linux-kernel - RE: [f2fs-dev] [PATCH] f2fs: avoid to use a NULL point in destroy_segment

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Date:	Wed, 06 Nov 2013 13:10:58 +0800
From:	Chao Yu <chao2.yu@...sung.com>
To:	'Gu Zheng' <guz.fnst@...fujitsu.com>
Cc:	'???' <jaegeuk.kim@...sung.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	'谭姝' <shu.tan@...sung.com>
Subject: RE: [f2fs-dev] [PATCH] f2fs: avoid to use a NULL point in
 destroy_segment_manager

Hi Gu,

> -----Original Message-----
> From: Gu Zheng [mailto:guz.fnst@...fujitsu.com]
> Sent: Wednesday, November 06, 2013 11:41 AM
> To: Chao Yu
> Cc: ???; linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org; linux-f2fs-devel@...ts.sourceforge.net; 谭姝
> Subject: Re: [f2fs-dev] [PATCH] f2fs: avoid to use a NULL point in destroy_segment_manager
> 
> On 11/06/2013 09:12 AM, Chao Yu wrote:
> 
> > A NULL point should avoid to be used in destroy_segment_manager after allocating memory fail for f2fs_sm_info.
> 
> Though without this patch it still can work well, because if it failed
> to allocate f2fs_sm_info, the sit_info, free_info... all were NULL, and
> the destory path(e.g. destroy_dirty_segmap) can deal with them well.

I think it could not work well. Without this patch we may got a segment 
fault in DIRTY_I(sbi) at the following code if it failed to allocate 
f2fs_sm_info memory(sbi->sm_info). Right?

static void destroy_dirty_segmap(struct f2fs_sb_info *sbi)
{
	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);

> IMO, this patch is still a good catch.
> 
> Regards,
> Gu
> 
> >
> > Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> > ---
> >  fs/f2fs/segment.c |    2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 3d4d5fc..ff363e6
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1744,6 +1744,8 @@ static void destroy_sit_info(struct f2fs_sb_info *sbi)
> >  void destroy_segment_manager(struct f2fs_sb_info *sbi)
> >  {
> >  	struct f2fs_sm_info *sm_info = SM_I(sbi);
> > +	if (!sm_info)
> > +		return;
> >  	destroy_dirty_segmap(sbi);
> >  	destroy_curseg(sbi);
> >  	destroy_free_segmap(sbi);


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