[PATCH 3/3] fuse: write back dirty pages before direct write in direct_io_relax mode

[Hao Xu <hao.xu@linux.dev>]

From: Hao Xu <howeyxu@tencent.com>

In direct_io_relax mode, there can be shared mmaped files and thus dirty
pages in its page cache. Therefore those dirty pages should be written
back to backend before direct write to avoid data loss.

Signed-off-by: Hao Xu <howeyxu@tencent.com>
---
 fs/fuse/file.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 176f719f8fc8..7c9167c62bf6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1485,6 +1485,13 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
 	if (!ia)
 		return -ENOMEM;
 
+	if (fopen_direct_write && fc->direct_io_relax) {
+		res = filemap_write_and_wait_range(mapping, pos, pos + count - 1);
+		if (res) {
+			fuse_io_free(ia);
+			return res;
+		}
+	}
 	if (!cuse && fuse_range_is_writeback(inode, idx_from, idx_to)) {
 		if (!write)
 			inode_lock(inode);
-- 
2.25.1