linux-ext4 - Re: [PATCH] e2fsprogs: remove misleading argument from ext2fs_bg_flags

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Message-ID: <4A9F313E.8030605@redhat.com>
Date:	Wed, 02 Sep 2009 22:00:14 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Theodore Tso <tytso@....edu>
CC:	Andreas Dilger <adilger@....com>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] e2fsprogs: remove misleading argument from	ext2fs_bg_flags_clear

Theodore Tso wrote:
> On Wed, Sep 02, 2009 at 05:28:11PM -0600, Andreas Dilger wrote:
>> On Sep 02, 2009  16:43 -0500, Eric Sandeen wrote:
>>> ext2fs_bg_flags_clear shouldn't take an unused bg_flags argument
>>> if its purpose is to clear -all- flags.  That just makes people
>>> like me call it for the wrong purpose ;)
>> I'd pointed this out when the code was originally submitted.
>> That said, I'd prefer a function which allows clearing
>> individual flags, rather than all of them.  It is possible to
>> call it with ~0 to clear all of the flags.

ext2fs_bg_flag_clear(fs, group, flag) does just that...

TBH "ext2fs_bg_clear_flags(fs, group, ~0)" seems a bit tortured to me.

> Agreed; if we want to have a function which clears all of the flags,
> it should be named something like ext2fs_bg_flags_zap(), or some such.
> It would be confusing for ext2fs_bg_flags_clear() and
> ext2fs_bg_flags_set() not to be symmetric.
> 
> 						- Ted

But they are symmetric; just a bit odd in usage, esp. since the argument 
is ignored.

Ok should have looked closer; we have these which overwrite bg_flags:

void ext2fs_bg_flags_set(ext2_filsys fs, dgrp_t group, __u16 bg_flags);
void ext2fs_bg_flags_clear(ext2_filsys fs, dgrp_t group,__u16 bg_flags);

(_set sets exactly bg_flags; _clear clears all and ignores bg_flags)

and these, which can twiddle individual bits in bg_flags:

void ext2fs_bg_flag_set(ext2_filsys fs, dgrp_t group, __u16 bg_flag);
void ext2fs_bg_flag_clear(ext2_filsys fs, dgrp_t group, __u16 bg_flag);

hrmph.  Ok, not the most obvious.  I still don't think that an unused 
variable to "ext2fs_bg_flags_clear" is helpful, regardless of the name.

Oh, and ext2fs_bg_flags_set is unused it seems.

What about perhaps just these 3:

ext2fs_bg_flags_zero(fs, group) /* zeros bg_flags */

ext2fs_bg_flags_set(fs, group, flags) /* adds flags to bg_flags */
ext2fs_bg_flags_clear(fs, group, flags) /* clears flags in bg_flags */

and remove the original ext2fs_bg_flags_set / ext2fs_bg_flags_clear.

-Eric

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