On Fri, Feb 12, 2021 at 06:26:41PM +0000, Michal Rostecki wrote:
> On Wed, Feb 10, 2021 at 05:08:05AM +0100, Michał Mirosław wrote:
> > On Tue, Feb 09, 2021 at 09:30:38PM +0100, Michal Rostecki wrote:
> > > From: Michal Rostecki <mroste...@suse.com>
> > >
> > > Add the btrfs_check_mixed() function which checks if the filesystem has
> > > the mixed type of devices (non-rotational and rotational). This
> > > information is going to be used in roundrobin raid1 read policy.a
> > [...]
> > > @@ -669,8 +699,12 @@ static int btrfs_open_one_device(struct
> > > btrfs_fs_devices *fs_devices,
> > > }
> > >
> > > q = bdev_get_queue(bdev);
> > > - if (!blk_queue_nonrot(q))
> > > + rotating = !blk_queue_nonrot(q);
> > > + device->rotating = rotating;
> > > + if (rotating)
> > > fs_devices->rotating = true;
> > > + if (!fs_devices->mixed)
> > > + fs_devices->mixed = btrfs_check_mixed(fs_devices, rotating);
> > [...]
> >
> > Since this is adding to a set, a faster way is:
> >
> > if (fs_devices->rotating != rotating)
> > fs_devices->mixed = true;
> >
> > The scan might be necessary on device removal, though.
> Actually, that's not going to work in case of appenging a rotational
> device when all previous devices are non-rotational.
[...]
> Inverting the order of those `if` checks would break the other
> permuitations which start with rotational disks.
But not if you would add:
if (adding first device)
fs_devices->rotating = rotating;
before the checks.
But them, there is a simpler way: count how many rotating vs non-rotating
devices there are while adding them. Like:
rotating ? ++n_rotating : ++n_fixed;
And then on remove you'd have it covered.
Best Regards
Michał Mirosław
