Commit 9888e6fa authored by Linus Torvalds's avatar Linus Torvalds
Browse files

slab: clarify and fix calculate_slab_order() 



If we triggered the 'offslab_limit' test, we would return with
cachep->gfporder incremented once too many times.

This clarifies the logic somewhat, and fixes that bug.

Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f716d830

mm/slab.c

+12 −12
Original line number Diff line number Diff line
@@ -1628,36 +1628,36 @@ static inline size_t calculate_slab_order(struct kmem_cache *cachep, 
			size_t size, size_t align, unsigned long flags)

{

	size_t left_over = 0;

	int gfporder;



	for (;; cachep->gfporder++) {

	for (gfporder = 0 ; gfporder <= MAX_GFP_ORDER; gfporder++) {

		unsigned int num;

		size_t remainder;



		if (cachep->gfporder > MAX_GFP_ORDER) {

			cachep->num = 0;

			break;

		}



		cache_estimate(cachep->gfporder, size, align, flags,

			       &remainder, &num);

		cache_estimate(gfporder, size, align, flags, &remainder, &num);

		if (!num)

			continue;



		/* More than offslab_limit objects will cause problems */

		if (flags & CFLGS_OFF_SLAB && cachep->num > offslab_limit)

		if ((flags & CFLGS_OFF_SLAB) && num > offslab_limit)

			break;



		/* Found something acceptable - save it away */

		cachep->num = num;

		cachep->gfporder = gfporder;

		left_over = remainder;



		/*

		 * Large number of objects is good, but very large slabs are

		 * currently bad for the gfp()s.

		 */

		if (cachep->gfporder >= slab_break_gfp_order)

		if (gfporder >= slab_break_gfp_order)

			break;



		if ((left_over * 8) <= (PAGE_SIZE << cachep->gfporder))

			/* Acceptable internal fragmentation */

		/*

		 * Acceptable internal fragmentation?

		 */

		if ((left_over * 8) <= (PAGE_SIZE << gfporder))

			break;

	}

	return left_over;