mm/slob: remove slob.c

// SPDX-License-Identifier: GPL-2.0

/*

 * SLOB Allocator: Simple List Of Blocks

 *

 * Matt Mackall <mpm@selenic.com> 12/30/03

 *

 * NUMA support by Paul Mundt, 2007.

 *

 * How SLOB works:

 *

 * The core of SLOB is a traditional K&R style heap allocator, with

 * support for returning aligned objects. The granularity of this

 * allocator is as little as 2 bytes, however typically most architectures

 * will require 4 bytes on 32-bit and 8 bytes on 64-bit.

 *

 * The slob heap is a set of linked list of pages from alloc_pages(),

 * and within each page, there is a singly-linked list of free blocks

 * (slob_t). The heap is grown on demand. To reduce fragmentation,

 * heap pages are segregated into three lists, with objects less than

 * 256 bytes, objects less than 1024 bytes, and all other objects.

 *

 * Allocation from heap involves first searching for a page with

 * sufficient free blocks (using a next-fit-like approach) followed by

 * a first-fit scan of the page. Deallocation inserts objects back

 * into the free list in address order, so this is effectively an

 * address-ordered first fit.

 *

 * Above this is an implementation of kmalloc/kfree. Blocks returned

 * from kmalloc are prepended with a 4-byte header with the kmalloc size.

 * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls

 * alloc_pages() directly, allocating compound pages so the page order

 * does not have to be separately tracked.

 * These objects are detected in kfree() because folio_test_slab()

 * is false for them.

 *

 * SLAB is emulated on top of SLOB by simply calling constructors and

 * destructors for every SLAB allocation. Objects are returned with the

 * 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which

 * case the low-level allocator will fragment blocks to create the proper

 * alignment. Again, objects of page-size or greater are allocated by

 * calling alloc_pages(). As SLAB objects know their size, no separate

 * size bookkeeping is necessary and there is essentially no allocation

 * space overhead, and compound pages aren't needed for multi-page

 * allocations.

 *

 * NUMA support in SLOB is fairly simplistic, pushing most of the real

 * logic down to the page allocator, and simply doing the node accounting

 * on the upper levels. In the event that a node id is explicitly

 * provided, __alloc_pages_node() with the specified node id is used

 * instead. The common case (or when the node id isn't explicitly provided)

 * will default to the current node, as per numa_node_id().

 *

 * Node aware pages are still inserted in to the global freelist, and

 * these are scanned for by matching against the node id encoded in the

 * page flags. As a result, block allocations that can be satisfied from

 * the freelist will only be done so on pages residing on the same node,

 * in order to prevent random node placement.

 */

#include <linux/kernel.h>

#include <linux/slab.h>

#include <linux/mm.h>

#include <linux/swap.h> /* struct reclaim_state */

#include <linux/cache.h>

#include <linux/init.h>

#include <linux/export.h>

#include <linux/rcupdate.h>

#include <linux/list.h>

#include <linux/kmemleak.h>

#include <trace/events/kmem.h>

#include <linux/atomic.h>

#include "slab.h"

/*

 * slob_block has a field 'units', which indicates size of block if +ve,

 * or offset of next block if -ve (in SLOB_UNITs).

 *

 * Free blocks of size 1 unit simply contain the offset of the next block.

 * Those with larger size contain their size in the first SLOB_UNIT of

 * memory, and the offset of the next free block in the second SLOB_UNIT.

 */

#if PAGE_SIZE <= (32767 * 2)

typedef s16 slobidx_t;

#else

typedef s32 slobidx_t;

#endif

struct slob_block {

	slobidx_t units;

};

typedef struct slob_block slob_t;

/*

 * All partially free slob pages go on these lists.

 */

#define SLOB_BREAK1 256

#define SLOB_BREAK2 1024

static LIST_HEAD(free_slob_small);

static LIST_HEAD(free_slob_medium);

static LIST_HEAD(free_slob_large);

/*

 * slob_page_free: true for pages on free_slob_pages list.

