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/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index caba848..c6ced4c 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -436,7 +436,7 @@
 		rc = -ENOMEM;
 		goto out;
 	}
-	mutex_lock(&lower_inode->i_mutex);
+	inode_lock(lower_inode);
 	size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 					   xattr_virt, PAGE_CACHE_SIZE);
 	if (size < 0)
@@ -444,7 +444,7 @@
 	put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 	rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 					 xattr_virt, size, 0);
-	mutex_unlock(&lower_inode->i_mutex);
+	inode_unlock(lower_inode);
 	if (rc)
 		printk(KERN_ERR "Error whilst attempting to write inode size "
 		       "to lower file xattr; rc = [%d]\n", rc);