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v3.1
  1/*
  2 * SLOB Allocator: Simple List Of Blocks
  3 *
  4 * Matt Mackall <mpm@selenic.com> 12/30/03
  5 *
  6 * NUMA support by Paul Mundt, 2007.
  7 *
  8 * How SLOB works:
  9 *
 10 * The core of SLOB is a traditional K&R style heap allocator, with
 11 * support for returning aligned objects. The granularity of this
 12 * allocator is as little as 2 bytes, however typically most architectures
 13 * will require 4 bytes on 32-bit and 8 bytes on 64-bit.
 14 *
 15 * The slob heap is a set of linked list of pages from alloc_pages(),
 16 * and within each page, there is a singly-linked list of free blocks
 17 * (slob_t). The heap is grown on demand. To reduce fragmentation,
 18 * heap pages are segregated into three lists, with objects less than
 19 * 256 bytes, objects less than 1024 bytes, and all other objects.
 20 *
 21 * Allocation from heap involves first searching for a page with
 22 * sufficient free blocks (using a next-fit-like approach) followed by
 23 * a first-fit scan of the page. Deallocation inserts objects back
 24 * into the free list in address order, so this is effectively an
 25 * address-ordered first fit.
 26 *
 27 * Above this is an implementation of kmalloc/kfree. Blocks returned
 28 * from kmalloc are prepended with a 4-byte header with the kmalloc size.
 29 * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
 30 * alloc_pages() directly, allocating compound pages so the page order
 31 * does not have to be separately tracked, and also stores the exact
 32 * allocation size in page->private so that it can be used to accurately
 33 * provide ksize(). These objects are detected in kfree() because slob_page()
 34 * is false for them.
 35 *
 36 * SLAB is emulated on top of SLOB by simply calling constructors and
 37 * destructors for every SLAB allocation. Objects are returned with the
 38 * 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which
 39 * case the low-level allocator will fragment blocks to create the proper
 40 * alignment. Again, objects of page-size or greater are allocated by
 41 * calling alloc_pages(). As SLAB objects know their size, no separate
 42 * size bookkeeping is necessary and there is essentially no allocation
 43 * space overhead, and compound pages aren't needed for multi-page
 44 * allocations.
 45 *
 46 * NUMA support in SLOB is fairly simplistic, pushing most of the real
 47 * logic down to the page allocator, and simply doing the node accounting
 48 * on the upper levels. In the event that a node id is explicitly
 49 * provided, alloc_pages_exact_node() with the specified node id is used
 50 * instead. The common case (or when the node id isn't explicitly provided)
 51 * will default to the current node, as per numa_node_id().
 52 *
 53 * Node aware pages are still inserted in to the global freelist, and
 54 * these are scanned for by matching against the node id encoded in the
 55 * page flags. As a result, block allocations that can be satisfied from
 56 * the freelist will only be done so on pages residing on the same node,
 57 * in order to prevent random node placement.
 58 */
 59
 60#include <linux/kernel.h>
 61#include <linux/slab.h>
 
 62#include <linux/mm.h>
 63#include <linux/swap.h> /* struct reclaim_state */
 64#include <linux/cache.h>
 65#include <linux/init.h>
 66#include <linux/module.h>
 67#include <linux/rcupdate.h>
 68#include <linux/list.h>
 69#include <linux/kmemleak.h>
 70
 71#include <trace/events/kmem.h>
 72
 73#include <linux/atomic.h>
 74
 
