From: "Theodore Ts'o" <tytso@mit.edu>
To: Ye Bin <yebin10@huawei.com>
Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC] ext4: Fix fs can't panic when abort by user
Date: Fri, 9 Apr 2021 17:28:54 -0400 [thread overview]
Message-ID: <YHDHFv99m3A6jQjP@mit.edu> (raw)
In-Reply-To: <20210401081903.3421208-1-yebin10@huawei.com>
On Thu, Apr 01, 2021 at 04:19:03PM +0800, Ye Bin wrote:
> Test steps:
> 1. mount /dev/sda -o errors=panic test
> 2. mount /dev/sda -o remount,ro test
> 3. mount /dev/sda -o remount,abort test
>
> Before 014c9caa29d3 not been merged there will trigger panic. But
> 014c9caa29d3 change this behavior.
This makes sense, but I'll note this behavior has changed over time.
root@kvm-xfstests:~# mount -o errors=panic /dev/vdc /vdc
[ 20.252713] EXT4-fs (vdc): mounted filesystem with ordered data mode. Opts: errors=panic
root@kvm-xfstests:~# mount -o remount,ro /dev/vdc
[ 24.832448] EXT4-fs (vdc): re-mounted. Opts: (null)
root@kvm-xfstests:~# mount -o remount,abort /dev/vdc
[ 30.833543] EXT4-fs error (device vdc): ext4_remount:5340: Abort forced by user
mount: /vdc: cannot remount /dev/vdc read-write, is write-protected.
root@kvm-xfstests:~# mount -o remount,abort,ro /dev/vdc
[ 34.545549] EXT4-fs error (device vdc): ext4_remount:5340: Abort forced by user
[ 34.555475] EXT4-fs (vdc): re-mounted. Opts: abort
root@kvm-xfstests:~# uname -a
Linux kvm-xfstests 4.19.163-xfstests #1 SMP Sat Dec 19 23:55:11 EST 2020 x86_64 GNU/Linux
root@kvm-xfstests:~#
The same is true for the 5.4 kernel.
I do agree that it *should* force a panic, and the fact that
superblock is read-only shouldn't make a difference as to how
errors=panic is handled.
So I think the patch is correct, but I'll note that it also changes
this case:
1) mount -o /dev/sda -o ro,errors=panic test
2) echo test > /sys/fs/ext4/sda/trigger_fs_error
With this patch, this will also now panic, whereas before, an
ext4_error() would not trigger a panic. I think that's better because
it makes things more consistent --- but it is a change in behavior
which could potentially surprise some people. But since they can
easily get the previous behavior with an explicit "mount -o
ro,errors=continue", I think that's acceptable.
I'll apply the patch with a modified commit description to warn of
this particular change in behavior.
- Ted
next prev parent reply other threads:[~2021-04-09 21:29 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 8:19 [RFC] ext4: Fix fs can't panic when abort by user Ye Bin
2021-04-09 21:28 ` Theodore Ts'o [this message]
2021-04-09 22:41 ` Theodore Ts'o
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