Re: [PATCH] btrfs: drop the nossd flag when remounting with -o ssd

[Hans van Kranenburg <hans.van.kranenburg@mendix.com>]

On 03/31/2017 05:19 PM, Adam Borowski wrote:
> The opposite case was already handled right in the very next switch entry.
> 
> Reported-by: Hans van Kranenburg <hans.van.kranenburg@mendix.com>
> Signed-off-by: Adam Borowski <kilobyte@angband.pl>
> ---
> Not sure if setting NOSSD should also disable SSD_SPREAD, there's currently
> no way to disable that option once set.
> 
>  fs/btrfs/super.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 06bd9b332e18..7342399951ad 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -549,11 +549,13 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
>  		case Opt_ssd:
>  			btrfs_set_and_info(info, SSD,
>  					   "use ssd allocation scheme");
> +			btrfs_clear_opt(info->mount_opt, NOSSD);
>  			break;
>  		case Opt_ssd_spread:
>  			btrfs_set_and_info(info, SSD_SPREAD,
>  					   "use spread ssd allocation scheme");
>  			btrfs_set_opt(info->mount_opt, SSD);
> +			btrfs_clear_opt(info->mount_opt, NOSSD);
>  			break;
>  		case Opt_nossd:
>  			btrfs_set_and_info(info, NOSSD,

How did you test this?

This was also my first thought, but here's a weird thing:

-# mount -o nossd /dev/sdx /mnt/btrfs/

BTRFS info (device sdx): not using ssd allocation scheme

-# mount -o remount,ssd /mnt/btrfs/

BTRFS info (device sdx): use ssd allocation scheme

-# mount -o remount,nossd /mnt/btrfs/

BTRFS info (device sdx): use ssd allocation scheme

That means that the case Opt_nossd: is never reached when doing this?

And... what should be the result of doing:
-# mount -o remount,nossd,ssd /mnt/btrfs/

I guess it should be that the last one in the sequence wins?

The fact that nossd,ssd,ssd_spread are different options complicates the
whole thing, compared to e.g. autodefrag, noautodefrag.

-- 
Hans van Kranenburg