 75/*
 76 * slob_block has a field 'units', which indicates size of block if +ve,
 77 * or offset of next block if -ve (in SLOB_UNITs).
 78 *
 79 * Free blocks of size 1 unit simply contain the offset of the next block.
 80 * Those with larger size contain their size in the first SLOB_UNIT of
 81 * memory, and the offset of the next free block in the second SLOB_UNIT.
 82 */
 83#if PAGE_SIZE <= (32767 * 2)
 84typedef s16 slobidx_t;
 85#else
 86typedef s32 slobidx_t;
 87#endif
 88
 89struct slob_block {
 90	slobidx_t units;
 91};
 92typedef struct slob_block slob_t;
 93
 94/*
 95 * We use struct page fields to manage some slob allocation aspects,
 96 * however to avoid the horrible mess in include/linux/mm_types.h, we'll
 97 * just define our own struct page type variant here.
 98 */
 99struct slob_page {
100	union {
101		struct {
102			unsigned long flags;	/* mandatory */
103			atomic_t _count;	/* mandatory */
104			slobidx_t units;	/* free units left in page */
105			unsigned long pad[2];
106			slob_t *free;		/* first free slob_t in page */
107			struct list_head list;	/* linked list of free pages */
108		};
109		struct page page;
110	};
111};
112static inline void struct_slob_page_wrong_size(void)
113{ BUILD_BUG_ON(sizeof(struct slob_page) != sizeof(struct page)); }
114
115/*
116 * free_slob_page: call before a slob_page is returned to the page allocator.
117 */
118static inline void free_slob_page(struct slob_page *sp)
119{
120	reset_page_mapcount(&sp->page);
121	sp->page.mapping = NULL;
122}
123
124/*
125 * All partially free slob pages go on these lists.
126 */
127#define SLOB_BREAK1 256
128#define SLOB_BREAK2 1024
129static LIST_HEAD(free_slob_small);
130static LIST_HEAD(free_slob_medium);
131static LIST_HEAD(free_slob_large);
132
133/*
134 * is_slob_page: True for all slob pages (false for bigblock pages)
135 */
136static inline int is_slob_page(struct slob_page *sp)
137{
138	return PageSlab((struct page *)sp);
139}
140
141static inline void set_slob_page(struct slob_page *sp)
142{
143	__SetPageSlab((struct page *)sp);
144}
145
146static inline void clear_slob_page(struct slob_page *sp)
147{
148	__ClearPageSlab((struct page *)sp);
149}
150
151static inline struct slob_page *slob_page(const void *addr)
152{
153	return (struct slob_page *)virt_to_page(addr);
154}
155
156/*
157 * slob_page_free: true for pages on free_slob_pages list.
158 */
159static inline int slob_page_free(struct slob_page *sp)
160{
161	return PageSlobFree((struct page *)sp);
162}
163
164static void set_slob_page_free(struct slob_page *sp, struct list_head *list)
165{
166	list_add(&sp->list, list);
167	__SetPageSlobFree((struct page *)sp);
168}
169
170static inline void clear_slob_page_free(struct slob_page *sp)
171{
172	list_del(&sp->list);
173	__ClearPageSlobFree((struct page *)sp);
174}
175
176#define SLOB_UNIT sizeof(slob_t)
177#define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
178#define SLOB_ALIGN L1_CACHE_BYTES
179
180/*
181 * struct slob_rcu is inserted at the tail of allocated slob blocks, which
182 * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
183 * the block using call_rcu.
184 */
185struct slob_rcu {
186	struct rcu_head head;
187	int size;
188};
189
190/*
191 * slob_lock protects all slob allocator structures.
192 */
193static DEFINE_SPINLOCK(slob_lock);
194
195/*
196 * Encode the given size and next info into a free slob block s.
197 */
198static void set_slob(slob_t *s, slobidx_t size, slob_t *next)
199{
200	slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
201	slobidx_t offset = next - base;
202
203	if (size > 1) {
204		s[0].units = size;
205		s[1].units = offset;
206	} else
207		s[0].units = -offset;
208}
209
210/*
211 * Return the size of a slob block.
212 */
213static slobidx_t slob_units(slob_t *s)
214{
215	if (s->units > 0)
216		return s->units;
217	return 1;
218}
219
220/*
221 * Return the next free slob block pointer after this one.
222 */
223static slob_t *slob_next(slob_t *s)
224{
225	slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
226	slobidx_t next;
227
228	if (s[0].units < 0)
229		next = -s[0].units;
230	else
231		next = s[1].units;
232	return base+next;
233}
234
235/*
236 * Returns true if s is the last free block in its page.
237 */
238static int slob_last(slob_t *s)
239{
240	return !((unsigned long)slob_next(s) & ~PAGE_MASK);
241}
242
243static void *slob_new_pages(gfp_t gfp, int order, int node)
244{
245	void *page;
246
247#ifdef CONFIG_NUMA
248	if (node != -1)
249		page = alloc_pages_exact_node(node, gfp, order);
250	else
251#endif
252		page = alloc_pages(gfp, order);
253
254	if (!page)
255		return NULL;
256
257	return page_address(page);
258}
259
260static void slob_free_pages(void *b, int order)
261{
262	if (current->reclaim_state)
263		current->reclaim_state->reclaimed_slab += 1 << order;
264	free_pages((unsigned long)b, order);
265}
266
267/*
268 * Allocate a slob block within a given slob_page sp.
269 */
270static void *slob_page_alloc(struct slob_page *sp, size_t size, int align)
271{
272	slob_t *prev, *cur, *aligned = NULL;
273	int delta = 0, units = SLOB_UNITS(size);
274
275	for (prev = NULL, cur = sp->free; ; prev = cur, cur = slob_next(cur)) {
276		slobidx_t avail = slob_units(cur);
277
278		if (align) {
279			aligned = (slob_t *)ALIGN((unsigned long)cur, align);
280			delta = aligned - cur;
