Re: [PATCH v2] btrfs: fix nossd and ssd_spread mount option regression

[Eric Sandeen <sandeen@redhat.com>]

On 7/1/14, 11:19 PM, Qu Wenruo wrote:
> From: Eric Sandeen <sandeen@redhat.com>
> 
> The commit
> 
> 0780253 btrfs: Cleanup the btrfs_parse_options for remount.
> 
> broke ssd options quite badly; it stopped making ssd_spread
> imply ssd, and it made "nossd" unsettable.
> 
> Put things back at least as well as they were before
> (though ssd mount option handling is still pretty odd:
> 
> Reported-by: Roman Mamedov <rm@romanrm.net>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> ---
> v2(By Qu):
>   Make nossd disable ssd and ssd_spread.
>   Add notes in Documentation/btrfs.txt

Ok, thanks for fixing up a little bit more.

But option handling is still strange even with your changes:

# mount -o ssd /dev/sdc3 /mnt/test; grep sdc3 /proc/mounts
/dev/sdc3 /mnt/test btrfs rw,seclabel,relatime,ssd,space_cache 0 0

# mount -o remount,nossd /dev/sdc3 /mnt/test; grep sdc3 /proc/mounts
/dev/sdc3 /mnt/test btrfs rw,seclabel,relatime,nossd,space_cache 0 0

# mount -o remount,ssd_spread /dev/sdc3 /mnt/test; grep sdc3 /proc/mounts
/dev/sdc3 /mnt/test btrfs rw,seclabel,relatime,nossd,ssd_spread,space_cache 0 0

# mount -o remount,ssd /dev/sdc3 /mnt/test; grep sdc3 /proc/mounts
/dev/sdc3 /mnt/test btrfs rw,seclabel,relatime,nossd,ssd_spread,space_cache 0 0

I'd rather just commit my first patch to fix the regression ASAP, and
fix the ssd option mess with a second patch which has received careful testing.

-Eric

> ---
>  Documentation/filesystems/btrfs.txt | 3 +++
>  fs/btrfs/super.c                    | 4 +++-
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt
> index d11cc2f..f7d0878 100644
> --- a/Documentation/filesystems/btrfs.txt
> +++ b/Documentation/filesystems/btrfs.txt
> @@ -201,6 +201,9 @@ Options with (*) are default options and will not show in the mount options.
>  	of unused space, and may perform better on low-end ssds.  ssd_spread
>  	implies ssd, enabling all other ssd heuristics as well.
>  
> +	Option nossd removes all ssd allocation heuristics, disabling
> +	ssd_spread or ssd mount option.
> +
>    subvol=<path>
>  	Mount subvolume at <path> rather than the root subvolume.  <path> is
>  	relative to the top level subvolume.
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 4662d92..cfe377a 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -522,10 +522,12 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
>  		case Opt_ssd_spread:
>  			btrfs_set_and_info(root, SSD_SPREAD,
>  					   "use spread ssd allocation scheme");
> +			btrfs_set_opt(info->mount_opt, SSD);
>  			break;
>  		case Opt_nossd:
> -			btrfs_clear_and_info(root, NOSSD,
> +			btrfs_set_and_info(root, NOSSD,
>  					     "not using ssd allocation scheme");
> +			btrfs_clear_opt(info->mount_opt, SSD_SPREAD);
>  			btrfs_clear_opt(info->mount_opt, SSD);
>  			break;
>  		case Opt_barrier:
>