linux-kernel - Re: [PATCH v8 4/3] cgroups: use flex_array in attach

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Message-ID: <20110322051553.GB11447@ghc17.ghc.andrew.cmu.edu>
Date:	Tue, 22 Mar 2011 01:15:53 -0400
From:	Ben Blum <bblum@...rew.cmu.edu>
To:	Paul Menage <menage@...gle.com>
Cc:	Ben Blum <bblum@...rew.cmu.edu>, linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, akpm@...ux-foundation.org,
	ebiederm@...ssion.com, lizf@...fujitsu.com, matthltc@...ibm.com,
	oleg@...hat.com, David Rientjes <rientjes@...gle.com>,
	Miao Xie <miaox@...fujitsu.com>
Subject: Re: [PATCH v8 4/3] cgroups: use flex_array in attach_proc

On Thu, Mar 03, 2011 at 09:48:09AM -0800, Paul Menage wrote:
> On Wed, Feb 16, 2011 at 11:22 AM, Ben Blum <bblum@...rew.cmu.edu> wrote:
> > Convert cgroup_attach_proc to use flex_array.
> >
> > From: Ben Blum <bblum@...rew.cmu.edu>
> >
> > The cgroup_attach_proc implementation requires a pre-allocated array to store
> > task pointers to atomically move a thread-group, but asking for a monolithic
> > array with kmalloc() may be unreliable for very large groups. Using flex_array
> > provides the same functionality with less risk of failure.
> >
> > This is a post-patch for cgroup-procs-write.patch.
> >
> > Signed-off-by: Ben Blum <bblum@...rew.cmu.edu>
> 
> Reviewed-by: Paul Menage <menage@...gle.com>
> 
> Looks fine from a correctness point of view, but I'd be inclined to
> reduce the verbosity - rather than
> 
> tsk = flex_array_get_ptr(group, i);
> BUG_ON(tsk == NULL);
> retval = ss->can_attach_task(cgrp, tsk);
> 
> I'd just have
> 
> retval = ss->can_attach_task(cgrp, flex_array_get_ptr(group, i));
> 
> I don't think you need to be so defensive about flex_array's behaviour.
> 
> Paul
> 

hmm, in this case that change would make it cross 80 columns (and I
liked consistency). ;)

I've removed the BUG_ONs, though.

-- Ben
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