linux-ext4 - Re: [PATCH 02/17] ext4: Add fs parameter description

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Date:   Tue, 17 Dec 2019 00:44:19 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Lukas Czerner <lczerner@...hat.com>
Cc:     linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
        David Howells <dhowells@...hat.com>
Subject: Re: [PATCH 02/17] ext4: Add fs parameter description

On Wed, Nov 06, 2019 at 11:14:42AM +0100, Lukas Czerner wrote:
> +	fsparam_string_empty
> +			("usrjquota",		Opt_usrjquota),
> +	fsparam_string_empty
> +			("grpjquota",		Opt_grpjquota),

Umm...  That makes ...,usrjquota,... equivalent to ...,usrjquota=,...
unless I'm misreading the series.  Different from mainline, right?

> +	fsparam_bool	("barrier",		Opt_barrier),
> +	fsparam_flag	("nobarrier",		Opt_nobarrier),

That's even more interesting.  Current mainline:
		barrier		OK, sets EXT4_MOUNT_BARRIER
		barrier=0	OK, sets EXT4_MOUNT_BARRIER
		barrier=42	OK, sets EXT4_MOUNT_BARRIER
		barrier=yes	error
		barrier=no	error
		nobarrier	OK, clears EXT4_MOUNT_BARRIER
Unless I'm misreading your series, you get
		barrier		error
		barrier=0	OK, sets EXT4_MOUNT_BARRIER
		barrier=42	error
		barrier=yes	OK, sets EXT4_MOUNT_BARRIER
		barrier=no	OK, sets EXT4_MOUNT_BARRIER
		nobarrier	OK, clears EXT4_MOUNT_BARRIER

Granted, mainline behaviour is... unintuitive, to put it mildly,
but the replacement is just as strange _and_ incompatible with the
existing one.

Am I missing something subtle there?