linux-ext4 - Re: [PATCH RFC v2] ext4:fix warning in mark_buffer_dirty as IO error when mount with errors=continue

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Message-ID: <YN3YURikQ5SdEFLs@mit.edu>
Date:   Thu, 1 Jul 2021 10:59:29 -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, jack@...e.cz
Subject: Re: [PATCH RFC v2] ext4:fix warning in mark_buffer_dirty as IO error
 when mount with errors=continue

Thanks, applied.  I reworded the commit description a bit, putting the
explanation first, and cleaning up the text a bit to make it more
readable:

commit 558d6450c7755aa005d89021204b6cdcae5e848f
Author: Ye Bin <yebin10@...wei.com>
Date:   Tue Jun 15 17:05:37 2021 +0800

    ext4: fix WARN_ON_ONCE(!buffer_uptodate) after an error writing the superblock
    
    If a writeback of the superblock fails with an I/O error, the buffer
    is marked not uptodate.  However, this can cause a WARN_ON to trigger
    when we attempt to write superblock a second time.  (Which might
    succeed this time, for cerrtain types of block devices such as iSCSI
    devices over a flaky network.)
    
    Try to detect this case in flush_stashed_error_work(), and also change
    __ext4_handle_dirty_metadata() so we always set the uptodate flag, not
    just in the nojournal case.
    
    Before this commit, this problem can be repliciated via:
    
    1. dmsetup  create dust1 --table  '0 2097152 dust /dev/sdc 0 4096'
    2. mount  /dev/mapper/dust1  /home/test
    3. dmsetup message dust1 0 addbadblock 0 10
    4. cd /home/test
    5. echo "XXXXXXX" > t
    
    After a few seconds, we got following warning:

    ... <rest of commit description was unchanged, and omitted here>