Revert "SLUB: remove useless masking of GFP_ZERO"

This reverts commit 3811dbf67162bd08412f1b0e02e554f353e93bdb.

The masking was not at all useless, and it was sensible.  We handle
GFP_ZERO in the caller, and passing it down to any page allocator logic
is buggy and wrong.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slub.c b/mm/slub.c
index b72bc98..84ed734 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1470,6 +1470,9 @@
 	void **object;
 	struct page *new;
 
+	/* We handle __GFP_ZERO in the caller */
+	gfpflags &= ~__GFP_ZERO;
+
 	if (!c->page)
 		goto new_slab;