[Virtio-fs] [PATCH 1/2] fuse: disable atomic_o_trunc if no_open is enabled

[Jeffle Xu]

From: Liu Bo <bo.liu at linux.alibaba.com>

When 'no_open' is used by virtiofsd, guest kernel won't send OPEN request
any more.  However, with atomic_o_trunc, SETATTR request is also omitted in
OPEN(O_TRUNC) so that the backend file is not truncated.  With a following
GETATTR, inode size on guest side is updated to be same with that on host
side, the end result is that O_TRUNC semantic is broken.

This disables atomic_o_trunc as well if with no_open.

Reviewed-by: Peng Tao <tao.peng at linux.alibaba.com>
Signed-off-by: Liu Bo <bo.liu at linux.alibaba.com>
Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
---
 fs/fuse/file.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index b494ff08f08c..1231128f8dd6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -151,10 +151,16 @@ struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid,
 			fuse_file_free(ff);
 			return ERR_PTR(err);
 		} else {
-			if (isdir)
+			if (isdir) {
 				fc->no_opendir = 1;
-			else
+			} else {
 				fc->no_open = 1;
+				/*
+				 * In case of no_open, disable atomic_o_trunc as
+				 * well.
+				 */
+				fc->atomic_o_trunc = 0;
+			}
 		}
 	}
 
-- 
2.27.0