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/ext4/file.c b/fs/ext4/file.c
index 749b222..8eb87e3 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -113,7 +113,7 @@
 		ext4_unwritten_wait(inode);
 	}
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 	ret = generic_write_checks(iocb, from);
 	if (ret <= 0)
 		goto out;
@@ -169,7 +169,7 @@
 	}
 
 	ret = __generic_file_write_iter(iocb, from);
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 
 	if (ret > 0) {
 		ssize_t err;
@@ -186,7 +186,7 @@
 	return ret;
 
 out:
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 	if (aio_mutex)
 		mutex_unlock(aio_mutex);
 	return ret;
@@ -561,11 +561,11 @@
 	int blkbits;
 	int ret = 0;
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 
 	isize = i_size_read(inode);
 	if (offset >= isize) {
-		mutex_unlock(&inode->i_mutex);
+		inode_unlock(inode);
 		return -ENXIO;
 	}
 
@@ -613,7 +613,7 @@
 		dataoff = (loff_t)last << blkbits;
 	} while (last <= end);
 
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 
 	if (dataoff > isize)
 		return -ENXIO;
@@ -634,11 +634,11 @@
 	int blkbits;
 	int ret = 0;
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 
 	isize = i_size_read(inode);
 	if (offset >= isize) {
-		mutex_unlock(&inode->i_mutex);
+		inode_unlock(inode);
 		return -ENXIO;
 	}
 
@@ -689,7 +689,7 @@
 		break;
 	} while (last <= end);
 
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 
 	if (holeoff > isize)
 		holeoff = isize;