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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}
v5.9
  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * SLOB Allocator: Simple List Of Blocks
  4 *
  5 * Matt Mackall <mpm@selenic.com> 12/30/03
  6 *
  7 * NUMA support by Paul Mundt, 2007.
  8 *
  9 * How SLOB works:
 10 *
 11 * The core of SLOB is a traditional K&R style heap allocator, with
 12 * support for returning aligned objects. The granularity of this
 13 * allocator is as little as 2 bytes, however typically most architectures
 14 * will require 4 bytes on 32-bit and 8 bytes on 64-bit.
 15 *
 16 * The slob heap is a set of linked list of pages from alloc_pages(),
 17 * and within each page, there is a singly-linked list of free blocks
 18 * (slob_t). The heap is grown on demand. To reduce fragmentation,
 19 * heap pages are segregated into three lists, with objects less than
 20 * 256 bytes, objects less than 1024 bytes, and all other objects.
 21 *
 22 * Allocation from heap involves first searching for a page with
 23 * sufficient free blocks (using a next-fit-like approach) followed by
 24 * a first-fit scan of the page. Deallocation inserts objects back
 25 * into the free list in address order, so this is effectively an
 26 * address-ordered first fit.
 27 *
 28 * Above this is an implementation of kmalloc/kfree. Blocks returned
 29 * from kmalloc are prepended with a 4-byte header with the kmalloc size.
 30 * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
 31 * alloc_pages() directly, allocating compound pages so the page order
 32 * does not have to be separately tracked.
 33 * These objects are detected in kfree() because PageSlab()
 
 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_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
 63#include <linux/mm.h>
 64#include <linux/swap.h> /* struct reclaim_state */
 65#include <linux/cache.h>
 66#include <linux/init.h>
 67#include <linux/export.h>
 68#include <linux/rcupdate.h>
 69#include <linux/list.h>
 70#include <linux/kmemleak.h>
 71
 72#include <trace/events/kmem.h>
 73
 74#include <linux/atomic.h>
 75
 76#include "slab.h"
 77/*
 78 * slob_block has a field 'units', which indicates size of block if +ve,
 79 * or offset of next block if -ve (in SLOB_UNITs).
 80 *
 81 * Free blocks of size 1 unit simply contain the offset of the next block.
 82 * Those with larger size contain their size in the first SLOB_UNIT of
 83 * memory, and the offset of the next free block in the second SLOB_UNIT.
 84 */
 85#if PAGE_SIZE <= (32767 * 2)
 86typedef s16 slobidx_t;
 87#else
 88typedef s32 slobidx_t;
 89#endif
 90
 91struct slob_block {
 92	slobidx_t units;
 93};
 94typedef struct slob_block slob_t;
 95
 96/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 97 * All partially free slob pages go on these lists.
 98 */
 99#define SLOB_BREAK1 256
100#define SLOB_BREAK2 1024
101static LIST_HEAD(free_slob_small);
102static LIST_HEAD(free_slob_medium);
103static LIST_HEAD(free_slob_large);
104
105/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
106 * slob_page_free: true for pages on free_slob_pages list.
107 */
108static inline int slob_page_free(struct page *sp)
109{
110	return PageSlobFree(sp);
111}
112
113static void set_slob_page_free(struct page *sp, struct list_head *list)
114{
115	list_add(&sp->slab_list, list);
116	__SetPageSlobFree(sp);
117}
118
119static inline void clear_slob_page_free(struct page *sp)
120{
121	list_del(&sp->slab_list);
122	__ClearPageSlobFree(sp);
123}
124
125#define SLOB_UNIT sizeof(slob_t)
126#define SLOB_UNITS(size) DIV_ROUND_UP(size, SLOB_UNIT)
 