281		}
282		if (avail >= units + delta) { /* room enough? */
283			slob_t *next;
284
285			if (delta) { /* need to fragment head to align? */
286				next = slob_next(cur);
287				set_slob(aligned, avail - delta, next);
288				set_slob(cur, delta, aligned);
289				prev = cur;
290				cur = aligned;
291				avail = slob_units(cur);
292			}
293
294			next = slob_next(cur);
295			if (avail == units) { /* exact fit? unlink. */
296				if (prev)
297					set_slob(prev, slob_units(prev), next);
298				else
299					sp->free = next;
300			} else { /* fragment */
301				if (prev)
302					set_slob(prev, slob_units(prev), cur + units);
303				else
304					sp->free = cur + units;
305				set_slob(cur + units, avail - units, next);
306			}
307
308			sp->units -= units;
309			if (!sp->units)
310				clear_slob_page_free(sp);
311			return cur;
312		}
313		if (slob_last(cur))
314			return NULL;
315	}
316}
317
318/*
319 * slob_alloc: entry point into the slob allocator.
320 */
321static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
322{
323	struct slob_page *sp;
324	struct list_head *prev;
325	struct list_head *slob_list;
326	slob_t *b = NULL;
327	unsigned long flags;
328
329	if (size < SLOB_BREAK1)
330		slob_list = &free_slob_small;
331	else if (size < SLOB_BREAK2)
332		slob_list = &free_slob_medium;
333	else
334		slob_list = &free_slob_large;
335
336	spin_lock_irqsave(&slob_lock, flags);
337	/* Iterate through each partially free page, try to find room */
338	list_for_each_entry(sp, slob_list, list) {
339#ifdef CONFIG_NUMA
340		/*
341		 * If there's a node specification, search for a partial
342		 * page with a matching node id in the freelist.
343		 */
344		if (node != -1 && page_to_nid(&sp->page) != node)
345			continue;
346#endif
347		/* Enough room on this page? */
348		if (sp->units < SLOB_UNITS(size))
349			continue;
350
351		/* Attempt to alloc */
352		prev = sp->list.prev;
353		b = slob_page_alloc(sp, size, align);
354		if (!b)
355			continue;
356
357		/* Improve fragment distribution and reduce our average
358		 * search time by starting our next search here. (see
359		 * Knuth vol 1, sec 2.5, pg 449) */
360		if (prev != slob_list->prev &&
361				slob_list->next != prev->next)
362			list_move_tail(slob_list, prev->next);
363		break;
364	}
365	spin_unlock_irqrestore(&slob_lock, flags);
366
367	/* Not enough space: must allocate a new page */
368	if (!b) {
369		b = slob_new_pages(gfp & ~__GFP_ZERO, 0, node);
370		if (!b)
371			return NULL;
372		sp = slob_page(b);
373		set_slob_page(sp);
374
375		spin_lock_irqsave(&slob_lock, flags);
376		sp->units = SLOB_UNITS(PAGE_SIZE);
377		sp->free = b;
378		INIT_LIST_HEAD(&sp->list);
379		set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
380		set_slob_page_free(sp, slob_list);
381		b = slob_page_alloc(sp, size, align);
382		BUG_ON(!b);
383		spin_unlock_irqrestore(&slob_lock, flags);
384	}
385	if (unlikely((gfp & __GFP_ZERO) && b))
386		memset(b, 0, size);
387	return b;
388}
389
390/*
391 * slob_free: entry point into the slob allocator.
392 */
393static void slob_free(void *block, int size)
394{
395	struct slob_page *sp;
396	slob_t *prev, *next, *b = (slob_t *)block;
397	slobidx_t units;
398	unsigned long flags;
399	struct list_head *slob_list;
400
401	if (unlikely(ZERO_OR_NULL_PTR(block)))
402		return;
403	BUG_ON(!size);
404
405	sp = slob_page(block);
406	units = SLOB_UNITS(size);
407
408	spin_lock_irqsave(&slob_lock, flags);
409
410	if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {
411		/* Go directly to page allocator. Do not pass slob allocator */
412		if (slob_page_free(sp))
413			clear_slob_page_free(sp);
414		spin_unlock_irqrestore(&slob_lock, flags);
415		clear_slob_page(sp);
416		free_slob_page(sp);
417		slob_free_pages(b, 0);
418		return;
419	}
420
421	if (!slob_page_free(sp)) {
422		/* This slob page is about to become partially free. Easy! */
423		sp->units = units;
424		sp->free = b;
425		set_slob(b, units,
426			(void *)((unsigned long)(b +
427					SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
428		if (size < SLOB_BREAK1)
429			slob_list = &free_slob_small;
430		else if (size < SLOB_BREAK2)
431			slob_list = &free_slob_medium;
432		else
433			slob_list = &free_slob_large;
434		set_slob_page_free(sp, slob_list);
435		goto out;
436	}
437
438	/*
439	 * Otherwise the page is already partially free, so find reinsertion
440	 * point.
441	 */
442	sp->units += units;
443
444	if (b < sp->free) {
445		if (b + units == sp->free) {
446			units += slob_units(sp->free);
447			sp->free = slob_next(sp->free);
448		}
449		set_slob(b, units, sp->free);
450		sp->free = b;
451	} else {
452		prev = sp->free;
453		next = slob_next(prev);
454		while (b > next) {
455			prev = next;
456			next = slob_next(prev);
457		}
458
459		if (!slob_last(prev) && b + units == next) {
460			units += slob_units(next);
461			set_slob(b, units, slob_next(next));
462		} else
463			set_slob(b, units, next);
464
465		if (prev + slob_units(prev) == b) {
466			units = slob_units(b) + slob_units(prev);
467			set_slob(prev, units, slob_next(b));
468		} else
469			set_slob(prev, slob_units(prev), b);
470	}
471out:
472	spin_unlock_irqrestore(&slob_lock, flags);
473}
474
475/*
476 * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
477 */
478
479void *__kmalloc_node(size_t size, gfp_t gfp, int node)
 
