Re: there is a BUG in disk full case in inlinedata feature.

[Tao Ma <tm@tao.ma>]

Hi Boxi,
On 10/22/2013 12:22 AM, Boxi Liu wrote:
> hi,
> I make the format patch about the inline_data patch .
> Is there anything incomplete？
Please do as what Darrick has said. You need to run
scripts/checkpatch.pl to check these format issues.

btw, as I have already acked your change, you can add this line above
your Signed-off-by.
Acked-by: Tao Ma <boyu.mt@taobao.com>

Thanks,
Tao
> 
> Thanks
> boxi
> 
> 2013/8/28 Tao Ma <tm@tao.ma>:
>> Hi Boxi,
>>         Thanks for the detailed explanation and the bug fix. It looks good to me.
>>         So would you mind send out a formal patch?
>>
>> Thanks,
>> Tao
>> On 08/28/2013 01:09 AM, Boxi Liu wrote:
>>> there is a BUG in EXT4 inlinedata feature when the disk is full(0B).
>>> tast case:
>>>     step1: use the dd to make the disk full,has 0B remained.
>>>     step2: touch a inlinedata file
>>>            echo -n "123456" >> test.txt
>>>     step3: make the inlinedata file test.txt convert to extent block.
>>>            echo -n
>>> "123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890">>test.txt
>>> the step3 will write failed.and print the BUG Backtrace:
>>> page:c1963bc0 count:-1 mapcount:0 mapping: (null) index:0x0
>>> page flags:0x40000000()
>>> Backtrace:
>>> [<c004e180>] (dump_backtrace + 0x0/0x12c) from [<c07724ac>]
>>> (dump_stack +0x18/0x1c)
>>> r6:c0043a84  r5:c0bb688  r4:c1963bc0 r3:00000000
>>> [<c0772494>] (dump_stack + 0x0/0x1c) from [<c00f6dd4>] (bad_page + 0xbc/0x13c)
>>> [<c00fbd18>] (bad_page + 0x0/0x13c) from [<c00f74b80>]
>>> (get_page_from_freelist + 0x4cc/0xb6c)
>>> r7:c1963bd8 r6:c0043194 r5:c1963bc0 r4:00000001
>>> [<c00f6fec>] (get_page_from_freelist +0x0/0xb6c) from [<c00f8148>]
>>> (__alloc_pages_nodemask + 0x144/0x820)
>>> [<c00f8004>] (__alloc_pages_nodemask +0x0/0x820) from [<c0115250>]
>>> (handle_pte_fault + 0x574/0x758)
>>> [<c0114cdc>] (handle_pte_fault + 0x0/0x758) from [<c0115500>]
>>> (handle_mm_fault + 0xcc/0x110)
>>> [<c0115434>] (handel_mm_fault + 0x0/0x110) from [<c00521a8>]
>>> (do_page_fault + 0x16c/0x1f4)
>>> [<c005203c>] (do_page_fault + 0x0/0x1f4) from [<c00440d0>]
>>> (do_DataAbort + 0x40/0xac)
>>> [<c0044090>] (do_DataAbort + 0x0/0xac) from [<c004a064>]
>>> (ret_from_exception + 0x0/0x10)
>>>
>>> And when the system reboot , the step2 data "123456" will alse lost.
>>> You can cat the test.txt,but there is no data in the file.
>>> the reason is when the inlinedata convert to extent in the limit case,
>>> the inlinedata read to the page,then destory the inlinedata,next step
>>> is to __block_write_begin,but it can't get block,return -ENOSPC. so
>>> the data lost.
>>>
>>> there is a patch may fix the bug:
>>> in inline.c ext4_convert_inline_data_to_extent
>>>
>>>          needed_blocks = ext4_writepage_trans_blocks(inode);
>>>
>>> +        if(EXT4_C2B(sbi,percpu_counter_read_positive(&sbi->s_freeclusters_counter))
>>> < needed_blocks)
>>> +               return -ENOSPC;
>>> +
>>>          ret = ext4_get_inode_loc(inode, &iloc);
>>>          if (ret)
>>>                  return ret;
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>>

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