127
128/*
129 * struct slob_rcu is inserted at the tail of allocated slob blocks, which
130 * were created with a SLAB_TYPESAFE_BY_RCU slab. slob_rcu is used to free
131 * the block using call_rcu.
132 */
133struct slob_rcu {
134	struct rcu_head head;
135	int size;
136};
137
138/*
139 * slob_lock protects all slob allocator structures.
140 */
141static DEFINE_SPINLOCK(slob_lock);
142
143/*
144 * Encode the given size and next info into a free slob block s.
145 */
146static void set_slob(slob_t *s, slobidx_t size, slob_t *next)
147{
148	slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
149	slobidx_t offset = next - base;
150
151	if (size > 1) {
152		s[0].units = size;
153		s[1].units = offset;
154	} else
155		s[0].units = -offset;
156}
157
158/*
159 * Return the size of a slob block.
160 */
161static slobidx_t slob_units(slob_t *s)
162{
163	if (s->units > 0)
164		return s->units;
165	return 1;
166}
167
168/*
169 * Return the next free slob block pointer after this one.
170 */
171static slob_t *slob_next(slob_t *s)
172{
173	slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
174	slobidx_t next;
175
176	if (s[0].units < 0)
177		next = -s[0].units;
178	else
179		next = s[1].units;
180	return base+next;
181}
182
183/*
184 * Returns true if s is the last free block in its page.
185 */
186static int slob_last(slob_t *s)
187{
188	return !((unsigned long)slob_next(s) & ~PAGE_MASK);
189}
190
191static void *slob_new_pages(gfp_t gfp, int order, int node)
192{
193	struct page *page;
194
195#ifdef CONFIG_NUMA
196	if (node != NUMA_NO_NODE)
197		page = __alloc_pages_node(node, gfp, order);
198	else
199#endif
200		page = alloc_pages(gfp, order);
201
202	if (!page)
203		return NULL;
204
205	mod_node_page_state(page_pgdat(page), NR_SLAB_UNRECLAIMABLE_B,
206			    PAGE_SIZE << order);
207	return page_address(page);
208}
209
210static void slob_free_pages(void *b, int order)
211{
212	struct page *sp = virt_to_page(b);
213
214	if (current->reclaim_state)
215		current->reclaim_state->reclaimed_slab += 1 << order;
216
217	mod_node_page_state(page_pgdat(sp), NR_SLAB_UNRECLAIMABLE_B,
218			    -(PAGE_SIZE << order));
219	__free_pages(sp, order);
220}
221
222/*
223 * slob_page_alloc() - Allocate a slob block within a given slob_page sp.
224 * @sp: Page to look in.
225 * @size: Size of the allocation.
226 * @align: Allocation alignment.
227 * @align_offset: Offset in the allocated block that will be aligned.
228 * @page_removed_from_list: Return parameter.
229 *
230 * Tries to find a chunk of memory at least @size bytes big within @page.
231 *
232 * Return: Pointer to memory if allocated, %NULL otherwise.  If the
233 *         allocation fills up @page then the page is removed from the
234 *         freelist, in this case @page_removed_from_list will be set to
235 *         true (set to false otherwise).
236 */
237static void *slob_page_alloc(struct page *sp, size_t size, int align,
238			      int align_offset, bool *page_removed_from_list)
239{
240	slob_t *prev, *cur, *aligned = NULL;
241	int delta = 0, units = SLOB_UNITS(size);
242
243	*page_removed_from_list = false;
244	for (prev = NULL, cur = sp->freelist; ; prev = cur, cur = slob_next(cur)) {
245		slobidx_t avail = slob_units(cur);
246
247		/*
248		 * 'aligned' will hold the address of the slob block so that the
249		 * address 'aligned'+'align_offset' is aligned according to the
250		 * 'align' parameter. This is for kmalloc() which prepends the
251		 * allocated block with its size, so that the block itself is
252		 * aligned when needed.
253		 */
254		if (align) {
255			aligned = (slob_t *)
256				(ALIGN((unsigned long)cur + align_offset, align)
257				 - align_offset);
258			delta = aligned - cur;
259		}
260		if (avail >= units + delta) { /* room enough? */
261			slob_t *next;
262
263			if (delta) { /* need to fragment head to align? */
264				next = slob_next(cur);
265				set_slob(aligned, avail - delta, next);
266				set_slob(cur, delta, aligned);
267				prev = cur;
268				cur = aligned;
269				avail = slob_units(cur);
270			}
271
272			next = slob_next(cur);
273			if (avail == units) { /* exact fit? unlink. */
274				if (prev)
275					set_slob(prev, slob_units(prev), next);
276				else
277					sp->freelist = next;
278			} else { /* fragment */
279				if (prev)
280					set_slob(prev, slob_units(prev), cur + units);
281				else
282					sp->freelist = cur + units;
283				set_slob(cur + units, avail - units, next);
284			}
285
286			sp->units -= units;
287			if (!sp->units) {
288				clear_slob_page_free(sp);
289				*page_removed_from_list = true;
290			}
291			return cur;
292		}
293		if (slob_last(cur))
294			return NULL;
295	}
296}
297
298/*
299 * slob_alloc: entry point into the slob allocator.
300 */
301static void *slob_alloc(size_t size, gfp_t gfp, int align, int node,
302							int align_offset)
303{
304	struct page *sp;
 
