在 2020/11/20 10:54, yangerkun 写道:
在 2020/11/19 21:12, Mauricio Oliveira 写道:
On Thu, Nov 19, 2020 at 1:25 AM yangerkun <yangerkun@xxxxxxxxxx> wrote:
在 2020/11/16 21:50, Mauricio Oliveira 写道:
Hi Kun,
On Sat, Nov 14, 2020 at 5:18 AM yangerkun <yangerkun@xxxxxxxxxx> wrote:
While using ext4 with data=journal(3.10 kernel), we meet a problem
that
we think may never happend...
[...]
Could you please confirm you mean 5.10-rc* kernel instead of 3.10?
(It seems so as you mention a recent commit below.) Thanks!
For now, what I have seen that can dirty buffer directly is
ext4_page_mkwrite(64a9f1449950 ("ext4: data=journal: fixes for
ext4_page_mkwrite()")), and runing ext4_punch_hole with keep_size
/ext4_page_mkwrite parallel can trigger above warning easily.
[...]
Hi,
Sorry for the long delay reply... And thanks a lot for your advise! The
bug trigger with a very low probability. So won't trigger with 5.10 can
not prove no bug exist in 5.10.
No worries, and thanks for following up.
So I understand that the bug report was indeed on 3.10, and 5.10-rcN
is not yet confirmed.
Google a lot and notice that someone before has report the same bug[1].
'3b136499e906 ("ext4: fix data corruption in data=journal mode")' seems
fix the problem. I will try to understand this, and give a analysis
about how to reproduce it!
Cool, thanks!
Thanks,
Kun.
Hi,
The follow step can reproduce the bug[1] reported before easily. And the
bug we meet seems same. Following patch will fix the bug.
3b136499e906 ext4: fix data corruption in data=journal mode
b90197b65518 ext4: use private version of page_zero_new_buffers() for
data=journal mode
1. mkfs.ext4
2. touch $tofile(ino == 12)
3. touch $fromfile(ino == 13) and write 4k to fromfile and sync
mmap $fromfile 4k
and write 4k
to $tofile
...
generic_perform_write
ext4_write_begin
ext4_journal_start
(trans 1)
if (ino == 12) sleep for 30s
... truncate $fromfile
to 0
copied=0,bytes=4k
ext4_journalled_write_end
page_zero_new_buffers
mark_buffer_dirty
write_end_fn
...
__jbd2_journal_file_buffer
test_clear_buffer_dirty
__jbd2_journal_temp_unlink_buffer
this will mark buffer dirty again!
ext4_journal_stop
(trans 1)
trans1 commit
...
ext4_truncate_failed_write
...
journal_unmap_buffer
set_buffer_freed
forget list
...
clear_buffer_jbddirty
...
J_ASSERT_BH(bh,
!buffer_dirty(bh))
^^^^^^^^^^^^^^^^^
trigger the bug...
[1]. https://www.spinics.net/lists/linux-ext4/msg56447.html
Thanks,
Kun.
.
