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

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Message-ID: <493795BA.4010507@rs.jp.nec.com>
Date:	Thu, 04 Dec 2008 17:32:58 +0900
From:	Akira Fujita <a-fujita@...jp.nec.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
CC:	Theodore Tso <tytso@....edu>, Li Zefan <lizf@...fujitsu.com>,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH]ext4: fix s_dirty_blocks_counter if block allocation	failed
 with nodelalloc


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>

> 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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