invalid_op+0x14/0x70 > [161552.682467] ? asm_exc_invalid_op+0x16/0x20 > [161552.682483] ? btrfs_put_transaction+0x123/0x130 [btrfs] > [161552.682661] btrfs_cleanup_transaction+0xe7/0x5e0 [btrfs] > [161552.682838] ? _raw_spin_unlock_irqrestore+0x23/0x40 > [161552.682847] ? try_to_wake_up+0x94/0x5e0 > [161552.682856] ? __pfx_process_timeout+0x10/0x10 > [161552.682872] transaction_kthread+0x103/0x1d0 [btrfs] > [161552.683047] ? __pfx_transaction_kthread+0x10/0x10 [btrfs] > [161552.683217] kthread+0xee/0x120 > [161552.683227] ? __pfx_kthread+0x10/0x10 > [161552.683237] ret_from_fork+0x29/0x50 > [161552.683259] > [161552.683262] ---[ 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") > Signed-off-by: Filipe Manana Reviewed-by: Josef Bacik Thanks, Josef