[PATCH v2 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 each extent in a separate 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 removes the only call to ocfs2_assure_trans_credits(), which
was introduced by commit be346c1a6eeb ("ocfs2: fix DIO failure due to
insufficient transaction credits").

Finally, thanks to Jans for providing the bug fix prototype and suggestions.

Suggested-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Heming Zhao <heming.zhao@xxxxxxxx>
---
 fs/ocfs2/aops.c | 58 ++++++++++++++++++++++++-------------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 09146b43d1f0..91997b330d39 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2294,18 +2294,6 @@ 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;
 
@@ -2326,44 +2314,56 @@ 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) {
-		ret = ocfs2_assure_trans_credits(handle, credits);
-		if (ret < 0) {
+		handle = ocfs2_start_trans(osb, credits);
+		if (IS_ERR(handle)) {
+			ret = PTR_ERR(handle);
 			mlog_errno(ret);
 			break;
 		}
+		ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
+					      OCFS2_JOURNAL_ACCESS_WRITE);
+		if (ret) {
+			mlog_errno(ret);
+			ocfs2_commit_trans(osb, handle);
+			break;
+		}
 		ret = ocfs2_mark_extent_written(inode, &et, handle,
 						ue->ue_cpos, 1,
 						ue->ue_phys,
 						meta_ac, &dealloc);
 		if (ret < 0) {
 			mlog_errno(ret);
+			ocfs2_commit_trans(osb, handle);
 			break;
 		}
+		ocfs2_commit_trans(osb, handle);
 	}
 
 	if (end > i_size_read(inode)) {
+		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);
+		ocfs2_commit_trans(osb, handle);
 	}
-commit:
-	ocfs2_commit_trans(osb, handle);
+
 unlock:
 	up_write(&oi->ip_alloc_sem);
+
+	/* everything looks good, let's start the cleanup */
+	if (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