On Wed, Dec 05, 2018 at 02:43:03PM +0200, Nikolay Borisov wrote:
> One question below though .
>
> > +++ b/fs/btrfs/super.c
> > @@ -739,6 +741,17 @@ int btrfs_parse_options(struct btrfs_fs_info *info,
> > char *options,
> > case Opt_user_subvol_rm_allowed:
> > btrfs_set_opt(info->mount_opt, USER_SUBVOL_RM_ALLOWED);
> > break;
> > +#ifdef CONFIG_FS_DAX
> > + case Opt_dax:
> > + if (btrfs_super_num_devices(info->super_copy) > 1) {
> > + btrfs_info(info,
> > + "dax not supported for multi-device
> > btrfs partition\n");
>
> What prevents supporting dax for multiple devices so long as all devices
> are dax?
As I mentioned in a separate mail, most profiles are either redundant
(RAID0), require hardware support (RAID1, DUP) or are impossible (RAID5,
RAID6).
But, "single" profile multi-device would be useful and actually provide
something other dax-supporting filesystems don't have: combining multiple
devices into one logical piece.
On the other hand, DUP profiles need to be banned. In particular, the
filesystem you mount might have existing DUP block groups.
Meow!
--
⢀⣴⠾⠻⢶⣦⠀
⣾⠁⢠⠒⠀⣿⡁ Ivan was a worldly man: born in St. Petersburg, raised in
⢿⡄⠘⠷⠚⠋⠀ Petrograd, lived most of his life in Leningrad, then returned
⠈⠳⣄⠀⠀⠀⠀ to the city of his birth to die.
