linux-ext4 - Re: [PATCH] ext4:Fix a bug in ext4_ext_fiemap

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Date:	Thu, 24 Feb 2011 10:36:43 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Yongqiang Yang <xiaoqiangnk@...il.com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4:Fix a bug in ext4_ext_fiemap_cb().

On 02/23/2011 06:33 PM, Yongqiang Yang wrote:
> On Thu, Feb 24, 2011 at 12:41 AM, Eric Sandeen <sandeen@...hat.com> wrote:
>> On 2/23/11 9:59 AM, Yongqiang Yang wrote:

...

>>> @@ -3830,7 +3845,8 @@ static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path,
>>>        *
>>>        * XXX this might miss a single-block extent at EXT_MAX_BLOCK
>>>        */
>>> -     if (ext4_ext_next_allocated_block(path) == EXT_MAX_BLOCK ||
>>> +     end = ext4_ext_next_allocated_block(path);
>>
>> I think this will fall down if you have:
>>
>> [ HOLE ][ DELALLOC ][ HOLE ][ ALLOCATED ] won't it?
>>
>> i.e. your "end" will be the first block of "allocated" right?
> Yes, but it neglect nothing.  If we want to deal his model, we need to
> lookup dirty pages in specified range.
> 

I think it's clearly a bug to return a delalloc range when in fact it's
a hole...

> We use pagevec_lookup_tag() instead of find_get_page() and check
> BH_Delay of contiguous pages. Then, we can deal this model.

Yes, that's how I was going to go about it before you jumped right in,
thanks! :)

-Eric
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