 */

static inline int slob_page_free(struct slab *slab)

{

	return PageSlobFree(slab_page(slab));

}

static void set_slob_page_free(struct slab *slab, struct list_head *list)

{

	list_add(&slab->slab_list, list);

	__SetPageSlobFree(slab_page(slab));

}

static inline void clear_slob_page_free(struct slab *slab)

{

	list_del(&slab->slab_list);

	__ClearPageSlobFree(slab_page(slab));

}

#define SLOB_UNIT sizeof(slob_t)

#define SLOB_UNITS(size) DIV_ROUND_UP(size, SLOB_UNIT)

/*

 * struct slob_rcu is inserted at the tail of allocated slob blocks, which

 * were created with a SLAB_TYPESAFE_BY_RCU slab. slob_rcu is used to free

 * the block using call_rcu.

 */

struct slob_rcu {

	struct rcu_head head;

	int size;

};

/*

 * slob_lock protects all slob allocator structures.

 */

static DEFINE_SPINLOCK(slob_lock);

/*

 * Encode the given size and next info into a free slob block s.

 */

static void set_slob(slob_t *s, slobidx_t size, slob_t *next)

{

	slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);

	slobidx_t offset = next - base;

	if (size > 1) {

		s[0].units = size;

		s[1].units = offset;

	} else

		s[0].units = -offset;

}

/*

 * Return the size of a slob block.

 */

static slobidx_t slob_units(slob_t *s)

{

	if (s->units > 0)

		return s->units;

	return 1;

}

/*

 * Return the next free slob block pointer after this one.

 */

static slob_t *slob_next(slob_t *s)

{

	slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);

	slobidx_t next;

	if (s[0].units < 0)

		next = -s[0].units;

	else

		next = s[1].units;

	return base+next;

}

/*

 * Returns true if s is the last free block in its page.

 */

static int slob_last(slob_t *s)

{

	return !((unsigned long)slob_next(s) & ~PAGE_MASK);

}

static void *slob_new_pages(gfp_t gfp, int order, int node)

{

	struct page *page;

#ifdef CONFIG_NUMA

	if (node != NUMA_NO_NODE)

		page = __alloc_pages_node(node, gfp, order);

	else

#endif

		page = alloc_pages(gfp, order);

	if (!page)

		return NULL;

	mod_node_page_state(page_pgdat(page), NR_SLAB_UNRECLAIMABLE_B,

			    PAGE_SIZE << order);

	return page_address(page);

}

static void slob_free_pages(void *b, int order)

{

	struct page *sp = virt_to_page(b);

	if (current->reclaim_state)

		current->reclaim_state->reclaimed_slab += 1 << order;

	mod_node_page_state(page_pgdat(sp), NR_SLAB_UNRECLAIMABLE_B,

			    -(PAGE_SIZE << order));

	__free_pages(sp, order);

}

/*

 * slob_page_alloc() - Allocate a slob block within a given slob_page sp.

 * @sp: Page to look in.

 * @size: Size of the allocation.

 * @align: Allocation alignment.

 * @align_offset: Offset in the allocated block that will be aligned.

 * @page_removed_from_list: Return parameter.

 *

 * Tries to find a chunk of memory at least @size bytes big within @page.

 *

 * Return: Pointer to memory if allocated, %NULL otherwise.  If the

 *         allocation fills up @page then the page is removed from the

 *         freelist, in this case @page_removed_from_list will be set to

 *         true (set to false otherwise).

 */

static void *slob_page_alloc(struct slab *sp, size_t size, int align,

			      int align_offset, bool *page_removed_from_list)

{

	slob_t *prev, *cur, *aligned = NULL;

	int delta = 0, units = SLOB_UNITS(size);

	*page_removed_from_list = false;

	for (prev = NULL, cur = sp->freelist; ; prev = cur, cur = slob_next(cur)) {

		slobidx_t avail = slob_units(cur);

		/*

		 * 'aligned' will hold the address of the slob block so that the

		 * address 'aligned'+'align_offset' is aligned according to the

		 * 'align' parameter. This is for kmalloc() which prepends the

		 * allocated block with its size, so that the block itself is

		 * aligned when needed.