480{
481	unsigned int *m;
482	int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
483	void *ret;
484
485	gfp &= gfp_allowed_mask;
486
487	lockdep_trace_alloc(gfp);
488
489	if (size < PAGE_SIZE - align) {
490		if (!size)
491			return ZERO_SIZE_PTR;
492
493		m = slob_alloc(size + align, gfp, align, node);
494
495		if (!m)
496			return NULL;
497		*m = size;
498		ret = (void *)m + align;
499
500		trace_kmalloc_node(_RET_IP_, ret,
501				   size, size + align, gfp, node);
502	} else {
503		unsigned int order = get_order(size);
504
505		if (likely(order))
506			gfp |= __GFP_COMP;
507		ret = slob_new_pages(gfp, order, node);
508		if (ret) {
509			struct page *page;
510			page = virt_to_page(ret);
511			page->private = size;
512		}
513
514		trace_kmalloc_node(_RET_IP_, ret,
515				   size, PAGE_SIZE << order, gfp, node);
516	}
517
518	kmemleak_alloc(ret, size, 1, gfp);
519	return ret;
520}
521EXPORT_SYMBOL(__kmalloc_node);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
522
523void kfree(const void *block)
524{
525	struct slob_page *sp;
526
527	trace_kfree(_RET_IP_, block);
528
529	if (unlikely(ZERO_OR_NULL_PTR(block)))
530		return;
531	kmemleak_free(block);
532
533	sp = slob_page(block);
534	if (is_slob_page(sp)) {
535		int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
536		unsigned int *m = (unsigned int *)(block - align);
537		slob_free(m, *m + align);
538	} else
539		put_page(&sp->page);
540}
541EXPORT_SYMBOL(kfree);
542
543/* can't use ksize for kmem_cache_alloc memory, only kmalloc */
544size_t ksize(const void *block)
545{
546	struct slob_page *sp;
 
