linux-kernel - Re: [RFC PATCH v2 0/2] block: fix backing_dev

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Date:   Wed, 25 Jan 2017 13:43:58 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Rabin Vincent <rabinv@...s.com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-block@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
        Wei Fang <fangwei1@...wei.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [RFC PATCH v2 0/2] block: fix backing_dev_info lifetime

On Mon, Jan 23, 2017 at 1:17 PM, Thiago Jung Bauermann
<bauerman@...ux.vnet.ibm.com> wrote:
> Hello Dan,
>
> Am Freitag, 6. Januar 2017, 17:02:51 BRST schrieb Dan Williams:
>> v1 of these changes [1] was a one line change to bdev_get_queue() to
>> prevent a shutdown crash when del_gendisk() races the final
>> __blkdev_put().
>>
>> While it is known at del_gendisk() time that the queue is still alive,
>> Jan Kara points to other paths [2] that are racing __blkdev_put() where
>> the assumption that ->bd_queue, or inode->i_wb is valid does not hold.
>>
>> Fix that broken assumption, make it the case that if you have a live
>> block_device, or block_device-inode that the corresponding queue and
>> inode-write-back data is still valid.
>>
>> These changes survive a run of the libnvdimm unit test suite which puts
>> some stress on the block_device shutdown path.
>
> I realize that the kernel test robot found problems with this series, but FWIW
> it fixes the bug mentioned in [2].
>

Thanks for the test result. I might take a look at cleaning up the
test robot reports and resubmitting this approach unless Jan beats me
to the punch with his backing_devi_info lifetime change patches.

>> [2]: http://www.spinics.net/lists/linux-fsdevel/msg105153.html