linux-ext4 - Re: [PATCH 2.6.33.y 14/40] ext4: Fix possible lost inode write in no journal mode

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Date:	Fri, 28 Sep 2012 11:08:41 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	Curt Wohlgemuth <curtw@...gle.com>
Cc:	stable@...r.kernel.org,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 2.6.33.y 14/40] ext4: Fix possible lost inode write in no
 journal mode

Hi Curt,

In journal mode, IMHO the case you described also happens. Could you
shed light on journal mode case?

Thanks,
Yongqiang.

On Tue, Jun 1, 2010 at 8:03 PM, Theodore Ts'o <tytso@....edu> wrote:
> From: Curt Wohlgemuth <curtw@...gle.com>
>
> commit 8b472d739b2ddd8ab7fb278874f696cd95b25a5e upstream (as of v2.6.34-rc6)
>
> In the no-journal case, ext4_write_inode() will fetch the bh and call
> sync_dirty_buffer() on it.  However, if the bh has already been
> written and the bh reclaimed for some other purpose, AND if the inode
> is the only one in the inode table block in use, then
> ext4_get_inode_loc() will not read the inode table block from disk,
> but as an optimization, fill the block with zero's assuming that its
> caller will copy in the on-disk version of the inode.  This is not
> done by ext4_write_inode(), so the contents of the inode can simply
> get lost.  The fix is to use __ext4_get_inode_loc() with in_mem set to
> 0, instead of ext4_get_inode_loc().  Long term the API needs to be
> fixed so it's obvious why latter is not safe.
>
> Addresses-Google-Bug: #2526446
>
> Signed-off-by: Curt Wohlgemuth <curtw@...gle.com>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
>  fs/ext4/inode.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index ff04c74..28152f8 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5204,7 +5204,7 @@ int ext4_write_inode(struct inode *inode, int wait)
>         } else {
>                 struct ext4_iloc iloc;
>
> -               err = ext4_get_inode_loc(inode, &iloc);
> +               err = __ext4_get_inode_loc(inode, &iloc, 0);
>                 if (err)
>                         return err;
>                 if (wait)
> --
> 1.6.6.1.1.g974db.dirty
>
> --
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-- 
Best Wishes
Yongqiang Yang
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