linux-kernel - Re: 回复: 回复: [PATCH] btrfs: Fix missing close devices

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Message-ID: <SN4PR0401MB359872451E6F7B11AF1435B09B380@SN4PR0401MB3598.namprd04.prod.outlook.com>
Date:   Wed, 23 Sep 2020 08:17:07 +0000
From:   Johannes Thumshirn <Johannes.Thumshirn@....com>
To:     "Zhang, Qiang" <Qiang.Zhang@...driver.com>,
        "clm@...com" <clm@...com>,
        "josef@...icpanda.com" <josef@...icpanda.com>,
        "dsterba@...e.com" <dsterba@...e.com>,
        "syzbot+582e66e5edf36a22c7b0@...kaller.appspotmail.com" 
        <syzbot+582e66e5edf36a22c7b0@...kaller.appspotmail.com>
CC:     "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 回复: 回复: [PATCH] btrfs: Fix missing close devices

On 23/09/2020 08:03, Zhang, Qiang wrote:
> Hello Johannes Thumshirn
> 
> the crash happend in "snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev)" in btrfs_mount_root func,  the  "bdev" may be destroyed in btrfs_close_devices.
> I think add  btrfs_close_devices func before deactivate_locked_super is reasonable.
>  I'm not sure if that's another problem .
>  What's your point of view ？
> 

I think this is generally unneeded.
Think of this call chain:
deactivate_locked_super()
`-> fs->kill_sb()
    `-> btrfs_kill_super()
        `-> kill_anon_super()
            `-> generic_shutdown_super()
                `-> sop->put_super()
                    `-> btrfs_put_super()
                        `-> close_ctree()
                            `-> btrfs_close_devices()