		 */

		if (align) {

			aligned = (slob_t *)

				(ALIGN((unsigned long)cur + align_offset, align)

				 - align_offset);

			delta = aligned - cur;

		}

		if (avail >= units + delta) { /* room enough? */

			slob_t *next;

			if (delta) { /* need to fragment head to align? */

				next = slob_next(cur);

				set_slob(aligned, avail - delta, next);

				set_slob(cur, delta, aligned);

				prev = cur;

				cur = aligned;

				avail = slob_units(cur);

			}

			next = slob_next(cur);

			if (avail == units) { /* exact fit? unlink. */

				if (prev)

					set_slob(prev, slob_units(prev), next);

				else

					sp->freelist = next;

			} else { /* fragment */

				if (prev)

					set_slob(prev, slob_units(prev), cur + units);

				else

					sp->freelist = cur + units;

				set_slob(cur + units, avail - units, next);

			}

			sp->units -= units;

			if (!sp->units) {

				clear_slob_page_free(sp);

				*page_removed_from_list = true;

			}

			return cur;

		}

		if (slob_last(cur))

			return NULL;

	}

}

/*

 * slob_alloc: entry point into the slob allocator.

 */

static void *slob_alloc(size_t size, gfp_t gfp, int align, int node,

							int align_offset)

{

	struct folio *folio;

	struct slab *sp;

	struct list_head *slob_list;

	slob_t *b = NULL;

	unsigned long flags;

	bool _unused;

	if (size < SLOB_BREAK1)

		slob_list = &free_slob_small;

	else if (size < SLOB_BREAK2)

		slob_list = &free_slob_medium;

	else

		slob_list = &free_slob_large;

	spin_lock_irqsave(&slob_lock, flags);

	/* Iterate through each partially free page, try to find room */

	list_for_each_entry(sp, slob_list, slab_list) {

		bool page_removed_from_list = false;

#ifdef CONFIG_NUMA

		/*

		 * If there's a node specification, search for a partial

		 * page with a matching node id in the freelist.

		 */

		if (node != NUMA_NO_NODE && slab_nid(sp) != node)

			continue;

#endif

		/* Enough room on this page? */

		if (sp->units < SLOB_UNITS(size))

			continue;

		b = slob_page_alloc(sp, size, align, align_offset, &page_removed_from_list);

		if (!b)

			continue;

		/*

		 * If slob_page_alloc() removed sp from the list then we

		 * cannot call list functions on sp.  If so allocation

		 * did not fragment the page anyway so optimisation is

		 * unnecessary.

		 */

		if (!page_removed_from_list) {

			/*

			 * Improve fragment distribution and reduce our average

			 * search time by starting our next search here. (see

			 * Knuth vol 1, sec 2.5, pg 449)

			 */

			if (!list_is_first(&sp->slab_list, slob_list))

				list_rotate_to_front(&sp->slab_list, slob_list);

		}

		break;

	}

	spin_unlock_irqrestore(&slob_lock, flags);

	/* Not enough space: must allocate a new page */

	if (!b) {

		b = slob_new_pages(gfp & ~__GFP_ZERO, 0, node);

		if (!b)

			return NULL;

		folio = virt_to_folio(b);

		__folio_set_slab(folio);

		sp = folio_slab(folio);

		spin_lock_irqsave(&slob_lock, flags);

		sp->units = SLOB_UNITS(PAGE_SIZE);

		sp->freelist = b;

		INIT_LIST_HEAD(&sp->slab_list);

		set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));

		set_slob_page_free(sp, slob_list);

		b = slob_page_alloc(sp, size, align, align_offset, &_unused);

		BUG_ON(!b);

		spin_unlock_irqrestore(&slob_lock, flags);

	}

	if (unlikely(gfp & __GFP_ZERO))

		memset(b, 0, size);

	return b;

}

/*

 * slob_free: entry point into the slob allocator.

 */

static void slob_free(void *block, int size)

{

	struct slab *sp;

	slob_t *prev, *next, *b = (slob_t *)block;

	slobidx_t units;

	unsigned long flags;

	struct list_head *slob_list;

	if (unlikely(ZERO_OR_NULL_PTR(block)))

		return;

	BUG_ON(!size);

	sp = virt_to_slab(block);

	units = SLOB_UNITS(size);

	spin_lock_irqsave(&slob_lock, flags);

	if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {

		/* Go directly to page allocator. Do not pass slob allocator */

		if (slob_page_free(sp))

			clear_slob_page_free(sp);

		spin_unlock_irqrestore(&slob_lock, flags);

		__folio_clear_slab(slab_folio(sp));

		slob_free_pages(b, 0);

		return;

	}

	if (!slob_page_free(sp)) {

		/* This slob page is about to become partially free. Easy! */

		sp->units = units;

		sp->freelist = b;

		set_slob(b, units,

			(void *)((unsigned long)(b +

					SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));

		if (size < SLOB_BREAK1)

			slob_list = &free_slob_small;

		else if (size < SLOB_BREAK2)

			slob_list = &free_slob_medium;

		else

			slob_list = &free_slob_large;

		set_slob_page_free(sp, slob_list);

		goto out;

	}

	/*

	 * Otherwise the page is already partially free, so find reinsertion

	 * point.

