On Sat, Feb 13, 2021 at 12:36:02AM +0100, Michał Mirosław wrote: > 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.
I like the idea of storing numbers and simply checking them. I use it in v2 - though probably in a different form, and I will most likely move the whole logic around checking device types to separate functions, to not bloat btrfs_open_one_device() and the others too much.
