fs/9p: Open writeback fid in O_SYNC mode

Older version of protocol don't support tsyncfs operation.
So for them force a O_SYNC flag on the server

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index cd63e002d826..99a1a7b08634 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -286,9 +286,11 @@ static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, uid_t uid)
 
 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
 {
-        int err;
+        int err, flags;
         struct p9_fid *fid;
+        struct v9fs_session_info *v9ses;
 
+        v9ses = v9fs_inode2v9ses(dentry->d_inode);
         fid = v9fs_fid_clone_with_uid(dentry, 0);
         if (IS_ERR(fid))
                 goto error_out;
@@ -297,8 +299,17 @@ struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
          * dirty pages. We always request for the open fid in read-write
          * mode so that a partial page write which result in page
          * read can work.
+         *
+         * we don't have a tsyncfs operation for older version
+         * of protocol. So make sure the write back fid is
+         * opened in O_SYNC mode.
          */
-        err = p9_client_open(fid, O_RDWR);
+        if (!v9fs_proto_dotl(v9ses))
+                flags = O_RDWR | O_SYNC;
+        else
+                flags = O_RDWR;
+
+        err = p9_client_open(fid, flags);
         if (err < 0) {
                 p9_client_clunk(fid);
                 fid = ERR_PTR(err);