 
547
548	BUG_ON(!block);
549	if (unlikely(block == ZERO_SIZE_PTR))
550		return 0;
551
552	sp = slob_page(block);
553	if (is_slob_page(sp)) {
554		int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
555		unsigned int *m = (unsigned int *)(block - align);
556		return SLOB_UNITS(*m) * SLOB_UNIT;
557	} else
558		return sp->page.private;
559}
560EXPORT_SYMBOL(ksize);
561
562struct kmem_cache {
563	unsigned int size, align;
564	unsigned long flags;
565	const char *name;
566	void (*ctor)(void *);
567};
568
569struct kmem_cache *kmem_cache_create(const char *name, size_t size,
570	size_t align, unsigned long flags, void (*ctor)(void *))
571{
572	struct kmem_cache *c;
573
574	c = slob_alloc(sizeof(struct kmem_cache),
575		GFP_KERNEL, ARCH_KMALLOC_MINALIGN, -1);
576
577	if (c) {
578		c->name = name;
579		c->size = size;
580		if (flags & SLAB_DESTROY_BY_RCU) {
581			/* leave room for rcu footer at the end of object */
582			c->size += sizeof(struct slob_rcu);
583		}
584		c->flags = flags;
585		c->ctor = ctor;
586		/* ignore alignment unless it's forced */
587		c->align = (flags & SLAB_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
588		if (c->align < ARCH_SLAB_MINALIGN)
589			c->align = ARCH_SLAB_MINALIGN;
590		if (c->align < align)
591			c->align = align;
592	} else if (flags & SLAB_PANIC)
593		panic("Cannot create slab cache %s\n", name);
594
595	kmemleak_alloc(c, sizeof(struct kmem_cache), 1, GFP_KERNEL);
596	return c;
597}
598EXPORT_SYMBOL(kmem_cache_create);
599
600void kmem_cache_destroy(struct kmem_cache *c)
601{
602	kmemleak_free(c);
603	if (c->flags & SLAB_DESTROY_BY_RCU)
604		rcu_barrier();
605	slob_free(c, sizeof(struct kmem_cache));
606}
607EXPORT_SYMBOL(kmem_cache_destroy);
608
609void *kmem_cache_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
610{
611	void *b;
612
613	flags &= gfp_allowed_mask;
614
615	lockdep_trace_alloc(flags);
616
617	if (c->size < PAGE_SIZE) {
618		b = slob_alloc(c->size, flags, c->align, node);
619		trace_kmem_cache_alloc_node(_RET_IP_, b, c->size,
620					    SLOB_UNITS(c->size) * SLOB_UNIT,
621					    flags, node);
622	} else {
623		b = slob_new_pages(flags, get_order(c->size), node);
624		trace_kmem_cache_alloc_node(_RET_IP_, b, c->size,
625					    PAGE_SIZE << get_order(c->size),
626					    flags, node);
627	}
628
629	if (c->ctor)
630		c->ctor(b);
631
632	kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
633	return b;
634}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
635EXPORT_SYMBOL(kmem_cache_alloc_node);
 
636
637static void __kmem_cache_free(void *b, int size)
638{
639	if (size < PAGE_SIZE)
640		slob_free(b, size);
641	else
642		slob_free_pages(b, get_order(size));
643}
644
645static void kmem_rcu_free(struct rcu_head *head)
646{
647	struct slob_rcu *slob_rcu = (struct slob_rcu *)head;
648	void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));
649
650	__kmem_cache_free(b, slob_rcu->size);
651}
652
653void kmem_cache_free(struct kmem_cache *c, void *b)
654{
655	kmemleak_free_recursive(b, c->flags);
656	if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) {
657		struct slob_rcu *slob_rcu;
658		slob_rcu = b + (c->size - sizeof(struct slob_rcu));
659		slob_rcu->size = c->size;
660		call_rcu(&slob_rcu->head, kmem_rcu_free);
661	} else {
662		__kmem_cache_free(b, c->size);
663	}
664
665	trace_kmem_cache_free(_RET_IP_, b);
666}
667EXPORT_SYMBOL(kmem_cache_free);
668
669unsigned int kmem_cache_size(struct kmem_cache *c)
670{
671	return c->size;
672}
673EXPORT_SYMBOL(kmem_cache_size);
674
675int kmem_cache_shrink(struct kmem_cache *d)
 