	 */

	sp->units += units;

	if (b < (slob_t *)sp->freelist) {

		if (b + units == sp->freelist) {

			units += slob_units(sp->freelist);

			sp->freelist = slob_next(sp->freelist);

		}

		set_slob(b, units, sp->freelist);

		sp->freelist = b;

	} else {

		prev = sp->freelist;

		next = slob_next(prev);

		while (b > next) {

			prev = next;

			next = slob_next(prev);

		}

		if (!slob_last(prev) && b + units == next) {

			units += slob_units(next);

			set_slob(b, units, slob_next(next));

		} else

			set_slob(b, units, next);

		if (prev + slob_units(prev) == b) {

			units = slob_units(b) + slob_units(prev);

			set_slob(prev, units, slob_next(b));

		} else

			set_slob(prev, slob_units(prev), b);

	}

out:

	spin_unlock_irqrestore(&slob_lock, flags);

}

#ifdef CONFIG_PRINTK

void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)

{

	kpp->kp_ptr = object;

	kpp->kp_slab = slab;

}

#endif

/*

 * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.

 */

static __always_inline void *

__do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller)

{

	unsigned int *m;

	unsigned int minalign;

	void *ret;

	minalign = max_t(unsigned int, ARCH_KMALLOC_MINALIGN,

			 arch_slab_minalign());

	gfp &= gfp_allowed_mask;

	might_alloc(gfp);

	if (size < PAGE_SIZE - minalign) {

		int align = minalign;

		/*

		 * For power of two sizes, guarantee natural alignment for

		 * kmalloc()'d objects.

		 */

		if (is_power_of_2(size))

			align = max_t(unsigned int, minalign, size);

		if (!size)

			return ZERO_SIZE_PTR;

		m = slob_alloc(size + minalign, gfp, align, node, minalign);

		if (!m)

			return NULL;

		*m = size;

		ret = (void *)m + minalign;

		trace_kmalloc(caller, ret, size, size + minalign, gfp, node);

	} else {

		unsigned int order = get_order(size);

		if (likely(order))

			gfp |= __GFP_COMP;

		ret = slob_new_pages(gfp, order, node);

		trace_kmalloc(caller, ret, size, PAGE_SIZE << order, gfp, node);

	}

	kmemleak_alloc(ret, size, 1, gfp);

	return ret;

}

void *__kmalloc(size_t size, gfp_t gfp)

{

	return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, _RET_IP_);

}

EXPORT_SYMBOL(__kmalloc);

void *__kmalloc_node_track_caller(size_t size, gfp_t gfp,

					int node, unsigned long caller)

{

	return __do_kmalloc_node(size, gfp, node, caller);

}

EXPORT_SYMBOL(__kmalloc_node_track_caller);

void kfree(const void *block)

{

	struct folio *sp;

	trace_kfree(_RET_IP_, block);

	if (unlikely(ZERO_OR_NULL_PTR(block)))

		return;

	kmemleak_free(block);

	sp = virt_to_folio(block);

	if (folio_test_slab(sp)) {

		unsigned int align = max_t(unsigned int,

					   ARCH_KMALLOC_MINALIGN,

					   arch_slab_minalign());

		unsigned int *m = (unsigned int *)(block - align);

		slob_free(m, *m + align);

	} else {

		unsigned int order = folio_order(sp);

		mod_node_page_state(folio_pgdat(sp), NR_SLAB_UNRECLAIMABLE_B,

				    -(PAGE_SIZE << order));

		__free_pages(folio_page(sp, 0), order);

	}

}

EXPORT_SYMBOL(kfree);

size_t kmalloc_size_roundup(size_t size)

{

	/* Short-circuit the 0 size case. */

	if (unlikely(size == 0))

		return 0;

	/* Short-circuit saturated "too-large" case. */

	if (unlikely(size == SIZE_MAX))

		return SIZE_MAX;

	return ALIGN(size, ARCH_KMALLOC_MINALIGN);

