Re: [PATCH v6 1/1] ocfs2: split transactions in dio completion to avoid credit exhaustion

[Joseph Qi]

On 4/2/26 3:43 PM, Heming Zhao wrote:
> On Thu, Apr 02, 2026 at 03:07:10PM +0800, Joseph Qi wrote:
>>
>>
>> On 4/2/26 10:26 AM, Heming Zhao wrote:
>>> During ocfs2 dio operations, JBD2 may report warnings via following
>>> call trace:
>>> ocfs2_dio_end_io_write
>>>  ocfs2_mark_extent_written
>>>   ocfs2_change_extent_flag
>>>    ocfs2_split_extent
>>>     ocfs2_try_to_merge_extent
>>>      ocfs2_extend_rotate_transaction
>>>       ocfs2_extend_trans
>>>        jbd2__journal_restart
>>>         start_this_handle
>>>          output: JBD2: kworker/6:2 wants too many credits credits:5450 rsv_credits:0 max:5449
>>>
>>> To prevent exceeding the credits limit, modify ocfs2_dio_end_io_write() to
>>> handle extents in a batch of transaction.
>>>
>>> Additionally, relocate ocfs2_del_inode_from_orphan(). The orphan inode should
>>> only be removed from the orphan list after the extent tree update is complete.
>>> This ensures that if a crash occurs in the middle of extent tree updates, we
>>> won't leave stale blocks beyond EOF.
>>>
>>> This patch also changes the logic for updating the inode size and removing
>>> orphan, making it similar to ext4_dio_write_end_io(). Both operations are
>>> performed only when everything looks good.
>>>
>>> Finally, thanks to Jans and Joseph for providing the bug fix prototype and
>>> suggestions.
>>>
>>> Suggested-by: Jan Kara <jack@xxxxxxx>
>>> Suggested-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
>>> Reviewed-by: Jan Kara <jack@xxxxxxx>
>>> Signed-off-by: Heming Zhao <heming.zhao@xxxxxxxx>
>>> ---
>>>  fs/ocfs2/aops.c | 71 ++++++++++++++++++++++++++++++-------------------
>>>  1 file changed, 43 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>>> index 09146b43d1f0..0c88f751ffd5 100644
>>> --- a/fs/ocfs2/aops.c
>>> +++ b/fs/ocfs2/aops.c
>>> @@ -37,6 +37,8 @@
>>>  #include "namei.h"
>>>  #include "sysfile.h"
>>>  
>>> +#define OCFS2_DIO_MARK_EXTENT_BATCH 200
>>> +
>>>  static int ocfs2_symlink_get_block(struct inode *inode, sector_t iblock,
>>>  				   struct buffer_head *bh_result, int create)
>>>  {
>>> @@ -2277,7 +2279,7 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  	struct ocfs2_alloc_context *meta_ac = NULL;
>>>  	handle_t *handle = NULL;
>>>  	loff_t end = offset + bytes;
>>> -	int ret = 0, credits = 0;
>>> +	int ret = 0, credits = 0, batch = 0;
>>>  
>>>  	ocfs2_init_dealloc_ctxt(&dealloc);
>>>  
>>> @@ -2294,18 +2296,6 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  		goto out;
>>>  	}
>>>  
>>> -	/* Delete orphan before acquire i_rwsem. */
>>> -	if (dwc->dw_orphaned) {
>>> -		BUG_ON(dwc->dw_writer_pid != task_pid_nr(current));
>>> -
>>> -		end = end > i_size_read(inode) ? end : 0;
>>> -
>>> -		ret = ocfs2_del_inode_from_orphan(osb, inode, di_bh,
>>> -				!!end, end);
>>> -		if (ret < 0)
>>> -			mlog_errno(ret);
>>> -	}
>>> -
>>>  	down_write(&oi->ip_alloc_sem);
>>>  	di = (struct ocfs2_dinode *)di_bh->b_data;
>>>  
>>> @@ -2326,24 +2316,25 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  
>>>  	credits = ocfs2_calc_extend_credits(inode->i_sb, &di->id2.i_list);
>>>  
>>> -	handle = ocfs2_start_trans(osb, credits);
>>> -	if (IS_ERR(handle)) {
>>> -		ret = PTR_ERR(handle);
>>> -		mlog_errno(ret);
>>> -		goto unlock;
>>> -	}
>>> -	ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
>>> -				      OCFS2_JOURNAL_ACCESS_WRITE);
>>> -	if (ret) {
>>> -		mlog_errno(ret);
>>> -		goto commit;
>>> -	}
>>> -
>>>  	list_for_each_entry(ue, &dwc->dw_zero_list, ue_node) {
>>> +		if (!handle) {
>>> +			handle = ocfs2_start_trans(osb, credits);
>>> +			if (IS_ERR(handle)) {
>>> +				ret = PTR_ERR(handle);
>>> +				mlog_errno(ret);
>>> +				goto unlock;
>>> +			}
>>> +			ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
>>> +					OCFS2_JOURNAL_ACCESS_WRITE);
>>> +			if (ret) {
>>> +				mlog_errno(ret);
>>> +				goto commit;
>>> +			}
>>> +		}
>>>  		ret = ocfs2_assure_trans_credits(handle, credits);
>>>  		if (ret < 0) {
>>>  			mlog_errno(ret);
>>> -			break;
>>> +			goto commit;
>>>  		}
>>>  		ret = ocfs2_mark_extent_written(inode, &et, handle,
>>>  						ue->ue_cpos, 1,
>>> @@ -2351,19 +2342,43 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  						meta_ac, &dealloc);
>>>  		if (ret < 0) {
>>>  			mlog_errno(ret);
>>> -			break;
>>> +			goto commit;
>>> +		}
>>> +
>>> +		if (++batch == OCFS2_DIO_MARK_EXTENT_BATCH) {
>>> +			ocfs2_commit_trans(osb, handle);
>>> +			handle = NULL;
>>> +			batch = 0;
>>>  		}
>>>  	}
>>>  
>>>  	if (end > i_size_read(inode)) {
>>> +		if (!handle) {
>>> +			handle = ocfs2_start_trans(osb, credits);
>>> +			if (IS_ERR(handle)) {
>>> +				ret = PTR_ERR(handle);
>>> +				mlog_errno(ret);
>>> +				goto unlock;
>>> +			}
>>> +		}
>>>  		ret = ocfs2_set_inode_size(handle, inode, di_bh, end);
>>>  		if (ret < 0)
>>>  			mlog_errno(ret);
>>>  	}
>>> +
>>>  commit:
>>>  	ocfs2_commit_trans(osb, handle);
>>
>> Seems checking 'handle' is still missing here.
>>
>> Joseph
> 
> I have a different view.
> In the list_for_each_entry(), if it finishes because the condition
> (++batch == OCFS2_DIO_MARK_EXTENT_BATCH) is met, the handle will be null.
> However, it will be initialized later within the i_size update block.
> In my view, the handle must be non-null before entering ocfs2_commit_trans().
> 

Ummm... inode size update is conditional, right?

Thanks,
Joseph