Re: [PATCH] btrfs: auto enable discard=async when possible

[Roman Mamedov <rm@romanrm.net>]

On Wed, 27 Jul 2022 17:01:58 +0200
David Sterba <dsterba@suse.com> wrote:

> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1503,6 +1503,7 @@ enum {
>  	BTRFS_MOUNT_DISCARD_ASYNC		= (1UL << 28),
>  	BTRFS_MOUNT_IGNOREBADROOTS		= (1UL << 29),
>  	BTRFS_MOUNT_IGNOREDATACSUMS		= (1UL << 30),
> +	BTRFS_MOUNT_NODISCARD			= (1UL << 31),
>  };
>  
>  #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 3fac429cf8a4..8f8e33219d4d 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3767,6 +3767,20 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
>  		btrfs_set_and_info(fs_info, SSD, "enabling ssd optimizations");
>  	}
>  
> +	/*
> +	 * For devices supporting discard turn on discard=async automatically,
> +	 * unless it's already set or disabled. This could be turned off by
> +	 * nodiscard for the same mount.
> +	 */
> +	if (!(btrfs_test_opt(fs_info, DISCARD_SYNC) ||
> +	      btrfs_test_opt(fs_info, DISCARD_ASYNC) ||
> +	      btrfs_test_opt(fs_info, NODISCARD)) &&
> +	    fs_info->fs_devices->discardable) {
> +		btrfs_set_and_info(fs_info, DISCARD_ASYNC,
> +				"auto enabling discard=async");
> +	      btrfs_clear_opt(fs_info->mount_opt, NODISCARD);

Spaces are used in the above line instead of a 2nd TAB.

Also I am probably clueless, but it seems the condition just checked that
NODISCARD was not set, so what is the purpose of also clearing it?

Thanks

-- 
With respect,
Roman