[PATCH v7 0/1] ocfs2: split transactions in dio completion to avoid credit exhaustion

[PATCH v7 0/1] ocfs2: split transactions in dio completion to avoid credit exhaustion

[Heming Zhao]

For easier merging, this patch is based on Joseph's patch [1].

v6->v7:
fix logic error regarding "handle == NULL".

v5->v6:
add a check for handle before updating i_size.

v4->v5:
change update inode size and remove orphan logic.
add above change in commit log.

v3->v4:
Remove [patch 2/2] as the revert operation is incorrect.

v2->v3:
Following the discussion, use 'batch' and 'handle' to control
restarting the jbd2 transaction.

v1->v2:
following the review comments, restore the i_size update code in
ocfs2_dio_end_io_write().

the runtime of the test script [2].
real    1m48.148s
user    0m0.344s
sys     0m22.684s

[1]:
https://lore.kernel.org/ocfs2-devel/46yilbaq5z5x6gdfdpoa6lprf6sf3gbxriuku2odje4kx4bovf@jd735cphfutz/T/#t 
[2]:
https://lore.kernel.org/ocfs2-devel/75f89a17-213b-42a0-a30e-d52fb2d077a6@linux.alibaba.com/T/#mbe2b5f52ee249178e1ad4c76d964de2dc818eb32

Heming Zhao (1):
  ocfs2: split transactions in dio completion to avoid credit exhaustion

 fs/ocfs2/aops.c | 71 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 43 insertions(+), 28 deletions(-)

-- 
2.43.0

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

[Heming Zhao]

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@suse.cz>
Suggested-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Heming Zhao <heming.zhao@suse.com>
---
 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;
+		}
+	}
 	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:
-- 
2.43.0

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@suse.cz>
> Suggested-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Heming Zhao <heming.zhao@suse.com>
> ---
>  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: