linux-kernel - Re: [PATCH v3] block: fix incorrect references to disk objects

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Message-ID: <d5b9a684-2405-7db8-02ab-8ebc93c40fd5@kernel.dk>
Date:   Mon, 25 Oct 2021 07:44:07 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Zqiang <qiang.zhang1211@...il.com>,
        Matthew Wilcox <willy@...radead.org>
Cc:     hch@....de, sunhao.th@...il.com, hch@...radead.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] block: fix incorrect references to disk objects

On 10/25/21 2:27 AM, Zqiang wrote:
> 
> On 2021/10/18 下午8:26, Matthew Wilcox wrote:
>> On Mon, Oct 18, 2021 at 07:58:07PM +0800, Zqiang wrote:
>>> When adding partitions to the disk, the reference count of the disk
>>> object is increased. then alloc partition device and called
>>> device_add(), if the device_add() return error, the reference
>>> count of the disk object will be reduced twice, at put_device(pdev)
>>> and put_disk(disk). this leads to the end of the object's life cycle
>>> prematurely, and trigger following calltrace.
>>>
>>>    __init_work+0x2d/0x50 kernel/workqueue.c:519
>>>    synchronize_rcu_expedited+0x3af/0x650 kernel/rcu/tree_exp.h:847
>>>    bdi_remove_from_list mm/backing-dev.c:938 [inline]
>>>    bdi_unregister+0x17f/0x5c0 mm/backing-dev.c:946
>>>    release_bdi+0xa1/0xc0 mm/backing-dev.c:968
>>>    kref_put include/linux/kref.h:65 [inline]
>>>    bdi_put+0x72/0xa0 mm/backing-dev.c:976
>>>    bdev_free_inode+0x11e/0x220 block/bdev.c:408
>>>    i_callback+0x3f/0x70 fs/inode.c:226
>>>    rcu_do_batch kernel/rcu/tree.c:2508 [inline]
>>>    rcu_core+0x76d/0x16c0 kernel/rcu/tree.c:2743
>>>    __do_softirq+0x1d7/0x93b kernel/softirq.c:558
>>>    invoke_softirq kernel/softirq.c:432 [inline]
>>>    __irq_exit_rcu kernel/softirq.c:636 [inline]
>>>    irq_exit_rcu+0xf2/0x130 kernel/softirq.c:648
>>>    sysvec_apic_timer_interrupt+0x93/0xc0
>>>
>>> Return directly after calling the put_device().
>>>
>>> Reported-by: Hao Sun <sunhao.th@...il.com>
>>> Signed-off-by: Zqiang <qiang.zhang1211@...il.com>
>> Fixes: 9d3b8813895d ("block: change the refcounting for partitions")
>> Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> 
> Hello Jens Axboe
> 
> The patch description information of the previous v2 version is 
> incorrect, v3 modified the description information, please applied the 
> v3 version.

This patch is already upstream, I don't have a time machine...

-- 
Jens Axboe