linux-ext4 - Re: [RFC] ext4: Fix fs can't panic when abort by user

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Date:   Fri, 9 Apr 2021 18:41:34 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Ye Bin <yebin10@...wei.com>
Cc:     adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC] ext4: Fix fs can't panic when abort by user

On Fri, Apr 09, 2021 at 05:28:54PM -0400, Theodore Ts'o wrote:
> I'll apply the patch with a modified commit description to warn of
> this particular change in behavior.

Applied with the following commit description:

    ext4: always panic when errors=panic is specified
    
    Before commit 014c9caa29d3 ("ext4: make ext4_abort() use
    __ext4_error()"), the following series of commands would trigger a
    panic:
    
    1. mount /dev/sda -o ro,errors=panic test
    2. mount /dev/sda -o remount,abort test
    
    After commit 014c9caa29d3, remounting a file system using the test
    mount option "abort" will no longer trigger a panic.  This commit will
    restore the behaviour immediately before commit 014c9caa29d3.
    (However, note that the Linux kernel's behavior has not been
    consistent; some previous kernel versions, including 5.4 and 4.19
    similarly did not panic after using the mount option "abort".)
    
    This also makes a change to long-standing behaviour; namely, the
    following series commands will now cause a panic, when previously it
    did not:
    
    1. mount /dev/sda -o ro,errors=panic test
    2. echo test > /sys/fs/ext4/sda/trigger_fs_error
    
    However, this makes ext4's behaviour much more consistent, so this is
    a good thing.
    
    Fixes: 014c9caa29d3 ("ext4: make ext4_abort() use __ext4_error()")
    Signed-off-by: Ye Bin <yebin10@...wei.com>
    Link: https://lore.kernel.org/r/20210401081903.3421208-1-yebin10@huawei.com
    Signed-off-by: Theodore Ts'o <tytso@....edu>