linux-ext4 - Re: [PATCH 1/1] Null Pointer when make_indexed

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Date:	Mon, 9 May 2011 13:36:32 +0200
From:	Jan Kara <jack@...e.cz>
To:	Yongqiang Yang <xiaoqiangnk@...il.com>
Cc:	Jan Kara <jack@...e.cz>,
	Allison Henderson <achender@...ux.vnet.ibm.com>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 1/1] Null Pointer when make_indexed_dir returns -ENOSPC

On Mon 09-05-11 19:33:19, Yongqiang Yang wrote:
> On Mon, May 9, 2011 at 7:30 PM, Jan Kara <jack@...e.cz> wrote:
> > On Mon 09-05-11 19:18:37, Yongqiang Yang wrote:
> >> On Mon, May 9, 2011 at 7:03 PM, Jan Kara <jack@...e.cz> wrote:
> >> > On Sat 07-05-11 16:54:27, Allison Henderson wrote:
> >> >> Fix for a null pointer bug found while running punch hole tests
> >> >>
> >> >> Signed-off-by: Allison Henderson <achender@...ibm.com>
> >> >> ---
> >> >> :100644 100644 3c7a06e... 3302a6c... M        fs/ext4/namei.c
> >> >>  fs/ext4/namei.c |    3 ++-
> >> >>  1 files changed, 2 insertions(+), 1 deletions(-)
> >> >>
> >> >> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> >> >> index 3c7a06e..3302a6c 100644
> >> >> --- a/fs/ext4/namei.c
> >> >> +++ b/fs/ext4/namei.c
> >> >> @@ -1422,7 +1422,8 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
> >> >>                */
> >> >>               ext4_mark_inode_dirty(handle, dir);
> >> >>               ext4_handle_dirty_metadata(handle, dir, frame->bh);
> >> >> -             ext4_handle_dirty_metadata(handle, dir, bh);
> >> >> +             if (bh)
> >> >> +                     ext4_handle_dirty_metadata(handle, dir, bh);
> >> >  I'm puzzled - bh here is bh2 from the beginning of the function and we
> >> > check it for being NULL after we ext4_append() it. So how can this happen?
> >> do_split() encounters a journal error and set bh to NULL before returning.
> > Ah, I see. But then you just reintroduced the bug I was trying to fix. So
> > either do_split() has to do the marking of buffer dirty, or we have to do
> > it before calllig do_split(), or do_split() has to be changed and not
> > release passed buffer (and the two callers have to do it - which they seem
> > to do anyway). I don't mind either way but your fix is wrong.
> The fix is made by Allison not me, I think Allison will have a look at
> the thread.
  Right, sorry. I was addressing Allison, not you of course ;).

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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