Re: [PATCH v7 1/1] ocfs2: split transactions in dio completion to avoid credit exhaustion

[Joseph Qi]

On 4/2/26 6:06 PM, 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..9be43ea98930 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 (!handle) {
> +		handle = ocfs2_start_trans(osb, credits);
> +		if (IS_ERR(handle)) {
> +			ret = PTR_ERR(handle);
> +			mlog_errno(ret);
> +			goto unlock;
> +		}
> +	}

I don't think it's a good idea to change it like this.
e.g. It has exactly OCFS2_DIO_MARK_EXTENT_BATCH entries, and don't have
to update inode size, now it will do one more meanlingless transaction
operation.

So the least change is just check 'handle' before commit based on v6.

Joseph

>  	if (end > i_size_read(inode)) {
>  		ret = ocfs2_set_inode_size(handle, inode, di_bh, end);
>  		if (ret < 0)
>  			mlog_errno(ret);
>  	}
> +
>  commit:
>  	ocfs2_commit_trans(osb, handle);
>  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: