Re: [PATCH v2] btrfs: fix rw device counting in __btrfs_free_extra_devids

[Desmond Cheong Zhi Xi]

On 20/8/21 1:34 am, David Sterba wrote:
> 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.

Sounds good, thanks for the update. If there's anything else I can help 
with, please let me know.