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

Create a symbolic link

SYNOPSIS

size[4] Tsymlink tag[2] fid[4] name[s] symtgt[s] gid[4]

size[4] Rsymlink tag[2] qid[13]

DESCRIPTION

Create a symbolic link named 'name' pointing to 'symtgt'.
gid represents the effective group id of the caller.
The  permissions of a symbolic link are irrelevant hence it is omitted
from the protocol.
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Reviewed-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_inode.c

@@ -1245,7 +1245,7 @@ static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
 	if (IS_ERR(fid))
 		return PTR_ERR(fid);
 
-	if (!v9fs_proto_dotu(v9ses))
+	if (!v9fs_proto_dotu(v9ses) && !v9fs_proto_dotl(v9ses))
 		return -EBADF;
 
 	st = p9_client_stat(fid);
@@ -1350,6 +1350,99 @@ static int v9fs_vfs_mkspecial(struct inode *dir, struct dentry *dentry,
 	return 0;
 }
 
+/**
+ * v9fs_vfs_symlink_dotl - helper function to create symlinks
+ * @dir: directory inode containing symlink
+ * @dentry: dentry for symlink
+ * @symname: symlink data
+ *
+ * See Also: 9P2000.L RFC for more information
+ *
+ */
+
+static int
+v9fs_vfs_symlink_dotl(struct inode *dir, struct dentry *dentry,
+		const char *symname)
+{
+	struct v9fs_session_info *v9ses;
+	struct p9_fid *dfid;
+	struct p9_fid *fid = NULL;
+	struct inode *inode;
+	struct p9_qid qid;
+	char *name;
+	int err;
+	gid_t gid;
+
+	name = (char *) dentry->d_name.name;
+	P9_DPRINTK(P9_DEBUG_VFS, "v9fs_vfs_symlink_dotl : %lu,%s,%s\n",
+			dir->i_ino, name, symname);
+	v9ses = v9fs_inode2v9ses(dir);
+
+	dfid = v9fs_fid_lookup(dentry->d_parent);
+	if (IS_ERR(dfid)) {
+		err = PTR_ERR(dfid);
+		P9_DPRINTK(P9_DEBUG_VFS, "fid lookup failed %d\n", err);
+		return err;
+	}
+
+	gid = v9fs_get_fsgid_for_create(dir);
+
+	if (gid < 0) {
+		P9_DPRINTK(P9_DEBUG_VFS, "v9fs_get_egid failed %d\n", gid);
+		goto error;
+	}
+
+	/* Server doesn't alter fid on TSYMLINK. Hence no need to clone it. */
+	err = p9_client_symlink(dfid, name, (char *)symname, gid, &qid);
+
+	if (err < 0) {
+		P9_DPRINTK(P9_DEBUG_VFS, "p9_client_symlink failed %d\n", err);
+		goto error;
+	}
+
+	if (v9ses->cache) {
+		/* Now walk from the parent so we can get an unopened fid. */
+		fid = p9_client_walk(dfid, 1, &name, 1);
+		if (IS_ERR(fid)) {
+			err = PTR_ERR(fid);
+			P9_DPRINTK(P9_DEBUG_VFS, "p9_client_walk failed %d\n",
+					err);
+			fid = NULL;
+			goto error;
+		}
+
+		/* instantiate inode and assign the unopened fid to dentry */
+		inode = v9fs_inode_from_fid(v9ses, fid, dir->i_sb);
+		if (IS_ERR(inode)) {
+			err = PTR_ERR(inode);
+			P9_DPRINTK(P9_DEBUG_VFS, "inode creation failed %d\n",
+					err);
+			goto error;
+		}
+		dentry->d_op = &v9fs_cached_dentry_operations;
+		d_instantiate(dentry, inode);
+		err = v9fs_fid_add(dentry, fid);
+		if (err < 0)
+			goto error;
+		fid = NULL;
+	} else {
+		/* Not in cached mode. No need to populate inode with stat */
+		inode = v9fs_get_inode(dir->i_sb, S_IFLNK);
+		if (IS_ERR(inode)) {
+			err = PTR_ERR(inode);
+			goto error;
+		}
+		dentry->d_op = &v9fs_dentry_operations;
+		d_instantiate(dentry, inode);
+	}
+
+error:
+	if (fid)
+		p9_client_clunk(fid);
+
+	return err;
+}
+
 /**
  * v9fs_vfs_symlink - helper function to create symlinks
  * @dir: directory inode containing symlink
@@ -1527,7 +1620,7 @@ static const struct inode_operations v9fs_dir_inode_operations_dotu = {
 	.create = v9fs_vfs_create,
 	.lookup = v9fs_vfs_lookup,
 	.symlink = v9fs_vfs_symlink,
-	.link = v9fs_vfs_link_dotl,
+	.link = v9fs_vfs_link,
 	.unlink = v9fs_vfs_unlink,
 	.mkdir = v9fs_vfs_mkdir,
 	.rmdir = v9fs_vfs_rmdir,
@@ -1540,8 +1633,8 @@ static const struct inode_operations v9fs_dir_inode_operations_dotu = {
 static const struct inode_operations v9fs_dir_inode_operations_dotl = {
 	.create = v9fs_vfs_create,
 	.lookup = v9fs_vfs_lookup,
-	.symlink = v9fs_vfs_symlink,
-	.link = v9fs_vfs_link,
+	.link = v9fs_vfs_link_dotl,
+	.symlink = v9fs_vfs_symlink_dotl,
 	.unlink = v9fs_vfs_unlink,
 	.mkdir = v9fs_vfs_mkdir,
 	.rmdir = v9fs_vfs_rmdir,