}

EXPORT_SYMBOL(kmalloc_size_roundup);

/* can't use ksize for kmem_cache_alloc memory, only kmalloc */

size_t __ksize(const void *block)

{

	struct folio *folio;

	unsigned int align;

	unsigned int *m;

	BUG_ON(!block);

	if (unlikely(block == ZERO_SIZE_PTR))

		return 0;

	folio = virt_to_folio(block);

	if (unlikely(!folio_test_slab(folio)))

		return folio_size(folio);

	align = max_t(unsigned int, ARCH_KMALLOC_MINALIGN,

		      arch_slab_minalign());

	m = (unsigned int *)(block - align);

	return SLOB_UNITS(*m) * SLOB_UNIT;

}

int __kmem_cache_create(struct kmem_cache *c, slab_flags_t flags)

{

	if (flags & SLAB_TYPESAFE_BY_RCU) {

		/* leave room for rcu footer at the end of object */

		c->size += sizeof(struct slob_rcu);

	}

	/* Actual size allocated */

	c->size = SLOB_UNITS(c->size) * SLOB_UNIT;

	c->flags = flags;

	return 0;

}

static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node)

{

	void *b;

	flags &= gfp_allowed_mask;

	might_alloc(flags);

	if (c->size < PAGE_SIZE) {

		b = slob_alloc(c->size, flags, c->align, node, 0);

		trace_kmem_cache_alloc(_RET_IP_, b, c, flags, node);

	} else {

		b = slob_new_pages(flags, get_order(c->size), node);

		trace_kmem_cache_alloc(_RET_IP_, b, c, flags, node);

	}

	if (b && c->ctor) {

		WARN_ON_ONCE(flags & __GFP_ZERO);

		c->ctor(b);

	}

	kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);

	return b;

}

void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)

{

	return slob_alloc_node(cachep, flags, NUMA_NO_NODE);

}

EXPORT_SYMBOL(kmem_cache_alloc);

void *kmem_cache_alloc_lru(struct kmem_cache *cachep, struct list_lru *lru, gfp_t flags)

{

	return slob_alloc_node(cachep, flags, NUMA_NO_NODE);

}

EXPORT_SYMBOL(kmem_cache_alloc_lru);

void *__kmalloc_node(size_t size, gfp_t gfp, int node)

{

	return __do_kmalloc_node(size, gfp, node, _RET_IP_);

}

EXPORT_SYMBOL(__kmalloc_node);

void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t gfp, int node)

{

	return slob_alloc_node(cachep, gfp, node);

}

EXPORT_SYMBOL(kmem_cache_alloc_node);

static void __kmem_cache_free(void *b, int size)

{

	if (size < PAGE_SIZE)

		slob_free(b, size);

	else

		slob_free_pages(b, get_order(size));

}

static void kmem_rcu_free(struct rcu_head *head)

{

	struct slob_rcu *slob_rcu = (struct slob_rcu *)head;

	void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));

	__kmem_cache_free(b, slob_rcu->size);

}

void kmem_cache_free(struct kmem_cache *c, void *b)

{

	kmemleak_free_recursive(b, c->flags);

	trace_kmem_cache_free(_RET_IP_, b, c);

	if (unlikely(c->flags & SLAB_TYPESAFE_BY_RCU)) {

		struct slob_rcu *slob_rcu;

		slob_rcu = b + (c->size - sizeof(struct slob_rcu));

		slob_rcu->size = c->size;

		call_rcu(&slob_rcu->head, kmem_rcu_free);

	} else {

		__kmem_cache_free(b, c->size);

	}

}

EXPORT_SYMBOL(kmem_cache_free);

void kmem_cache_free_bulk(struct kmem_cache *s, size_t nr, void **p)

{

	size_t i;

	for (i = 0; i < nr; i++) {

		if (s)

			kmem_cache_free(s, p[i]);

		else

			kfree(p[i]);

	}

}

EXPORT_SYMBOL(kmem_cache_free_bulk);

int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr,

								void **p)

{

	size_t i;

	for (i = 0; i < nr; i++) {

		void *x = p[i] = kmem_cache_alloc(s, flags);

		if (!x) {

			kmem_cache_free_bulk(s, i, p);

			return 0;