[RESEND PATCH] ceph: don't truncate file in atomic_open

[Hu Weiwen <sehuww@mail.scut.edu.cn>]

Clear O_TRUNC from the flags sent in the MDS create request.

`atomic_open' is called before permission check. We should not do any
modification to the file here. The caller will do the truncation
afterward.

Fixes: 124e68e74099 ("ceph: file operations")
Signed-off-by: Hu Weiwen <sehuww@mail.scut.edu.cn>
---
rebased onto ceph_client repo testing branch

 fs/ceph/file.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 296fd1c7ece8..289e66e9cbb0 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -745,6 +745,11 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 	err = ceph_wait_on_conflict_unlink(dentry);
 	if (err)
 		return err;
+	/*
+	 * Do not truncate the file, since atomic_open is called before the
+	 * permission check. The caller will do the truncation afterward.
+	 */
+	flags &= ~O_TRUNC;
 
 retry:
 	if (flags & O_CREAT) {
@@ -836,9 +841,7 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
 	req->r_new_inode = new_inode;
 	new_inode = NULL;
-	err = ceph_mdsc_do_request(mdsc,
-				   (flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
-				   req);
+	err = ceph_mdsc_do_request(mdsc, (flags & O_CREAT) ? dir : NULL, req);
 	if (err == -ENOENT) {
 		dentry = ceph_handle_snapdir(req, dentry);
 		if (IS_ERR(dentry)) {
-- 
2.25.1