676{
 
 
 
 
 
 
 
677	return 0;
678}
679EXPORT_SYMBOL(kmem_cache_shrink);
680
681static unsigned int slob_ready __read_mostly;
 
 
682
683int slab_is_available(void)
684{
685	return slob_ready;
686}
687
 
 
 
 
 
 
 
688void __init kmem_cache_init(void)
689{
690	slob_ready = 1;
 
691}
692
693void __init kmem_cache_init_late(void)
694{
695	/* Nothing to do */
696}
v4.6
  1/*
  2 * SLOB Allocator: Simple List Of Blocks
  3 *
  4 * Matt Mackall <mpm@selenic.com> 12/30/03
  5 *
  6 * NUMA support by Paul Mundt, 2007.
  7 *
  8 * How SLOB works:
  9 *
 10 * The core of SLOB is a traditional K&R style heap allocator, with
 11 * support for returning aligned objects. The granularity of this
 12 * allocator is as little as 2 bytes, however typically most architectures
 13 * will require 4 bytes on 32-bit and 8 bytes on 64-bit.
 14 *
 15 * The slob heap is a set of linked list of pages from alloc_pages(),
 16 * and within each page, there is a singly-linked list of free blocks
 17 * (slob_t). The heap is grown on demand. To reduce fragmentation,
 18 * heap pages are segregated into three lists, with objects less than
 19 * 256 bytes, objects less than 1024 bytes, and all other objects.
 20 *
 21 * Allocation from heap involves first searching for a page with
 22 * sufficient free blocks (using a next-fit-like approach) followed by
 23 * a first-fit scan of the page. Deallocation inserts objects back
 24 * into the free list in address order, so this is effectively an
 25 * address-ordered first fit.
 26 *
 27 * Above this is an implementation of kmalloc/kfree. Blocks returned
 28 * from kmalloc are prepended with a 4-byte header with the kmalloc size.
 29 * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
 30 * alloc_pages() directly, allocating compound pages so the page order
 31 * does not have to be separately tracked.
 32 * These objects are detected in kfree() because PageSlab()
 
 33 * is false for them.
 34 *
 35 * SLAB is emulated on top of SLOB by simply calling constructors and
 36 * destructors for every SLAB allocation. Objects are returned with the
 37 * 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which
 38 * case the low-level allocator will fragment blocks to create the proper
 39 * alignment. Again, objects of page-size or greater are allocated by
 40 * calling alloc_pages(). As SLAB objects know their size, no separate
 41 * size bookkeeping is necessary and there is essentially no allocation
 42 * space overhead, and compound pages aren't needed for multi-page
 43 * allocations.
 44 *
 45 * NUMA support in SLOB is fairly simplistic, pushing most of the real
 46 * logic down to the page allocator, and simply doing the node accounting
 47 * on the upper levels. In the event that a node id is explicitly
 48 * provided, __alloc_pages_node() with the specified node id is used
 49 * instead. The common case (or when the node id isn't explicitly provided)
 50 * will default to the current node, as per numa_node_id().
 51 *
 52 * Node aware pages are still inserted in to the global freelist, and
 53 * these are scanned for by matching against the node id encoded in the
 54 * page flags. As a result, block allocations that can be satisfied from
 55 * the freelist will only be done so on pages residing on the same node,
 56 * in order to prevent random node placement.
 57 */
 58
 59#include <linux/kernel.h>
 60#include <linux/slab.h>
 61
 62#include <linux/mm.h>
 63#include <linux/swap.h> /* struct reclaim_state */
 64#include <linux/cache.h>
 65#include <linux/init.h>
 66#include <linux/export.h>
 67#include <linux/rcupdate.h>
 68#include <linux/list.h>
 69#include <linux/kmemleak.h>
 70
 71#include <trace/events/kmem.h>
 72
 73#include <linux/atomic.h>
 74
 75#include "slab.h"
 76/*
 77 * slob_block has a field 'units', which indicates size of block if +ve,
 78 * or offset of next block if -ve (in SLOB_UNITs).
 79 *
 80 * Free blocks of size 1 unit simply contain the offset of the next block.
 81 * Those with larger size contain their size in the first SLOB_UNIT of
 82 * memory, and the offset of the next free block in the second SLOB_UNIT.
 83 */
 84#if PAGE_SIZE <= (32767 * 2)
 85typedef s16 slobidx_t;
 86#else
 87typedef s32 slobidx_t;
 88#endif
 89
 90struct slob_block {
 91	slobidx_t units;
 92};
 93typedef struct slob_block slob_t;
 94
 95/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 96 * All partially free slob pages go on these lists.
 97 */
 98#define SLOB_BREAK1 256
 99#define SLOB_BREAK2 1024
100static LIST_HEAD(free_slob_small);
101static LIST_HEAD(free_slob_medium);
102static LIST_HEAD(free_slob_large);
103
104/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
105 * slob_page_free: true for pages on free_slob_pages list.
106 */
107static inline int slob_page_free(struct page *sp)
108{
109	return PageSlobFree(sp);
110}
111
112static void set_slob_page_free(struct page *sp, struct list_head *list)
113{
114	list_add(&sp->lru, list);
115	__SetPageSlobFree(sp);
116}
117
118static inline void clear_slob_page_free(struct page *sp)
119{
120	list_del(&sp->lru);
121	__ClearPageSlobFree(sp);
122}
123
124#define SLOB_UNIT sizeof(slob_t)
125#define SLOB_UNITS(size) DIV_ROUND_UP(size, SLOB_UNIT)
 
