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

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

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@rs.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.

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;
 }