305	struct list_head *slob_list;
306	slob_t *b = NULL;
307	unsigned long flags;
308	bool _unused;
309
310	if (size < SLOB_BREAK1)
311		slob_list = &free_slob_small;
312	else if (size < SLOB_BREAK2)
313		slob_list = &free_slob_medium;
314	else
315		slob_list = &free_slob_large;
316
317	spin_lock_irqsave(&slob_lock, flags);
318	/* Iterate through each partially free page, try to find room */
319	list_for_each_entry(sp, slob_list, slab_list) {
320		bool page_removed_from_list = false;
321#ifdef CONFIG_NUMA
322		/*
323		 * If there's a node specification, search for a partial
324		 * page with a matching node id in the freelist.
325		 */
326		if (node != NUMA_NO_NODE && page_to_nid(sp) != node)
327			continue;
328#endif
329		/* Enough room on this page? */
330		if (sp->units < SLOB_UNITS(size))
331			continue;
332
333		b = slob_page_alloc(sp, size, align, align_offset, &page_removed_from_list);
 
 
334		if (!b)
335			continue;
336
337		/*
338		 * If slob_page_alloc() removed sp from the list then we
339		 * cannot call list functions on sp.  If so allocation
340		 * did not fragment the page anyway so optimisation is
341		 * unnecessary.
342		 */
343		if (!page_removed_from_list) {
344			/*
345			 * Improve fragment distribution and reduce our average
346			 * search time by starting our next search here. (see
347			 * Knuth vol 1, sec 2.5, pg 449)
348			 */
349			if (!list_is_first(&sp->slab_list, slob_list))
350				list_rotate_to_front(&sp->slab_list, slob_list);
351		}
352		break;
353	}
354	spin_unlock_irqrestore(&slob_lock, flags);
355
356	/* Not enough space: must allocate a new page */
357	if (!b) {
358		b = slob_new_pages(gfp & ~__GFP_ZERO, 0, node);
359		if (!b)
360			return NULL;
361		sp = virt_to_page(b);
362		__SetPageSlab(sp);
363
364		spin_lock_irqsave(&slob_lock, flags);
365		sp->units = SLOB_UNITS(PAGE_SIZE);
366		sp->freelist = b;
367		INIT_LIST_HEAD(&sp->slab_list);
368		set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
369		set_slob_page_free(sp, slob_list);
370		b = slob_page_alloc(sp, size, align, align_offset, &_unused);
371		BUG_ON(!b);
372		spin_unlock_irqrestore(&slob_lock, flags);
373	}
374	if (unlikely(gfp & __GFP_ZERO))
375		memset(b, 0, size);
376	return b;
377}
378
379/*
380 * slob_free: entry point into the slob allocator.
381 */
382static void slob_free(void *block, int size)
383{
384	struct page *sp;
385	slob_t *prev, *next, *b = (slob_t *)block;
386	slobidx_t units;
387	unsigned long flags;
388	struct list_head *slob_list;
389
390	if (unlikely(ZERO_OR_NULL_PTR(block)))
391		return;
392	BUG_ON(!size);
393
394	sp = virt_to_page(block);
395	units = SLOB_UNITS(size);
396
397	spin_lock_irqsave(&slob_lock, flags);
398
399	if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {
400		/* Go directly to page allocator. Do not pass slob allocator */
401		if (slob_page_free(sp))
402			clear_slob_page_free(sp);
403		spin_unlock_irqrestore(&slob_lock, flags);
404		__ClearPageSlab(sp);
405		page_mapcount_reset(sp);
406		slob_free_pages(b, 0);
407		return;
408	}
409
410	if (!slob_page_free(sp)) {
411		/* This slob page is about to become partially free. Easy! */
412		sp->units = units;
413		sp->freelist = b;
414		set_slob(b, units,
415			(void *)((unsigned long)(b +
416					SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
417		if (size < SLOB_BREAK1)
418			slob_list = &free_slob_small;
419		else if (size < SLOB_BREAK2)
420			slob_list = &free_slob_medium;
421		else
422			slob_list = &free_slob_large;
423		set_slob_page_free(sp, slob_list);
424		goto out;
425	}
426
427	/*
428	 * Otherwise the page is already partially free, so find reinsertion
429	 * point.
430	 */
431	sp->units += units;
432
433	if (b < (slob_t *)sp->freelist) {
434		if (b + units == sp->freelist) {
435			units += slob_units(sp->freelist);
436			sp->freelist = slob_next(sp->freelist);
437		}
438		set_slob(b, units, sp->freelist);
439		sp->freelist = b;
440	} else {
441		prev = sp->freelist;
442		next = slob_next(prev);
443		while (b > next) {
444			prev = next;
445			next = slob_next(prev);
446		}
447
448		if (!slob_last(prev) && b + units == next) {
449			units += slob_units(next);
450			set_slob(b, units, slob_next(next));
451		} else
452			set_slob(b, units, next);
453
454		if (prev + slob_units(prev) == b) {
455			units = slob_units(b) + slob_units(prev);
456			set_slob(prev, units, slob_next(b));
457		} else
458			set_slob(prev, slob_units(prev), b);
459	}
460out:
461	spin_unlock_irqrestore(&slob_lock, flags);
462}
463
464/*
465 * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
466 */
467
468static __always_inline void *
469__do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller)
470{
471	unsigned int *m;
472	int minalign = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
473	void *ret;
474
475	gfp &= gfp_allowed_mask;
476
477	fs_reclaim_acquire(gfp);
478	fs_reclaim_release(gfp);
479
480	if (size < PAGE_SIZE - minalign) {
481		int align = minalign;
482
483		/*
484		 * For power of two sizes, guarantee natural alignment for
485		 * kmalloc()'d objects.
486		 */
487		if (is_power_of_2(size))
488			align = max(minalign, (int) size);
489
 
