linux-ext4 - Re: [PATCH v9 2/9] ext4: add fast_commit feature and handling for extended mount options

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Message-ID: <20201009175836.GM235506@mit.edu>
Date:   Fri, 9 Oct 2020 13:58:36 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH v9 2/9] ext4: add fast_commit feature and handling for
 extended mount options

On Fri, Sep 18, 2020 at 05:54:44PM -0700, Harshad Shirwadkar wrote:
> We are running out of mount option bits. Add handling for using
> s_mount_opt2. Add ext4 and jbd2 fast commit feature flag and also add
> ability to turn on / off the fast commit feature in Ext4.

Shouldn't that read "...ability to turn off the fast commit feature via a
mount option"?

> @@ -2207,10 +2211,17 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
>  			WARN_ON(1);
>  			return -1;
>  		}
> -		if (arg != 0)
> -			sbi->s_mount_opt |= m->mount_opt;
> -		else
> -			sbi->s_mount_opt &= ~m->mount_opt;
> +		if (m->flags & MOPT_2) {
> +			if (arg != 0)
> +				sbi->s_mount_opt2 |= m->mount_opt;
> +			else
> +				sbi->s_mount_opt2 &= ~m->mount_opt;
> +		} else {
> +			if (arg != 0)
> +				sbi->s_mount_opt |= m->mount_opt;
> +			else
> +				sbi->s_mount_opt &= ~m->mount_opt;
> +		}
>  	}
>  	return 1;
>  }

This requires a matching change in _ext4_show_options(), so that the
MOPT_2 options are properly displayed in /proc/mounts.

						- Ted