linux-kernel - Re: [PATCH] VFS: Sanity check mount flags passed to change_mnt

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Message-ID: <AANLkTik-uXDtvA9G7sr1becN235PMzFWmuD5t9Xu4yZX@mail.gmail.com>
Date:	Fri, 27 Aug 2010 13:51:06 -0400
From:	Bob Copeland <me@...copeland.com>
To:	Valerie Aurora <vaurora@...hat.com>
Cc:	Matthew Wilcox <matthew@....cx>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Karel Zak <kzak@...hat.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] VFS: Sanity check mount flags passed to change_mnt_propagation()

On Fri, Aug 27, 2010 at 1:43 PM, Valerie Aurora <vaurora@...hat.com> wrote:
> On Thu, Aug 26, 2010 at 07:14:36PM -0600, Matthew Wilcox wrote:
>> Hrm.  I think we can do this a bit more pithily.
>>
>>       /* Only one propagation flag should be set, and no others */
>>       if (hweight32(type) != 1 &&
>>           (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
>>               return 0;
>>
>> Too clever?
>
> I was hoping someone would go find the best bitop for me, thanks. :)
> hweight32() is an awkward name but the comment makes it clear.  I'm
> happy with either.
>
> Thanks for the help,

Didn't read surrounding code, but is that supposed to be '||'?

Otherwise the case where only a single non-propagation flag is
set no longer returns 0...

-- 
Bob Copeland %% www.bobcopeland.com
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