From: Mingming Cao <cmm@us.ibm.com>
Subject: Re: [PATCH] ext4: mballoc avoid use root reserved blocks for non
	root allocation
Date: Fri, 06 Jun 2008 11:59:24 -0700
Message-ID: <1212778764.22102.6.camel@localhost.localdomain>
References: <1212354413.4368.7.camel@localhost.localdomain>
	 <20080606023345.GH30272@mit.edu>
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Cc: linux-ext4@vger.kernel.org
To: Theodore Tso <tytso@MIT.EDU>
In-Reply-To: <20080606023345.GH30272@mit.edu>
Sender: linux-ext4-owner@vger.kernel.org

On Thu, 2008-06-05 at 22:33 -0400, Theodore Tso wrote:
> On Sun, Jun 01, 2008 at 02:06:53PM -0700, Mingming Cao wrote:
> > ext4: mballoc avoid use root reserved blocks for non root allocation
> > 
> > From: Mingming Cao <cmm@us.ibm.com>
> > 
> > mballoc allocation missed check for blocks reserved for root users. Add
> > ext4_has_free_blocks() check before allocation. Also modified
> > ext4_has_free_blocks() to support multiple block allocation request.
> 
> This was discovered by a Gentoo user who tried compiling on a UP system.....
> 
> > Index: linux-2.6.26-rc4/fs/ext4/balloc.c
> > ....
> > +	if (free_blocks - root_blocks < FBC_BATCH)
> > +		free_blocks =
> > +			percpu_counter_sum_positive(&sbi->s_freeblocks_counter);
> 
> 
> FBC_BATCH is only defined if CONFIG_SMP is defined.  I believe the
> simplest fix is surround the above if statement with an "#ifdef
> CONFIG_SMP", since on UP systems, the percpu counters are always
> exactly correct.
> 

Works for me. One up system the counter is always accurate.

FBC_BATCH is just some value to trigger sum up from per cpu counters to
get the accurate value, we don't need to do this for single UP.

Mingming
> 					- Ted