Date:   Wed, 14 Dec 2022 21:46:15 +0800
From:   Zhang Yi <yi.zhang@...weicloud.com>
To:     linux-ext4@...r.kernel.org
Cc:     tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz,
        yukuai3@...wei.com
Subject: Re: [PATCH v2 00/12] ext4: enhance simulate fail facility

Hello, is anybody have advice?

Thanks,
Yi.

On 2022/11/10 10:25, Zhang Yi wrote:
> Changes since v1:
>  - Fix format error in ext4_fault_ops_write().
> 
> Now we can test ext4's reliability by simulating fail facility introduced
> in commit 46f870d690fe ("ext4: simulate various I/O and checksum errors
> when reading metadata"), it can simulate checksum error or I/O error
> when reading metadata from disk. But it is functional limited, it cannot
> set failure times, probability, filters, etc. Fortunately, we already
> have common fault-injection frame in Linux, so above limitation could be
> easily supplied by using it in ext4. This patch set add ext4
> fault-injection facility to replace the old frame, supply some kinds of
> checksum error and I/O error, and also add group, inode, physical
> block and inode logical block filters. After this patch set, we could
> inject failure more precisly. The facility could be used to do fuzz
> stress test include random errors, and it also could be used to
> reprodece issues more conveniently.
> 
> Patch 1: add debugfs for preparing.
> Patch 2: introduce the fault-injection frame for ext4.
> Patch 3-11: add various kinds of faults and also do some cleanup.
> Patch 12: remove the old simulating facility.
> 
> It provides a debugfs interface in ext4/<disk>/fault_inject, besides the
> common config interfaces, we give 6 more.
>  - available_faults: present available faults we can inject.
>  - inject_faults: set faults, can set multiple at a time.
>  - inject_inode: set the inode filter, matches all inodes if not set.
>  - inject_group: set the block group filter, similar to inject_inode.
>  - inject_logical_block: set the logical block filter for one inode.
>  - inject_physical_block: set the physical block filter.
> 
> Current we add 20 available faults list below, include 8 kinds of
> metadata checksum error, 7 metadata I/O error and 5 journal error.
> After we have this facility, more other faults could be added easily
> in the future.
>  - group_desc_checksum
>  - inode_bitmap_checksum
>  - block_bitmap_checksum
>  - inode_checksum
>  - extent_block_checksum
>  - dir_block_checksum
>  - dir_index_block_checksum
>  - xattr_block_checksum
>  - inode_bitmap_eio
>  - block_bitmap_eio
>  - inode_eio
>  - extent_block_eio
>  - dir_block_eio
>  - xattr_block_eio
>  - symlink_block_eio
>  - journal_start
>  - journal_start_sb
>  - journal_get_create_access
>  - journal_get_write_access
>  - journal_dirty_metadata
> 
> For example: inject inode metadata checksum error on file 'foo'.
> 
> $ mkfs.ext4 -F /dev/pmem0
> $ mount /dev/pmem0 /mnt
> $ mkdir /mnt/dir
> $ touch /mnt/dir/foo
> $ ls -i /mnt/dir/foo
>   262146 /mnt/foo
> 
> $ echo 100 > /sys/kernel/debug/ext4/pmem0/fault_inject/probability
> $ echo 1 > /sys/kernel/debug/ext4/pmem0/fault_inject/times
> $ echo 262146 > /sys/kernel/debug/ext4/pmem0/fault_inject/inject_inode
> $ echo inode_checksum > /sys/kernel/debug/ext4/pmem0/fault_inject/inject_faults
> $ echo 1 > /sys/kernel/debug/ext4/pmem0/fault_inject/enable
> $ echo 3 > /proc/sys/vm/drop_caches ##drop cache
> $ stat /mnt/dir/foo
>   stat: cannot statx '/mnt/dir/foo': Bad message
> 
> The kmesg print the injection location.
> 
> [  461.433817] FAULT_INJECTION: forcing a failure.
> [  461.433817] name fault_inject, interval 1, probability 100, space 0, times 1
> ...
> [  461.438609] Call Trace:
> [  461.438875]  <TASK>
> [  461.439116]  ? dump_stack_lvl+0x73/0xa3
> [  461.439534]  ? dump_stack+0x13/0x1f
> [  461.439909]  ? should_fail.cold+0x4a/0x57
> [  461.440346]  ? ext4_should_fail.cold+0x11f/0x135
> [  461.440833]  ? __ext4_iget+0x407/0x1410
> [  461.441245]  ? ext4_lookup+0x1be/0x350
> [  461.441650]  ? __lookup_slow+0xb9/0x1f0
> [  461.442070]  ? lookup_slow+0x46/0x70
> [  461.442463]  ? walk_component+0x13e/0x230
> [  461.442890]  ? path_lookupat.isra.0+0x8f/0x200
> [  461.443369]  ? filename_lookup+0xd6/0x240
> [  461.443798]  ? vfs_statx+0xa6/0x200
> [  461.444186]  ? do_statx+0x48/0xc0
> [  461.444546]  ? __might_sleep+0x56/0xc0
> [  461.444950]  ? should_fail_usercopy+0x19/0x30
> [  461.445424]  ? strncpy_from_user+0x33/0x2a0
> [  461.445870]  ? getname_flags+0x95/0x330
> [  461.446288]  ? switch_fpu_return+0x27/0x1e0
> [  461.446736]  ? __x64_sys_statx+0x90/0xd0
> [  461.447160]  ? do_syscall_64+0x3b/0x90
> [  461.447563]  ? entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [  461.448122]  </TASK>
> [  461.448395] EXT4-fs error (device pmem0): ext4_lookup:1840: inode #262146: comm stat: iget: checksum invalid
> 
> Thanks,
> Yi.
> 
> 
> Zhang Yi (12):
>   ext4: add debugfs interface
>   ext4: introduce fault injection facility
>   ext4: add several checksum fault injection
>   ext4: add bitmaps I/O fault injection
>   ext4: add inode I/O fault injection
>   ext4: add extent block I/O fault injection
>   ext4: add dirblock I/O fault injection
>   ext4: call ext4_xattr_get_block() when getting xattr block
>   ext4: add xattr block I/O fault injection
>   ext4: add symlink block I/O fault injection
>   ext4: add journal related fault injection
>   ext4: remove simulate fail facility
> 
>  fs/ext4/Kconfig     |   9 ++
>  fs/ext4/balloc.c    |  14 ++-
>  fs/ext4/bitmap.c    |   4 +
>  fs/ext4/dir.c       |   3 +
>  fs/ext4/ext4.h      | 181 +++++++++++++++++++++++++++++--------
>  fs/ext4/ext4_jbd2.c |  22 +++--
>  fs/ext4/ext4_jbd2.h |   5 +
>  fs/ext4/extents.c   |   7 ++
>  fs/ext4/ialloc.c    |  24 +++--
>  fs/ext4/inode.c     |  26 ++++--
>  fs/ext4/namei.c     |  14 ++-
>  fs/ext4/super.c     |   7 +-
>  fs/ext4/symlink.c   |   4 +
>  fs/ext4/sysfs.c     | 183 +++++++++++++++++++++++++++++++++++--
>  fs/ext4/xattr.c     | 216 +++++++++++++++++++-------------------------
>  15 files changed, 515 insertions(+), 204 deletions(-)
> 

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