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Commit ba0268a8 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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SLUB: accurately compare debug flags during slab cache merge 

This was posted on Aug 28 and fixes an issue that could cause troubles
when slab caches >=128k are created.

http://marc.info/?l=linux-mm&m=118798149918424&w=2



Currently we simply add the debug flags unconditional when checking for a
matching slab.  This creates issues for sysfs processing when slabs exist
that are exempt from debugging due to their huge size or because only a
subset of slabs was selected for debugging.

We need to only add the flags if kmem_cache_open() would also add them.

Create a function to calculate the flags that would be set
if the cache would be opened and use that function to determine
the flags before looking for a compatible slab.

[akpm@linux-foundation.org: fixlets]
Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4150d3f5

mm/slub.c

+23 −15
Original line number Diff line number Diff line
@@ -986,7 +986,9 @@ static int __init setup_slub_debug(char *str) 


__setup("slub_debug", setup_slub_debug);



static void kmem_cache_open_debug_check(struct kmem_cache *s)

static unsigned long kmem_cache_flags(unsigned long objsize,

	unsigned long flags, const char *name,

	void (*ctor)(void *, struct kmem_cache *, unsigned long))

{

	/*

	 * The page->offset field is only 16 bit wide. This is an offset
@@ -1000,19 +1002,21 @@ static void kmem_cache_open_debug_check(struct kmem_cache *s) 
	 * Debugging or ctor may create a need to move the free

	 * pointer. Fail if this happens.

	 */

	if (s->objsize >= 65535 * sizeof(void *)) {

		BUG_ON(s->flags & (SLAB_RED_ZONE | SLAB_POISON |

	if (objsize >= 65535 * sizeof(void *)) {

		BUG_ON(flags & (SLAB_RED_ZONE | SLAB_POISON |

				SLAB_STORE_USER | SLAB_DESTROY_BY_RCU));

		BUG_ON(s->ctor);

	}

	else

		BUG_ON(ctor);

	} else {

		/*

		 * Enable debugging if selected on the kernel commandline.

		 */

		if (slub_debug && (!slub_debug_slabs ||

		    strncmp(slub_debug_slabs, s->name,

		    strncmp(slub_debug_slabs, name,

		    	strlen(slub_debug_slabs)) == 0))

				s->flags |= slub_debug;

				flags |= slub_debug;

	}



	return flags;

}

#else

static inline void setup_object_debug(struct kmem_cache *s,
@@ -1029,7 +1033,12 @@ static inline int slab_pad_check(struct kmem_cache *s, struct page *page) 
static inline int check_object(struct kmem_cache *s, struct page *page,

			void *object, int active) { return 1; }

static inline void add_full(struct kmem_cache_node *n, struct page *page) {}

static inline void kmem_cache_open_debug_check(struct kmem_cache *s) {}

static inline unsigned long kmem_cache_flags(unsigned long objsize,

	unsigned long flags, const char *name,

	void (*ctor)(void *, struct kmem_cache *, unsigned long))

{

	return flags;

}

#define slub_debug 0

#endif

/*
@@ -2088,9 +2097,8 @@ static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags, 
	s->name = name;

	s->ctor = ctor;

	s->objsize = size;

	s->flags = flags;

	s->align = align;

	kmem_cache_open_debug_check(s);

	s->flags = kmem_cache_flags(size, flags, name, ctor);



	if (!calculate_sizes(s))

		goto error;
@@ -2660,7 +2668,7 @@ static int slab_unmergeable(struct kmem_cache *s) 
}



static struct kmem_cache *find_mergeable(size_t size,

		size_t align, unsigned long flags,

		size_t align, unsigned long flags, const char *name,

		void (*ctor)(void *, struct kmem_cache *, unsigned long))

{

	struct kmem_cache *s;
@@ -2674,6 +2682,7 @@ static struct kmem_cache *find_mergeable(size_t size, 
	size = ALIGN(size, sizeof(void *));

	align = calculate_alignment(flags, align, size);

	size = ALIGN(size, align);

	flags = kmem_cache_flags(size, flags, name, NULL);



	list_for_each_entry(s, &slab_caches, list) {

		if (slab_unmergeable(s))
@@ -2682,8 +2691,7 @@ static struct kmem_cache *find_mergeable(size_t size, 
		if (size > s->size)

			continue;



		if (((flags | slub_debug) & SLUB_MERGE_SAME) !=

			(s->flags & SLUB_MERGE_SAME))

		if ((flags & SLUB_MERGE_SAME) != (s->flags & SLUB_MERGE_SAME))

				continue;

		/*

		 * Check if alignment is compatible.
@@ -2707,7 +2715,7 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size, 
	struct kmem_cache *s;



	down_write(&slub_lock);

	s = find_mergeable(size, align, flags, ctor);

	s = find_mergeable(size, align, flags, name, ctor);

	if (s) {

		s->refcount++;

		/*