490		if (!size)
491			return ZERO_SIZE_PTR;
492
493		m = slob_alloc(size + minalign, gfp, align, node, minalign);
494
495		if (!m)
496			return NULL;
497		*m = size;
498		ret = (void *)m + minalign;
499
500		trace_kmalloc_node(caller, ret,
501				   size, size + minalign, 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
509		trace_kmalloc_node(caller, ret,
510				   size, PAGE_SIZE << order, gfp, node);
511	}
512
513	kmemleak_alloc(ret, size, 1, gfp);
514	return ret;
515}
516
517void *__kmalloc(size_t size, gfp_t gfp)
518{
519	return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, _RET_IP_);
520}
521EXPORT_SYMBOL(__kmalloc);
522
523void *__kmalloc_track_caller(size_t size, gfp_t gfp, unsigned long caller)
524{
525	return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, caller);
526}
527EXPORT_SYMBOL(__kmalloc_track_caller);
528
529#ifdef CONFIG_NUMA
530void *__kmalloc_node_track_caller(size_t size, gfp_t gfp,
531					int node, unsigned long caller)
532{
533	return __do_kmalloc_node(size, gfp, node, caller);
534}
535EXPORT_SYMBOL(__kmalloc_node_track_caller);
536#endif
537
538void kfree(const void *block)
539{
540	struct page *sp;
541
542	trace_kfree(_RET_IP_, block);
543
544	if (unlikely(ZERO_OR_NULL_PTR(block)))
545		return;
546	kmemleak_free(block);
547
548	sp = virt_to_page(block);
549	if (PageSlab(sp)) {
550		int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
551		unsigned int *m = (unsigned int *)(block - align);
552		slob_free(m, *m + align);
553	} else {
554		unsigned int order = compound_order(sp);
555		mod_node_page_state(page_pgdat(sp), NR_SLAB_UNRECLAIMABLE_B,
556				    -(PAGE_SIZE << order));
557		__free_pages(sp, order);
558
559	}
560}
561EXPORT_SYMBOL(kfree);
562
563/* can't use ksize for kmem_cache_alloc memory, only kmalloc */
564size_t __ksize(const void *block)
565{
566	struct page *sp;
567	int align;
568	unsigned int *m;
569
570	BUG_ON(!block);
571	if (unlikely(block == ZERO_SIZE_PTR))
572		return 0;
573
574	sp = virt_to_page(block);
575	if (unlikely(!PageSlab(sp)))
576		return page_size(sp);
 
