[PATCH v4 0/2] Fix an error caused by improperly dirtied buffer

[zhangshida <starzhangzsd@gmail.com>]

From: Shida Zhang <zhangshida@kylinos.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.Replace the __block_write_begin with the hoisted
  ext4_block_write_begin().(patch 1)
2.Trace the user data dirtying in ext4_block_write_begin().(patch 2)


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 (2):
  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  | 51 +++++++++++++++++++++++++-----------------------
 3 files changed, 36 insertions(+), 29 deletions(-)

-- 
2.33.0