[Ocfs2-devel] [PATCH] ocfs2: fix missing reset j_num_trans for sync
Heming Zhao
heming.zhao at suse.com
Sat Apr 22 08:55:32 UTC 2023
Sorry, please pause this patch review.
When I was investigating fstest generic failed case 347 361, I found
the wake_up() action should move out the 'if()' area. The correct way
is calling wake_up() unconditionally.
Thanks,
Heming
On 4/21/23 4:36 PM, Heming Zhao wrote:
> fstest generic case 266 272 281 trigger hanging issue when umount.
>
> I use 266 to describe the root cause.
>
> ```
> 49 _dmerror_unmount
> 50 _dmerror_mount
> 51
> 52 echo "Compare files"
> 53 md5sum $testdir/file1 | _filter_scratch
> 54 md5sum $testdir/file2 | _filter_scratch
> 55
> 56 echo "CoW and unmount"
> 57 sync
> 58 _dmerror_load_error_table
> 59 urk=$($XFS_IO_PROG -f -c "pwrite -S 0x63 -b $bufsize 0 $filesize" \
> 60 -c "fdatasync" $testdir/file2 2>&1)
> 61 echo $urk >> $seqres.full
> 62 echo "$urk" | grep -q "error" || _fail "pwrite did not fail"
> 63
> 64 echo "Clean up the mess"
> 65 _dmerror_unmount
> ```
>
> After line 49 50 umount & mount ocfs2 dev, this case run md5sum to
> verify target file. line 57 run 'sync' before line 58 changes the dm
> target from dm-linear to dm-error. this case is hanging at line 65.
>
> In 266, md5sum calls jbd2 trans pair: ocfs2_[start|commit]_trans to
> do journal job. but there is only ->j_num_trans+1 in ocfs2_start_trans,
> the ocfs2_commit_trans doesn't do reduction operation.
>
> call flow:
> ```
> [md5sum]
> vfs_read
> ocfs2_file_read_iter
> ocfs2_inode_lock_atime
> ocfs2_update_inode_atime
> + ocfs2_start_trans //atomic_inc j_num_trans
> + ...
> + ocfs2_commit_trans//no modify j_num_trans
>
> sync //no modify j_num_trans
>
> _dmerror_load_error_table //all write will return error after this line
>
> _dmerror_unmount //found j_num_trans is not zero, run commit thread
> //but the underlying dev is dm-error, journaling IO
> //failed all the time and keep going to retry.
> ```
>
> *** How to fix ***
>
> kick commit thread in sync path, which can reset j_num_trans to 0.
>
> Signed-off-by: Heming Zhao <heming.zhao at suse.com>
> ---
> fs/ocfs2/super.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
> index 0b0e6a132101..9929320bd967 100644
> --- a/fs/ocfs2/super.c
> +++ b/fs/ocfs2/super.c
> @@ -408,6 +408,9 @@ static int ocfs2_sync_fs(struct super_block *sb, int wait)
>
> if (jbd2_journal_start_commit(osb->journal->j_journal,
> &target)) {
> + /* kick commit thread to reset journal->j_num_trans */
> + wake_up(&osb->checkpoint_event);
> +
> if (wait)
> jbd2_log_wait_commit(osb->journal->j_journal,
> target);
>
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