+
+static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, uid_t uid)
+{
+ struct p9_fid *fid, *ret;
+
+ fid = v9fs_fid_lookup_with_uid(dentry, uid, 0);
+ if (IS_ERR(fid))
+ return fid;
+
+ ret = p9_client_walk(fid, 0, NULL, 1);
+ return ret;
+}
+
+struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
+{
+ int err, flags;
+ struct p9_fid *fid;
+ struct v9fs_session_info *v9ses;
+
+ v9ses = v9fs_dentry2v9ses(dentry);
+ fid = v9fs_fid_clone_with_uid(dentry, 0);
+ if (IS_ERR(fid))
+ goto error_out;
+ /*
+ * writeback fid will only be used to write back the
+ * 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.
+ */
+ 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);
+ goto error_out;
+ }
+error_out:
+ return fid;
+}