9p: Define and implement TLINK for 9P2000.L

This patch adds a helper function to get the dentry from inode and
uses it in creating a Hardlink

SYNOPSIS

size[4] Tlink tag[2] dfid[4] oldfid[4] newpath[s]

size[4] Rlink tag[2]

DESCRIPTION

Create a link 'newpath' in directory pointed by dfid linking to oldfid path.

[sripathik@in.ibm.com : p9_client_link should not free req structure
if p9_client_rpc has returned an error.]
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

include/net/9p/9p.h

@@ -139,6 +139,8 @@ enum p9_msg_t {
 	P9_RSETATTR,
 	P9_TREADDIR = 40,
 	P9_RREADDIR,
+	P9_TLINK = 70,
+	P9_RLINK,
 	P9_TVERSION = 100,
 	P9_RVERSION,
 	P9_TAUTH = 102,

include/net/9p/client.h

@@ -226,6 +226,7 @@ struct p9_fid *p9_client_walk(struct p9_fid *oldfid, int nwname, char **wnames,
 int p9_client_open(struct p9_fid *fid, int mode);
 int p9_client_fcreate(struct p9_fid *fid, char *name, u32 perm, int mode,
 							char *extension);
+int p9_client_link(struct p9_fid *fid, struct p9_fid *oldfid, char *newname);
 int p9_client_clunk(struct p9_fid *fid);
 int p9_client_remove(struct p9_fid *fid);
 int p9_client_read(struct p9_fid *fid, char *data, char __user *udata,

net/9p/client.c

@@ -1095,6 +1095,25 @@ int p9_client_fcreate(struct p9_fid *fid, char *name, u32 perm, int mode,
 }
 EXPORT_SYMBOL(p9_client_fcreate);
 
+int p9_client_link(struct p9_fid *dfid, struct p9_fid *oldfid, char *newname)
+{
+	struct p9_client *clnt;
+	struct p9_req_t *req;
+
+	P9_DPRINTK(P9_DEBUG_9P, ">>> TLINK dfid %d oldfid %d newname %s\n",
+			dfid->fid, oldfid->fid, newname);
+	clnt = dfid->clnt;
+	req = p9_client_rpc(clnt, P9_TLINK, "dds", dfid->fid, oldfid->fid,
+			newname);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	P9_DPRINTK(P9_DEBUG_9P, "<<< RLINK\n");
+	p9_free_req(clnt, req);
+	return 0;
+}
+EXPORT_SYMBOL(p9_client_link);
+
 int p9_client_clunk(struct p9_fid *fid)
 {
 	int err;