9p: Implement TREADLINK operation for 9p2000.L

Synopsis

	size[4] TReadlink tag[2] fid[4]
	size[4] RReadlink tag[2] target[s]

Description
	Readlink is used to return the contents of the symoblic link
        referred by fid. Contents of symboic link is returned as a
        response.

	target[s] - Contents of the symbolic link referred by fid.

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Reviewed-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>

4 files changed, 86 insertions, 3 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 68f02973c338..88419073c654 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -1527,7 +1527,7 @@ static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
         if (IS_ERR(fid))
                 return PTR_ERR(fid);
 
-        if (!v9fs_proto_dotu(v9ses) && !v9fs_proto_dotl(v9ses))
+        if (!v9fs_proto_dotu(v9ses))
                 return -EBADF;
 
         st = p9_client_stat(fid);
@@ -1995,6 +1995,60 @@ error:
         return err;
 }
 
+static int
+v9fs_vfs_readlink_dotl(struct dentry *dentry, char *buffer, int buflen)
+{
+        int retval;
+        struct p9_fid *fid;
+        char *target = NULL;
+
+        P9_DPRINTK(P9_DEBUG_VFS, " %s\n", dentry->d_name.name);
+        retval = -EPERM;
+        fid = v9fs_fid_lookup(dentry);
+        if (IS_ERR(fid))
+                return PTR_ERR(fid);
+
+        retval = p9_client_readlink(fid, &target);
+        if (retval < 0)
+                return retval;
+
+        strncpy(buffer, target, buflen);
+        P9_DPRINTK(P9_DEBUG_VFS, "%s -> %s\n", dentry->d_name.name, buffer);
+
+        retval = strnlen(buffer, buflen);
+        return retval;
+}
+
+/**
+ * v9fs_vfs_follow_link_dotl - follow a symlink path
+ * @dentry: dentry for symlink
+ * @nd: nameidata
+ *
+ */
+
+static void *
+v9fs_vfs_follow_link_dotl(struct dentry *dentry, struct nameidata *nd)
+{
+        int len = 0;
+        char *link = __getname();
+
+        P9_DPRINTK(P9_DEBUG_VFS, "%s n", dentry->d_name.name);
+
+        if (!link)
+                link = ERR_PTR(-ENOMEM);
+        else {
+                len = v9fs_vfs_readlink_dotl(dentry, link, PATH_MAX);
+                if (len < 0) {
+                        __putname(link);
+                        link = ERR_PTR(len);
+                } else
+                        link[min(len, PATH_MAX-1)] = 0;
+        }
+        nd_set_link(nd, link);
+
+        return NULL;
+}
+
 static const struct inode_operations v9fs_dir_inode_operations_dotu = {
         .create = v9fs_vfs_create,
         .lookup = v9fs_vfs_lookup,
@@ -2064,8 +2118,8 @@ static const struct inode_operations v9fs_symlink_inode_operations = {
 };
 
 static const struct inode_operations v9fs_symlink_inode_operations_dotl = {
-        .readlink = generic_readlink,
-        .follow_link = v9fs_vfs_follow_link,
+        .readlink = v9fs_vfs_readlink_dotl,
+        .follow_link = v9fs_vfs_follow_link_dotl,
         .put_link = v9fs_vfs_put_link,
         .getattr = v9fs_vfs_getattr_dotl,
         .setattr = v9fs_vfs_setattr_dotl,
diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index 6367a71d84fc..071fd7a8d781 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -153,6 +153,8 @@ enum p9_msg_t {
         P9_RMKNOD,
         P9_TRENAME = 20,
         P9_RRENAME,
+        P9_TREADLINK = 22,
+        P9_RREADLINK,
         P9_TGETATTR = 24,
         P9_RGETATTR,
         P9_TSETATTR = 26,
diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index 127c9f2a9cb8..335b088e7672 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -262,5 +262,6 @@ int p9_is_proto_dotu(struct p9_client *clnt);
 int p9_is_proto_dotl(struct p9_client *clnt);
 struct p9_fid *p9_client_xattrwalk(struct p9_fid *, const char *, u64 *);
 int p9_client_xattrcreate(struct p9_fid *, const char *, u64, int);
+int p9_client_readlink(struct p9_fid *fid, char **target);
 
 #endif /* NET_9P_CLIENT_H */
diff --git a/net/9p/client.c b/net/9p/client.c
index fc1b0579016a..2bc99e9031e7 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1870,3 +1870,29 @@ error:
         return err;
 }
 EXPORT_SYMBOL(p9_client_getlock_dotl);
+
+int p9_client_readlink(struct p9_fid *fid, char **target)
+{
+        int err;
+        struct p9_client *clnt;
+        struct p9_req_t *req;
+
+        err = 0;
+        clnt = fid->clnt;
+        P9_DPRINTK(P9_DEBUG_9P, ">>> TREADLINK fid %d\n", fid->fid);
+
+        req = p9_client_rpc(clnt, P9_TREADLINK, "d", fid->fid);
+        if (IS_ERR(req))
+                return PTR_ERR(req);
+
+        err = p9pdu_readf(req->rc, clnt->proto_version, "s", target);
+        if (err) {
+                p9pdu_dump(1, req->rc);
+                goto error;
+        }
+        P9_DPRINTK(P9_DEBUG_9P, "<<< RREADLINK target %s\n", *target);
+error:
+        p9_free_req(clnt, req);
+        return err;
+}
+EXPORT_SYMBOL(p9_client_readlink);