linux-ext4 - Re: there is a BUG in disk full case in inlinedata feature.

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Date:	Thu, 29 Aug 2013 23:15:44 +0800
From:	Boxi Liu <boxi10liu@...il.com>
To:	Tao Ma <tm@....ma>
Cc:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	Robin Dong <sanbai@...bao.com>, Theodore Tso <tytso@....edu>,
	"lewis.liulei" <lewis.liulei@...wei.com>
Subject: Re: there is a BUG in disk full case in inlinedata feature.

diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index c0fd1a1..f806f27 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -528,6 +528,7 @@ static int
ext4_convert_inline_data_to_extent(struct address_space *mapping,
  struct page *page = NULL;
  unsigned from, to;
  struct ext4_iloc iloc;
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);

  if (!ext4_has_inline_data(inode)) {
  /*
@@ -540,6 +541,9 @@ static int
ext4_convert_inline_data_to_extent(struct address_space *mapping,

  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;

2013/8/28 Tao Ma <tm@....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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