wrappers for ->i_mutex access

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index f4617cf..781c139 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -795,7 +795,7 @@
 
 	ro = mnt_want_write(mnt);	/* we'll drop it in any case */
 	error = 0;
-	mutex_lock(&d_inode(root)->i_mutex);
+	inode_lock(d_inode(root));
 	path.dentry = lookup_one_len(name->name, root, strlen(name->name));
 	if (IS_ERR(path.dentry)) {
 		error = PTR_ERR(path.dentry);
@@ -841,7 +841,7 @@
 		put_unused_fd(fd);
 		fd = error;
 	}
-	mutex_unlock(&d_inode(root)->i_mutex);
+	inode_unlock(d_inode(root));
 	if (!ro)
 		mnt_drop_write(mnt);
 out_putname:
@@ -866,7 +866,7 @@
 	err = mnt_want_write(mnt);
 	if (err)
 		goto out_name;
-	mutex_lock_nested(&d_inode(mnt->mnt_root)->i_mutex, I_MUTEX_PARENT);
+	inode_lock_nested(d_inode(mnt->mnt_root), I_MUTEX_PARENT);
 	dentry = lookup_one_len(name->name, mnt->mnt_root,
 				strlen(name->name));
 	if (IS_ERR(dentry)) {
@@ -884,7 +884,7 @@
 	dput(dentry);
 
 out_unlock:
-	mutex_unlock(&d_inode(mnt->mnt_root)->i_mutex);
+	inode_unlock(d_inode(mnt->mnt_root));
 	if (inode)
 		iput(inode);
 	mnt_drop_write(mnt);