 
 
 
 
 
577
578	align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
579	m = (unsigned int *)(block - align);
580	return SLOB_UNITS(*m) * SLOB_UNIT;
581}
582EXPORT_SYMBOL(__ksize);
 
583
584int __kmem_cache_create(struct kmem_cache *c, slab_flags_t flags)
 
585{
586	if (flags & SLAB_TYPESAFE_BY_RCU) {
587		/* leave room for rcu footer at the end of object */
588		c->size += sizeof(struct slob_rcu);
589	}
590	c->flags = flags;
591	return 0;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
592}
 
593
594static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
595{
596	void *b;
597
598	flags &= gfp_allowed_mask;
599
600	fs_reclaim_acquire(flags);
601	fs_reclaim_release(flags);
602
603	if (c->size < PAGE_SIZE) {
604		b = slob_alloc(c->size, flags, c->align, node, 0);
605		trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size,
606					    SLOB_UNITS(c->size) * SLOB_UNIT,
607					    flags, node);
608	} else {
609		b = slob_new_pages(flags, get_order(c->size), node);
610		trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size,
611					    PAGE_SIZE << get_order(c->size),
612					    flags, node);
613	}
614
615	if (b && c->ctor) {
616		WARN_ON_ONCE(flags & __GFP_ZERO);
617		c->ctor(b);
618	}
619
620	kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
621	return b;
622}
623
624void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
625{
626	return slob_alloc_node(cachep, flags, NUMA_NO_NODE);
627}
628EXPORT_SYMBOL(kmem_cache_alloc);
629
630#ifdef CONFIG_NUMA
631void *__kmalloc_node(size_t size, gfp_t gfp, int node)
632{
633	return __do_kmalloc_node(size, gfp, node, _RET_IP_);
634}
635EXPORT_SYMBOL(__kmalloc_node);
636
637void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t gfp, int node)
638{
639	return slob_alloc_node(cachep, gfp, node);
640}
641EXPORT_SYMBOL(kmem_cache_alloc_node);
642#endif
643
644static void __kmem_cache_free(void *b, int size)
645{
646	if (size < PAGE_SIZE)
647		slob_free(b, size);
648	else
649		slob_free_pages(b, get_order(size));
650}
651
652static void kmem_rcu_free(struct rcu_head *head)
653{
654	struct slob_rcu *slob_rcu = (struct slob_rcu *)head;
655	void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));
656
657	__kmem_cache_free(b, slob_rcu->size);
658}
659
660void kmem_cache_free(struct kmem_cache *c, void *b)
661{
662	kmemleak_free_recursive(b, c->flags);
663	if (unlikely(c->flags & SLAB_TYPESAFE_BY_RCU)) {
664		struct slob_rcu *slob_rcu;
665		slob_rcu = b + (c->size - sizeof(struct slob_rcu));
666		slob_rcu->size = c->size;
667		call_rcu(&slob_rcu->head, kmem_rcu_free);
668	} else {
669		__kmem_cache_free(b, c->size);
670	}
671
672	trace_kmem_cache_free(_RET_IP_, b);
673}
674EXPORT_SYMBOL(kmem_cache_free);
675
676void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
677{
678	__kmem_cache_free_bulk(s, size, p);
679}
680EXPORT_SYMBOL(kmem_cache_free_bulk);
681
682int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
683								void **p)
684{
685	return __kmem_cache_alloc_bulk(s, flags, size, p);
686}
687EXPORT_SYMBOL(kmem_cache_alloc_bulk);
688
689int __kmem_cache_shutdown(struct kmem_cache *c)
690{
691	/* No way to check for remaining objects */
692	return 0;
693}
 
694
695void __kmem_cache_release(struct kmem_cache *c)
696{
697}
698
699int __kmem_cache_shrink(struct kmem_cache *d)
700{
701	return 0;
702}
703
704struct kmem_cache kmem_cache_boot = {
705	.name = "kmem_cache",
706	.size = sizeof(struct kmem_cache),
707	.flags = SLAB_PANIC,
708	.align = ARCH_KMALLOC_MINALIGN,
709};
710
711void __init kmem_cache_init(void)
712{
713	kmem_cache = &kmem_cache_boot;
714	slab_state = UP;
715}
716
717void __init kmem_cache_init_late(void)
718{
719	slab_state = FULL;
720}