Date: Wed, 18 Oct 2006 09:13:19 -0600
From: Matthew Wilcox <matthew@wil.cx>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Al Viro <viro@ftp.linux.org.uk>, Alexey Dobriyan <adobriyan@gmail.com>,
       linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: dealing with excessive includes
Message-ID: <20061018151319.GQ22289@parisc-linux.org>
References: <20061017005025.GF29920@ftp.linux.org.uk> <Pine.LNX.4.64.0610161847210.3962@g5.osdl.org> <20061017043726.GG29920@ftp.linux.org.uk> <Pine.LNX.4.64.0610170821580.3962@g5.osdl.org> <20061018044054.GH29920@ftp.linux.org.uk> <20061018091944.GA5343@martell.zuzino.mipt.ru> <20061018093126.GM29920@ftp.linux.org.uk> <Pine.LNX.4.64.0610180759070.3962@g5.osdl.org>
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On Wed, Oct 18, 2006 at 08:04:24AM -0700, Linus Torvalds wrote:
> On Wed, 18 Oct 2006, Al Viro wrote:
> >
> > +#define lock_super(x) do {		\
> > +	struct super_block *sb = x;	\
> > +	get_fs_excl();			\
> > +	mutex_lock(&sb->s_lock);	\
> > +} while(0)
> 
> Don't do this. The "x" passed in may be "sb", and then you end up with 
> bogus code.

For this one, I see a third way:

#define lock_super(sb) do {		\
	get_fs_excl();			\
	mutex_lock(&(sb)->s_lock);	\
} while (0)

It does have the disadvantage that you can pass *anything* that has
an s_lock field in ... but I don't think that's a very likely thing
to happen.

Or you could use _sb as the local variable, since it's a reserved
identifier.
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