linux-ext4 - Re: testing result of loop-aio patchset on ext3

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Date:	Wed, 16 Jul 2014 11:54:24 +0800
From:	Rui Xiang <rui.xiang@...wei.com>
To:	Lukáš Czerner <lczerner@...hat.com>
CC:	Dave Kleikamp <dave.kleikamp@...cle.com>,
	<linux-ext4@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Li Zefan <lizefan@...wei.com>
Subject: Re: testing result of loop-aio patchset on ext3

On 2014/7/14 17:51, Lukáš Czerner wrote:
> On Mon, 14 Jul 2014, Rui Xiang wrote:
> 
>> Date: Mon, 14 Jul 2014 17:34:38 +0800
>> From: Rui Xiang <rui.xiang@...wei.com>
>> To: Dave Kleikamp <dave.kleikamp@...cle.com>, linux-ext4@...r.kernel.org
>> Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
>>     Li Zefan <lizefan@...wei.com>
>> Subject: testing result of loop-aio patchset on ext3
>>
>> Hi Dave,
>>
>> We export a container image file as a block device via loop device, but we
>> found it's very easy that the container rootfs gets corrupted due to power
>> loss.
>>
>> Your early version of loop-aio patchset said the patchset can make loop
>> mounted filesystems recoverable(lkml.org/lkml/2012/3/30/317), but we found
>> it doesn't help.
>>
>> Both the guest fs and host fs are ext3.
>>
>> The loop-aio patchset is from:
>> git://github.com/kleikamp/linux-shaggy.git aio_loop
>>
>> Steps:
>> 1. dd a 10G image, mkfs.ext3,
>>   # dd if=/dev/zero of=./raw_image bs=1M count=10000
>>   # echo y | mkfs.ext3 raw_image
>>
>> 2. losetup a loop device, mount at ./test_dir
>>   # losetup /dev/loop1 raw_image
>>   # mount /dev/loop1 ./test_dir
>>
>> 3. copy fs_mark into test_dir and run
>>   # ./fs_mark -d ./tmp/ -s 102400000 -n 80
>>
>> 4. during runing fs_mark, make systerm reboot indirectly.
>>   # echo b > /proc/sysrq-trigger
>>
>> After systerm booted up, sometimes fsck reported raw_image fs has been damaged.
>>
>> # fsck.ext3 -n raw_image
>> e2fsck 1.41.9 (22-Aug-2009)
>> Warning: skipping journal recovery because doing a read-only filesystem check.
>> raw_image contains a file system with errors, check forced.
>> Pass 1: Checking inodes, blocks, and sizes
>> Pass 2: Checking directory structure
>> Pass 3: Checking directory connectivity
>> Pass 4: Checking reference counts
>> Pass 5: Checking group summary information
>> Free blocks count wrong (2481348, counted=2480577).
>> Fix? no
>> Free inodes count wrong (640837, counted=640835).
>> Fix? no
>> raw_image: ********** WARNING: Filesystem still has errors **********
>> raw_image: 11/640848 files (0.0% non-contiguous), 78652/2560000 blocks
> 
> It's not damaged, this is expected result if you're using old
> e2fsprogs which still treats this as an error.
> 
> It's not an error because we only update superblock summary at
> unmount time so with unclean shutdown it's likely that it does not
> match the reality, but e2fsck can and will easily fix that for you.
> 
> Please try e2fsprogs v1.42.3 or newer.
> 

Hi Lukas,

I updated e2fsprogs to v1.42.3, and user the newer fsck.ext3 to check raw_image.
Exactly, the result seemed normal.

Then, I continue my previous test. And after testing 35 times, "fsck -n" reported image fs
had been damaged, too.

 # fsck.ext3 -n image1
e2fsck 1.42.3.wc1 (28-May-2012)
Warning: skipping journal recovery because doing a read-only filesystem check.
image1 has been mounted 36 times without being checked, check forced.
Pass 1: Checking inodes, blocks, and sizes
Inode 16407, i_size is 597447, should be 602112.  Fix? no
Inode 16407, i_blocks is 1176, should be 1184.  Fix? no
Inode 409941, i_blocks is 200208, should be 112.  Fix? no
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
Block bitmap differences:  -1506836 -1506843 -(1506859--1506860) -(1660941--1661964) -(1661966--1671167) -(1671688--1686473)
Fix? no
Free blocks count wrong for group #2 (31558, counted=31556).
Fix? no
Free blocks count wrong for group #43 (15871, counted=15867).
Fix? no
Free blocks count wrong (2204041, counted=2204035).
Fix? no
image1: ********** WARNING: Filesystem still has errors **********
image1: 13008/655360 files (0.3% non-contiguous), 417399/2621440 blocks

I backup the image to image_bk, and then mount the image to a dir, and cat all files in the image.
Steps:
# dd if=image1 of=image_bk
# mount image1 err_dir
# find -name '*' -exec cat > /dev/null {} \;

There are no issues during catting, and no err in dmesg too.

*But when I umount the image1 from err_dir, The fsck result didn't show any fs corruption info.

I mount image_bk to err_dir and umount it with no operation directly. The result is same to iamge1.

*So, is fs in the image as a block device via loop device damaged really, or does it have some others issues? 
Could you give me some opinions?

Thanks.

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