Commit 3de47213 authored by David Rientjes's avatar David Rientjes Committed by Pekka Enberg
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slub: use size and objsize orders to disable debug flags 



This patch moves the masking of debugging flags which increase a cache's
min order due to metadata when `slub_debug=O' is used from
kmem_cache_flags() to kmem_cache_open().

Instead of defining the maximum metadata size increase in a preprocessor
macro, this approach uses the cache's ->size and ->objsize members to
determine if the min order increased due to debugging options.  If so,
the flags specified in the more appropriately named DEBUG_METADATA_FLAGS
are masked off.

This approach was suggested by Christoph Lameter
<cl@linux-foundation.org>.

Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
parent fa5ec8a1

mm/slub.c

+19 −21
Original line number Diff line number Diff line
@@ -142,11 +142,11 @@ 
				SLAB_POISON | SLAB_STORE_USER)



/*

 * Debugging flags that require metadata to be stored in the slab, up to

 * DEBUG_SIZE in size.

 * Debugging flags that require metadata to be stored in the slab.  These get

 * disabled when slub_debug=O is used and a cache's min order increases with

 * metadata.

 */

#define DEBUG_SIZE_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)

#define DEBUG_SIZE (3 * sizeof(void *) + 2 * sizeof(struct track))

#define DEBUG_METADATA_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)



/*

 * Set of flags that will prevent slab merging
@@ -1040,27 +1040,13 @@ static unsigned long kmem_cache_flags(unsigned long objsize, 
	unsigned long flags, const char *name,

	void (*ctor)(void *))

{

	int debug_flags = slub_debug;



	/*

	 * Enable debugging if selected on the kernel commandline.

	 */

	if (debug_flags) {

		if (slub_debug_slabs &&

		    strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)))

			goto out;

	if (slub_debug && (!slub_debug_slabs ||

		!strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs))))

		flags |= slub_debug;



		/*

		 * Disable debugging that increases slab size if the minimum

		 * slab order would have increased as a result.

		 */

		if (disable_higher_order_debug &&

		    get_order(objsize + DEBUG_SIZE) > get_order(objsize))

			debug_flags &= ~DEBUG_SIZE_FLAGS;



		flags |= debug_flags;

	}

out:

	return flags;

}

#else
@@ -2488,6 +2474,18 @@ static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags, 


	if (!calculate_sizes(s, -1))

		goto error;

	if (disable_higher_order_debug) {

		/*

		 * Disable debugging flags that store metadata if the min slab

		 * order increased.

		 */

		if (get_order(s->size) > get_order(s->objsize)) {

			s->flags &= ~DEBUG_METADATA_FLAGS;

			s->offset = 0;

			if (!calculate_sizes(s, -1))

				goto error;

		}

	}



	/*

	 * The larger the object size is, the more pages we want on the partial

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