linux-kernel - [PATCH v5 0/3] Fix an error caused by improperly dirtied buffer

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Message-Id: <20240829085407.3331490-1-zhangshida@kylinos.cn>
Date: Thu, 29 Aug 2024 16:54:04 +0800
From: zhangshida <starzhangzsd@...il.com>
To: tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.com,
	ebiggers@...nel.org
Cc: linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	zhangshida@...inos.cn,
	starzhangzsd@...il.com
Subject: [PATCH v5 0/3] Fix an error caused by improperly dirtied buffer

From: Shida Zhang <zhangshida@...inos.cn>

Hi all,

On an old kernel version(4.19, ext3, data=journal, pagesize=64k),
an assertion failure will occasionally be triggered by the line below:
---------
jbd2_journal_commit_transaction
{
...
J_ASSERT_BH(bh, !buffer_dirty(bh));
/*
* The buffer on BJ_Forget list and not jbddirty means
...
}
---------

The same condition may also be applied to the lattest kernel version.

This patch set fixes it by: 
1.Fix a small bug for ext4_journalled_zero_new_buffers first.(patch 1)
2.Replace the __block_write_begin with the hoisted
  ext4_block_write_begin().(patch 2)
3.Trace the user data dirtying in ext4_block_write_begin().(patch 3)

Changes since v4: 
- At first, we fix a bug in ext4_journalled_zero_new_buffers, as suggested
  by Jan.
- In patch 2, clean up the related comment. And remove the #ifdef in 
  ext4_block_write_begin(), as suggested by Eric. 
- Add some comments in patch 3.

[4] Version 4:
https://lore.kernel.org/linux-ext4/20240823013329.1996741-1-zhangshida@kylinos.cn/
Changes since v3: 
- Ditch the patch 3 in v3, because some other code paths can set the 
  buffer dirty:
        ext4_write_begin
                ext4_block_write_begin
                        create_empty_buffers
                                set_buffer_dirty 

[3] Version 3:
https://lore.kernel.org/linux-ext4/20240810082814.3709867-1-zhangshida@kylinos.cn/
Changes since v2: 
- Adjust the applied order of patch 1 and patch 2 in v1. 
- Reword the commit message.
- Remove some superfluous logic in patch 2 and patch 3.

[2] Version 2:
https://lore.kernel.org/linux-ext4/20240809064606.3490994-2-zhangshida@kylinos.cn/
Changes since v1: 
- v1 use a hack into jbd2 to fix the bug while v2 choose to journal
  the dirty data in *_block_write_begin.

[1] Version 1:
https://lore.kernel.org/linux-ext4/20240720062356.2522658-1-zhangshida@kylinos.cn/


Shida Zhang (3):
  ext4: persist the new uptodate buffers in
    ext4_journalled_zero_new_buffers
  ext4: hoist ext4_block_write_begin and replace the __block_write_begin
  ext4: fix a potential assertion failure due to improperly dirtied
    buffer

 fs/ext4/ext4.h   |  3 +++
 fs/ext4/inline.c | 11 ++++----
 fs/ext4/inode.c  | 65 ++++++++++++++++++++++++++++--------------------
 3 files changed, 47 insertions(+), 32 deletions(-)

-- 
2.33.0