ext4: hole-punch use truncate_pagecache_range

When truncating a file, we unmap pages from userspace first, as that's
usually more efficient than relying, page by page, on the fallback in
truncate_inode_page() - particularly if the file is mapped many times.

Do the same when punching a hole: 3.4 added truncate_pagecache_range()
to do the unmap and trunc, so use it in ext4_ext_punch_hole(), instead
of calling truncate_inode_pages_range() directly.
Signed-off-by: NHugh Dickins <hughd@google.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/extents.c

@@ -4789,8 +4789,8 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 
 	/* Now release the pages */
 	if (last_page_offset > first_page_offset) {
-		truncate_inode_pages_range(mapping, first_page_offset,
-					   last_page_offset-1);
+		truncate_pagecache_range(inode, first_page_offset,
+					 last_page_offset - 1);
 	}
 
 	/* finish any pending end_io work */