linux-ext4 - Re: [PATCH]ext4: fix s_dirty_blocks_counter if block allocation failed with nodelalloc

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Date:	Thu, 04 Dec 2008 16:38:04 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Akira Fujita <a-fujita@...jp.nec.com>
CC:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Theodore Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH]ext4: fix s_dirty_blocks_counter if block allocation	failed
 with nodelalloc

Akira Fujita wrote:
> 
> Aneesh Kumar K.V wrote:
>> On Thu, Dec 04, 2008 at 10:27:25AM +0900, Akira Fujita wrote:
>>> Hi Aneesh,
>>> Aneesh Kumar K.V wrote:
>>>> On Mon, Dec 01, 2008 at 07:21:54PM +0900, Akira Fujita wrote:
>>>>> ext4: Fix s_dirty_blocks_counter if block allocation failed with
>>>>> nodelalloc
>>>>>
>>>>> From: Akira Fujita <a-fujita@...jp.nec.com>
>>>>>
>>>>> If block allocation failed after marking claimed blocks as dirty
>>>>> blocks
>>>>> with nodelalloc, we have to subtract these blocks from
>>>>> s_dirty_blocks_counter in error handling.
>>>>> Otherwise s_dirty_blocks_counter goes wrong so that
>>>>> filesystem's free blocks decreases incorrectly.
>>>> Why did the block allocation fail ? With delayed allocation ENOSPC
>>>> should not happen during block allocation. That would mean we did
>>>> something wrong in block reservation.
>>> My case was *nodelalloc* and FS was almost full.
>>> This problem occurs in multiple defrag running in short time.
>>> Usually defrag releases temporary inode's blocks with iput,
>>> then FS free blocks are recover but contiguous blocks do not recover
>>> until next journal commit.
>>> so we can not re-use contiguous blocks immediately.
>>> There are enough free blocks in FS so that
>>> ext4_claim_free_blocks marks claimed blocks as dirty,
>>> but ext4_regular_allocator can not find enough blocks,
>>> so mb_new_blocks returns ENOSPC without decreasing dirty blocks.
>>>
>> ok how about doing the check once in ext4_mb_new_blocks.
> 
> It works fine.  Thank you.
> Tested-by: Akira Fujita <a-fujita@...jp.nec.com>
> 

I'll test it when I'm free and have access to the test machine. :)

But not this week..

>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index bacc2f4..22d31c3 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -4550,7 +4550,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
>>      }
>>      if (ar->len == 0) {
>>          *errp = -EDQUOT;
>> -        return 0;
>> +        goto out3;
>>      }
>>      inquota = ar->len;
>>  
>> @@ -4623,6 +4623,13 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
>>  out1:
>>      if (ar->len < inquota)
>>          DQUOT_FREE_BLOCK(ar->inode, inquota - ar->len);
>> +out3:
>> +    if (!ar->len) {
>> +        if (!EXT4_I(ar->inode)->i_delalloc_reserved_flag)
>> +            /* release all the reserved blocks if non delalloc */
>> +            percpu_counter_sub(&sbi->s_dirtyblocks_counter,
>> +                        reserv_blks);
>> +    }
>>  
>>      return block;
>>  }
> 
> 
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