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

[Heming Zhao]

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().

- Heming
> 
> >  unlock:
> >  	up_write(&oi->ip_alloc_sem);
> > +
> > +	/* everything looks good, let's start the cleanup */
> > +	if (!ret && dwc->dw_orphaned) {
> > +		BUG_ON(dwc->dw_writer_pid != task_pid_nr(current));
> > +
> > +		ret = ocfs2_del_inode_from_orphan(osb, inode, di_bh, 0, 0);
> > +		if (ret < 0)
> > +			mlog_errno(ret);
> > +	}
> >  	ocfs2_inode_unlock(inode, 1);
> >  	brelse(di_bh);
> >  out:
>