126
127/*
128 * struct slob_rcu is inserted at the tail of allocated slob blocks, which
129 * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
130 * the block using call_rcu.
131 */
132struct slob_rcu {
133	struct rcu_head head;
134	int size;
135};
136
137/*
138 * slob_lock protects all slob allocator structures.
139 */
140static DEFINE_SPINLOCK(slob_lock);
141
142/*
143 * Encode the given size and next info into a free slob block s.
144 */
145static void set_slob(slob_t *s, slobidx_t size, slob_t *next)
146{
147	slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
148	slobidx_t offset = next - base;
149
150	if (size > 1) {
151		s[0].units = size;
152		s[1].units = offset;
153	} else
154		s[0].units = -offset;
155}
156
157/*
158 * Return the size of a slob block.
159 */
160static slobidx_t slob_units(slob_t *s)
161{
162	if (s->units > 0)
163		return s->units;
164	return 1;
165}
166
167/*
168 * Return the next free slob block pointer after this one.
169 */
170static slob_t *slob_next(slob_t *s)
171{
172	slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
173	slobidx_t next;
174
175	if (s[0].units < 0)
176		next = -s[0].units;
177	else
178		next = s[1].units;
179	return base+next;
180}
181
182/*
183 * Returns true if s is the last free block in its page.
184 */
185static int slob_last(slob_t *s)
186{
187	return !((unsigned long)slob_next(s) & ~PAGE_MASK);
188}
189
190static void *slob_new_pages(gfp_t gfp, int order, int node)
191{
192	void *page;
193
194#ifdef CONFIG_NUMA
195	if (node != NUMA_NO_NODE)
196		page = __alloc_pages_node(node, gfp, order);
197	else
198#endif
199		page = alloc_pages(gfp, order);
200
201	if (!page)
202		return NULL;
203
204	return page_address(page);
205}
206
207static void slob_free_pages(void *b, int order)
208{
209	if (current->reclaim_state)
210		current->reclaim_state->reclaimed_slab += 1 << order;
211	free_pages((unsigned long)b, order);
212}
213
214/*
215 * Allocate a slob block within a given slob_page sp.
216 */
217static void *slob_page_alloc(struct page *sp, size_t size, int align)
218{
219	slob_t *prev, *cur, *aligned = NULL;
220	int delta = 0, units = SLOB_UNITS(size);
221
222	for (prev = NULL, cur = sp->freelist; ; prev = cur, cur = slob_next(cur)) {
223		slobidx_t avail = slob_units(cur);
224
225		if (align) {
226			aligned = (slob_t *)ALIGN((unsigned long)cur, align);
227			delta = aligned - cur;
228		}
229		if (avail >= units + delta) { /* room enough? */
230			slob_t *next;
231
232			if (delta) { /* need to fragment head to align? */
233				next = slob_next(cur);
234				set_slob(aligned, avail - delta, next);
235				set_slob(cur, delta, aligned);
236				prev = cur;
237				cur = aligned;
238				avail = slob_units(cur);
239			}
240
241			next = slob_next(cur);
242			if (avail == units) { /* exact fit? unlink. */
243				if (prev)
244					set_slob(prev, slob_units(prev), next);
245				else
246					sp->freelist = next;
247			} else { /* fragment */
248				if (prev)
249					set_slob(prev, slob_units(prev), cur + units);
250				else
251					sp->freelist = cur + units;
252				set_slob(cur + units, avail - units, next);
253			}
254
255			sp->units -= units;
256			if (!sp->units)
257				clear_slob_page_free(sp);
258			return cur;
259		}
260		if (slob_last(cur))
261			return NULL;
262	}
263}
264
265/*
266 * slob_alloc: entry point into the slob allocator.
267 */
268static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
269{
270	struct page *sp;
271	struct list_head *prev;
272	struct list_head *slob_list;
273	slob_t *b = NULL;
274	unsigned long flags;
275
276	if (size < SLOB_BREAK1)
277		slob_list = &free_slob_small;
278	else if (size < SLOB_BREAK2)
279		slob_list = &free_slob_medium;
280	else
281		slob_list = &free_slob_large;
282
283	spin_lock_irqsave(&slob_lock, flags);
284	/* Iterate through each partially free page, try to find room */
285	list_for_each_entry(sp, slob_list, lru) {
286#ifdef CONFIG_NUMA
287		/*
288		 * If there's a node specification, search for a partial
289		 * page with a matching node id in the freelist.
290		 */
291		if (node != NUMA_NO_NODE && page_to_nid(sp) != node)
292			continue;
293#endif
294		/* Enough room on this page? */
295		if (sp->units < SLOB_UNITS(size))
296			continue;
297
298		/* Attempt to alloc */
299		prev = sp->lru.prev;
300		b = slob_page_alloc(sp, size, align);
301		if (!b)
302			continue;
303
304		/* Improve fragment distribution and reduce our average
305		 * search time by starting our next search here. (see
306		 * Knuth vol 1, sec 2.5, pg 449) */
307		if (prev != slob_list->prev &&
308				slob_list->next != prev->next)
309			list_move_tail(slob_list, prev->next);
310		break;
311	}
312	spin_unlock_irqrestore(&slob_lock, flags);
313
314	/* Not enough space: must allocate a new page */
315	if (!b) {
316		b = slob_new_pages(gfp & ~__GFP_ZERO, 0, node);
317		if (!b)
318			return NULL;
319		sp = virt_to_page(b);
320		__SetPageSlab(sp);
321
322		spin_lock_irqsave(&slob_lock, flags);
323		sp->units = SLOB_UNITS(PAGE_SIZE);
324		sp->freelist = b;
325		INIT_LIST_HEAD(&sp->lru);
326		set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
327		set_slob_page_free(sp, slob_list);
328		b = slob_page_alloc(sp, size, align);
329		BUG_ON(!b);
330		spin_unlock_irqrestore(&slob_lock, flags);
331	}
332	if (unlikely((gfp & __GFP_ZERO) && b))
333		memset(b, 0, size);
334	return b;
335}
336
337/*
338 * slob_free: entry point into the slob allocator.
339 */
340static void slob_free(void *block, int size)
341{
342	struct page *sp;
343	slob_t *prev, *next, *b = (slob_t *)block;
344	slobidx_t units;
345	unsigned long flags;
346	struct list_head *slob_list;
347
348	if (unlikely(ZERO_OR_NULL_PTR(block)))
349		return;
350	BUG_ON(!size);
351
352	sp = virt_to_page(block);
353	units = SLOB_UNITS(size);
354
355	spin_lock_irqsave(&slob_lock, flags);
356
357	if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {
358		/* Go directly to page allocator. Do not pass slob allocator */
359		if (slob_page_free(sp))
360			clear_slob_page_free(sp);
361		spin_unlock_irqrestore(&slob_lock, flags);
362		__ClearPageSlab(sp);
363		page_mapcount_reset(sp);
364		slob_free_pages(b, 0);
365		return;
366	}
367
368	if (!slob_page_free(sp)) {
369		/* This slob page is about to become partially free. Easy! */
370		sp->units = units;
371		sp->freelist = b;
372		set_slob(b, units,
373			(void *)((unsigned long)(b +
374					SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
375		if (size < SLOB_BREAK1)
376			slob_list = &free_slob_small;
377		else if (size < SLOB_BREAK2)
378			slob_list = &free_slob_medium;
379		else
380			slob_list = &free_slob_large;
381		set_slob_page_free(sp, slob_list);
382		goto out;
383	}
384
385	/*
386	 * Otherwise the page is already partially free, so find reinsertion
387	 * point.
388	 */
389	sp->units += units;
390
391	if (b < (slob_t *)sp->freelist) {
392		if (b + units == sp->freelist) {
393			units += slob_units(sp->freelist);
394			sp->freelist = slob_next(sp->freelist);
395		}
396		set_slob(b, units, sp->freelist);
397		sp->freelist = b;
398	} else {
399		prev = sp->freelist;
400		next = slob_next(prev);
401		while (b > next) {
402			prev = next;
403			next = slob_next(prev);
404		}
405
406		if (!slob_last(prev) && b + units == next) {
407			units += slob_units(next);
408			set_slob(b, units, slob_next(next));
409		} else
410			set_slob(b, units, next);
411
412		if (prev + slob_units(prev) == b) {
413			units = slob_units(b) + slob_units(prev);
414			set_slob(prev, units, slob_next(b));
415		} else
416			set_slob(prev, slob_units(prev), b);
417	}
418out:
419	spin_unlock_irqrestore(&slob_lock, flags);
420}
421
422/*
423 * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
424 */
425
426static __always_inline void *
427__do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller)
428{
429	unsigned int *m;
430	int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
431	void *ret;
432
433	gfp &= gfp_allowed_mask;
434
435	lockdep_trace_alloc(gfp);
436
437	if (size < PAGE_SIZE - align) {
438		if (!size)
439			return ZERO_SIZE_PTR;
440
441		m = slob_alloc(size + align, gfp, align, node);
442
443		if (!m)
444			return NULL;
445		*m = size;
446		ret = (void *)m + align;
447
448		trace_kmalloc_node(caller, ret,
449				   size, size + align, gfp, node);
450	} else {
451		unsigned int order = get_order(size);
452
453		if (likely(order))
454			gfp |= __GFP_COMP;
455		ret = slob_new_pages(gfp, order, node);
 
