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/overlayfs/super.c b/fs/overlayfs/super.c
index d250604..8d826bd 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -229,7 +229,7 @@
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
 
-	WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
+	WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
 	WARN_ON(oe->__upperdentry);
 	BUG_ON(!upperdentry->d_inode);
 	/*
@@ -244,7 +244,7 @@
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
 
-	WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+	WARN_ON(!inode_is_locked(dentry->d_inode));
 	oe->version++;
 }
 
@@ -252,7 +252,7 @@
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
 
-	WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+	WARN_ON(!inode_is_locked(dentry->d_inode));
 	return oe->version;
 }
 
@@ -375,9 +375,9 @@
 {
 	struct dentry *dentry;
 
-	mutex_lock(&dir->d_inode->i_mutex);
+	inode_lock(dir->d_inode);
 	dentry = lookup_one_len(name->name, dir, name->len);
-	mutex_unlock(&dir->d_inode->i_mutex);
+	inode_unlock(dir->d_inode);
 
 	if (IS_ERR(dentry)) {
 		if (PTR_ERR(dentry) == -ENOENT)
@@ -744,7 +744,7 @@
 	if (err)
 		return ERR_PTR(err);
 
-	mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
+	inode_lock_nested(dir, I_MUTEX_PARENT);
 retry:
 	work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
 			      strlen(OVL_WORKDIR_NAME));
@@ -770,7 +770,7 @@
 			goto out_dput;
 	}
 out_unlock:
-	mutex_unlock(&dir->i_mutex);
+	inode_unlock(dir);
 	mnt_drop_write(mnt);
 
 	return work;