include/net/9p/9p.h

@@ -88,6 +88,8 @@ do { \
  * enum p9_msg_t - 9P message types
  * @P9_TSTATFS: file system status request
  * @P9_RSTATFS: file system status response
+ * @P9_TSYMLINK: make symlink request
+ * @P9_RSYMLINK: make symlink response
  * @P9_TRENAME: rename request
  * @P9_RRENAME: rename response
  * @P9_TVERSION: version handshake request
@@ -131,6 +133,8 @@ do { \
 enum p9_msg_t {
 	P9_TSTATFS = 8,
 	P9_RSTATFS,
+	P9_TSYMLINK = 16,
+	P9_RSYMLINK,
 	P9_TRENAME = 20,
 	P9_RRENAME,
 	P9_TGETATTR = 24,

include/net/9p/client.h

@@ -227,6 +227,8 @@ 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_symlink(struct p9_fid *fid, char *name, char *symname, gid_t gid,
+							struct p9_qid *qid);
 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 +1095,40 @@ int p9_client_fcreate(struct p9_fid *fid, char *name, u32 perm, int mode,
 }
 EXPORT_SYMBOL(p9_client_fcreate);
 
+int p9_client_symlink(struct p9_fid *dfid, char *name, char *symtgt, gid_t gid,
+		struct p9_qid *qid)
+{
+	int err = 0;
+	struct p9_client *clnt;
+	struct p9_req_t *req;
+
+	P9_DPRINTK(P9_DEBUG_9P, ">>> TSYMLINK dfid %d name %s  symtgt %s\n",
+			dfid->fid, name, symtgt);
+	clnt = dfid->clnt;
+
+	req = p9_client_rpc(clnt, P9_TSYMLINK, "dssd", dfid->fid, name, symtgt,
+			gid);
+	if (IS_ERR(req)) {
+		err = PTR_ERR(req);
+		goto error;
+	}
+
+	err = p9pdu_readf(req->rc, clnt->proto_version, "Q", qid);
+	if (err) {
+		p9pdu_dump(1, req->rc);
+		goto free_and_error;
+	}
+
+	P9_DPRINTK(P9_DEBUG_9P, "<<< RSYMLINK qid %x.%llx.%x\n",
+			qid->type, (unsigned long long)qid->path, qid->version);
+
+free_and_error:
+	p9_free_req(clnt, req);
+error:
+	return err;
+}
+EXPORT_SYMBOL(p9_client_symlink);
+
 int p9_client_link(struct p9_fid *dfid, struct p9_fid *oldfid, char *newname)
 {
 	struct p9_client *clnt;