 
 
 
 
456
457		trace_kmalloc_node(caller, ret,
458				   size, PAGE_SIZE << order, gfp, node);
459	}
460
461	kmemleak_alloc(ret, size, 1, gfp);
462	return ret;
463}
464
465void *__kmalloc(size_t size, gfp_t gfp)
466{
467	return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, _RET_IP_);
468}
469EXPORT_SYMBOL(__kmalloc);
470
471void *__kmalloc_track_caller(size_t size, gfp_t gfp, unsigned long caller)
472{
473	return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, caller);
474}
475
476#ifdef CONFIG_NUMA
477void *__kmalloc_node_track_caller(size_t size, gfp_t gfp,
478					int node, unsigned long caller)
479{
480	return __do_kmalloc_node(size, gfp, node, caller);
481}
482#endif
483
484void kfree(const void *block)
485{
486	struct page *sp;
487
488	trace_kfree(_RET_IP_, block);
489
490	if (unlikely(ZERO_OR_NULL_PTR(block)))
491		return;
492	kmemleak_free(block);
493
494	sp = virt_to_page(block);
495	if (PageSlab(sp)) {
496		int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
497		unsigned int *m = (unsigned int *)(block - align);
498		slob_free(m, *m + align);
499	} else
500		__free_pages(sp, compound_order(sp));
501}
502EXPORT_SYMBOL(kfree);
503
504/* can't use ksize for kmem_cache_alloc memory, only kmalloc */
505size_t ksize(const void *block)
506{
507	struct page *sp;
508	int align;
509	unsigned int *m;
510
511	BUG_ON(!block);
512	if (unlikely(block == ZERO_SIZE_PTR))
513		return 0;
514
515	sp = virt_to_page(block);
516	if (unlikely(!PageSlab(sp)))
517		return PAGE_SIZE << compound_order(sp);
518
519	align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
520	m = (unsigned int *)(block - align);
521	return SLOB_UNITS(*m) * SLOB_UNIT;
522}
523EXPORT_SYMBOL(ksize);
524
525int __kmem_cache_create(struct kmem_cache *c, unsigned long flags)
 
 
 
 
 
 
 
 
526{
527	if (flags & SLAB_DESTROY_BY_RCU) {
528		/* leave room for rcu footer at the end of object */
529		c->size += sizeof(struct slob_rcu);
530	}
531	c->flags = flags;
532	return 0;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
533}
 
534
535static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
536{
537	void *b;
538
539	flags &= gfp_allowed_mask;
540
541	lockdep_trace_alloc(flags);
542
543	if (c->size < PAGE_SIZE) {
544		b = slob_alloc(c->size, flags, c->align, node);
545		trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size,
546					    SLOB_UNITS(c->size) * SLOB_UNIT,
547					    flags, node);
548	} else {
549		b = slob_new_pages(flags, get_order(c->size), node);
550		trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size,
551					    PAGE_SIZE << get_order(c->size),
552					    flags, node);
553	}
554
555	if (b && c->ctor)
556		c->ctor(b);
557
558	kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
559	return b;
560}
561
562void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
563{
564	return slob_alloc_node(cachep, flags, NUMA_NO_NODE);
565}
566EXPORT_SYMBOL(kmem_cache_alloc);
567
568#ifdef CONFIG_NUMA
569void *__kmalloc_node(size_t size, gfp_t gfp, int node)
570{
571	return __do_kmalloc_node(size, gfp, node, _RET_IP_);
572}
573EXPORT_SYMBOL(__kmalloc_node);
574
575void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t gfp, int node)
576{
577	return slob_alloc_node(cachep, gfp, node);
578}
579EXPORT_SYMBOL(kmem_cache_alloc_node);
580#endif
581
582static void __kmem_cache_free(void *b, int size)
583{
584	if (size < PAGE_SIZE)
585		slob_free(b, size);
586	else
587		slob_free_pages(b, get_order(size));
588}
589
590static void kmem_rcu_free(struct rcu_head *head)
591{
592	struct slob_rcu *slob_rcu = (struct slob_rcu *)head;
593	void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));
594
595	__kmem_cache_free(b, slob_rcu->size);
596}
597
598void kmem_cache_free(struct kmem_cache *c, void *b)
599{
600	kmemleak_free_recursive(b, c->flags);
601	if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) {
602		struct slob_rcu *slob_rcu;
603		slob_rcu = b + (c->size - sizeof(struct slob_rcu));
604		slob_rcu->size = c->size;
605		call_rcu(&slob_rcu->head, kmem_rcu_free);
606	} else {
607		__kmem_cache_free(b, c->size);
608	}
609
610	trace_kmem_cache_free(_RET_IP_, b);
611}
612EXPORT_SYMBOL(kmem_cache_free);
613
614void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
615{
616	__kmem_cache_free_bulk(s, size, p);
617}
618EXPORT_SYMBOL(kmem_cache_free_bulk);
619
620int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
621								void **p)
622{
623	return __kmem_cache_alloc_bulk(s, flags, size, p);
624}
625EXPORT_SYMBOL(kmem_cache_alloc_bulk);
626
627int __kmem_cache_shutdown(struct kmem_cache *c)
628{
629	/* No way to check for remaining objects */
630	return 0;
631}
 
632
633void __kmem_cache_release(struct kmem_cache *c)
634{
635}
636
637int __kmem_cache_shrink(struct kmem_cache *d, bool deactivate)
638{
639	return 0;
640}
641
642struct kmem_cache kmem_cache_boot = {
643	.name = "kmem_cache",
644	.size = sizeof(struct kmem_cache),
645	.flags = SLAB_PANIC,
646	.align = ARCH_KMALLOC_MINALIGN,
647};
648
649void __init kmem_cache_init(void)
650{
651	kmem_cache = &kmem_cache_boot;
652	slab_state = UP;
653}
654
655void __init kmem_cache_init_late(void)
656{
657	slab_state = FULL;
658}