For filesystems such as nilfs2 and xfs that use block_page_mkwrite, modify that
function to wait for pending writeback before allowing the page to become
writable.  This is needed to stabilize pages during writeback for those two
filesystems.

Slight rework based on Jan Kara's suggestion.

Signed-off-by: Darrick J. Wong <redacted>
---

 fs/buffer.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index a08bb8e..0e7fa16 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c

@@ -2367,8 +2367,10 @@ block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 			ret = VM_FAULT_OOM;
 		else /* -ENOSPC, -EIO, etc */
 			ret = VM_FAULT_SIGBUS;
-	} else
+	} else {
+		wait_on_page_writeback(page);
 		ret = VM_FAULT_LOCKED;
+	}
 
 out:
 	return ret;