testing result of loop-aio patchset on ext3
From: Rui Xiang
Date: Mon Jul 14 2014 - 05:35:04 EST
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
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:
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).
Free inodes count wrong (640837, counted=640835).
raw_image: ********** WARNING: Filesystem still has errors **********
raw_image: 11/640848 files (0.0% non-contiguous), 78652/2560000 blocks
With a specific script, I can almost 100% reproduce this issue.
And it seems the corruption can only happen when reboot happens at the
time loop is calling vfs_fsync().
Do you have any idea why the loop-aio patchset doesn't help?
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