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From: David Sterba <dsterba@suse.cz>
To: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Cc: dsterba@suse.cz, clm@fb.com, josef@toxicpanda.com,
	dsterba@suse.com, anand.jain@oracle.com,
	linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	skhan@linuxfoundation.org, gregkh@linuxfoundation.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com
Subject: Re: [PATCH v2] btrfs: fix rw device counting in __btrfs_free_extra_devids
Date: Thu, 19 Aug 2021 19:34:03 +0200	[thread overview]
Message-ID: <20210819173403.GI5047@twin.jikos.cz> (raw)
In-Reply-To: <89172356-335f-1ca3-d3a2-78fac7ef93fb@gmail.com>

On Fri, Aug 20, 2021 at 01:11:58AM +0800, Desmond Cheong Zhi Xi wrote:
> >>> The option #2 does not sound safe because the TGT bit is checked in
> >>> several places where device list is queried for various reasons, even
> >>> without a mounted filesystem.
> >>>
> >>> Removing the assertion makes more sense but I'm still not convinced that
> >>> the this is expected/allowed state of a closed device.
> >>>
> >>
> >> Would it be better if we cleared the REPLACE_TGT bit only when closing
> >> the device where device->devid == BTRFS_DEV_REPLACE_DEVID?
> >>
> >> The first conditional in btrfs_close_one_device assumes that we can come
> >> across such a device. If we come across it, we should properly reset it.
> >>
> >> If other devices has this bit set, the ASSERT will still catch it and
> >> let us know something is wrong.
> > 
> > That sounds great.
> > 
> >> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> >> index 70f94b75f25a..a5afebb78ecf 100644
> >> --- a/fs/btrfs/volumes.c
> >> +++ b/fs/btrfs/volumes.c
> >> @@ -1130,6 +1130,9 @@ static void btrfs_close_one_device(struct btrfs_device *device)
> >>                   fs_devices->rw_devices--;
> >>           }
> >>    
> >> +       if (device->devid == BTRFS_DEV_REPLACE_DEVID)
> >> +               clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
> >> +
> >>           if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
> >>                   fs_devices->missing_devices--;
> > 
> > I'll do a few test rounds, thanks.
> 
> Just following up. Did that resolve the issue or is further 
> investigation needed?

The fix seems to work, I haven't seen the assertion fail anymore,
incidentally the crash also stopped to show up on an unpatched branch.

  reply	other threads:[~2021-08-19 17:37 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27  7:13 Desmond Cheong Zhi Xi
2021-07-28 12:58 ` David Sterba
2021-08-12 10:38 ` David Sterba
2021-08-12 15:43   ` Desmond Cheong Zhi Xi
2021-08-12 15:50     ` David Sterba
2021-08-12 17:31       ` Desmond Cheong Zhi Xi
2021-08-13  8:51         ` David Sterba
2021-08-13  9:57           ` Desmond Cheong Zhi Xi
2021-08-13 10:30             ` David Sterba
2021-08-19 17:11               ` Desmond Cheong Zhi Xi
2021-08-19 17:34                 ` David Sterba [this message]
2021-08-20  3:09                   ` Desmond Cheong Zhi Xi
2021-08-20 10:58                     ` David Sterba
2021-08-20 17:53                       ` Desmond Cheong Zhi Xi

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