truncate: drop 'oldsize' truncate_pagecache() parameter

truncate_pagecache() doesn't care about old size since commit
cedabed49b39 ("vfs: Fix vmtruncate() regression").  Let's drop it.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index b21a3cd..256d959 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -221,12 +221,10 @@
 				    struct btrfs_path *path,
 				    struct inode *inode)
 {
-	loff_t oldsize;
 	int ret = 0;
 
-	oldsize = i_size_read(inode);
 	btrfs_i_size_write(inode, 0);
-	truncate_pagecache(inode, oldsize, 0);
+	truncate_pagecache(inode, 0);
 
 	/*
 	 * We don't need an orphan item because truncating the free space cache