linux-ext4 - Re: [PATCH] ext4: remove unnecessary operation in ext4_mb_normalize_group

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Message-ID: <20100405124814.GP18524@thunk.org>
Date:	Mon, 5 Apr 2010 08:48:14 -0400
From:	tytso@....edu
To:	jing zhang <zj.barak@...il.com>
Cc:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	Andreas Dilger <adilger@....com>,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Subject: Re: [PATCH] ext4: remove unnecessary operation in
 ext4_mb_normalize_group_request()

This patch has been marked as rejected in patchwork.

-- Ted

On Fri, Mar 26, 2010 at 10:37:49PM +0800, jing zhang wrote:
> 2010/3/26, Aneesh Kumar K. V <aneesh.kumar@...ux.vnet.ibm.com>:
> > On Fri, 26 Mar 2010 21:44:33 +0800, jing zhang <zj.barak@...il.com> wrote:
> >> 2010/3/26, Aneesh Kumar K. V <aneesh.kumar@...ux.vnet.ibm.com>:
> >> > On Thu, 25 Mar 2010 22:54:21 +0800, jing zhang <zj.barak@...il.com>
> >> > wrote:
> >> >> From: Jing Zhang <zj.barak@...il.com>
> >> >>
> >> >> Date: Wed Mar 25  22:55:04   2010
> >> >>
> >> >> Checking bug seems not at right place, and the function itself should
> >> >> be inlined.
> >> >>
> >> >> Cc: Theodore Ts'o <tytso@....edu>
> >> >> Cc: Andreas Dilger <adilger@....com>
> >> >> Cc: Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
> >> >> Cc: "Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
> >> >> Signed-off-by: Jing Zhang <zj.barak@...il.com>
> >> >>
> >> >> ---
> >> >>
> >> >> --- linux-2.6.32/fs/ext4/mballoc.c	2009-12-03 11:51:22.000000000 +0800
> >> >> +++ ext4_mm_leak/mballoc-10.c	2010-03-25 22:44:00.000000000 +0800
> >> >> @@ -2786,9 +2786,7 @@ out_err:
> >> >>  static void ext4_mb_normalize_group_request(struct
> >> >> ext4_allocation_context *ac)
> >> >>  {
> >> >>  	struct super_block *sb = ac->ac_sb;
> >> >> -	struct ext4_locality_group *lg = ac->ac_lg;
> >> >>
> >> >> -	BUG_ON(lg == NULL);
> >> >>  	if (EXT4_SB(sb)->s_stripe)
> >> >>  		ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_stripe;
> >> >>  	else
> >> >
> >> > That BUG_ON is to ensure that the allocation context is actually having
> >> > a locality group which is needed for group allocation request.
> >> >
> >> > -aneesh
> >> >
> >>
> >> Please check
> >> 1, the 3 lines at the end of ext4_mb_group_or_file()
> >> 2, the function name of this patch
> >>
> >
> > What i wanted to mention was the BUG_ON is there to ensure that we don't
> > call ext4_mb_normalize_group_request on non group enabled allocation
> > context by programming mistake. Doing that would cause ac_g_ex.fe_len
> > to change. So that BUG_ON is there to capture a programming error.
> >
> > -aneesh
> >
> 
> Thank you, Aneesh, for good explanation in patience.
> 
> Again, good weekend.
> 
> Still in work?
> 
>         - zj
> --
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