mm: optimize acorn partition truncate

invalidate_bdev() is superfluous when truncate_inode_pages() is also
called.  do call invalidate_bh_lrus() though, to avoid stale pointers.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/partitions/acorn.c

@@ -271,7 +271,7 @@ adfspart_check_ADFS(struct parsed_partitions *state, struct block_device *bdev)
 		extern void xd_set_geometry(struct block_device *,
 			unsigned char, unsigned char, unsigned int);
 		xd_set_geometry(bdev, dr->secspertrack, heads, 1);
-		invalidate_bdev(bdev);
+		invalidate_bh_lrus();
 		truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
 	}
 #endif