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

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Message-ID: <CAGBYx2Z8J8ktFCjx5Jr9PmBP2q1w_2Cz45gAen9gLXFqM7XZjw@mail.gmail.com>
Date:	Fri, 28 Sep 2012 11:21:16 +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

I got it!

Thanks,
Yongqiang.
On Fri, Sep 28, 2012 at 11:08 AM, Yongqiang Yang <xiaoqiangnk@...il.com> wrote:
> 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



-- 
Best Wishes
Yongqiang Yang
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