/*
   * 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 PageSlab()
   * 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_exact_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 page *sp)
  {
  	return PageSlobFree(sp);
  }
  
  static void set_slob_page_free(struct page *sp, struct list_head *list)
  {
  	list_add(&sp->list, list);
  	__SetPageSlobFree(sp);
  }
  
  static inline void clear_slob_page_free(struct page *sp)
  {
  	list_del(&sp->list);
  	__ClearPageSlobFree(sp);
  }
  
  #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_DESTROY_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)
  {
  	void *page;
  
  #ifdef CONFIG_NUMA
  	if (node != NUMA_NO_NODE)
  		page = alloc_pages_exact_node(node, gfp, order);
  	else
  #endif
  		page = alloc_pages(gfp, order);
  
  	if (!page)
  		return NULL;
  
  	return page_address(page);
  }
  
  static void slob_free_pages(void *b, int order)
  {
  	if (current->reclaim_state)
  		current->reclaim_state->reclaimed_slab += 1 << order;
  	free_pages((unsigned long)b, order);
  }
  
  /*
   * Allocate a slob block within a given slob_page sp.
   */
  static void *slob_page_alloc(struct page *sp, size_t size, int align)
  {
  	slob_t *prev, *cur, *aligned = NULL;
  	int delta = 0, units = SLOB_UNITS(size);
  
  	for (prev = NULL, cur = sp->freelist; ; prev = cur, cur = slob_next(cur)) {
  		slobidx_t avail = slob_units(cur);
  
  		if (align) {
  			aligned = (slob_t *)ALIGN((unsigned long)cur, align);
  			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);
  			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)
  {
  	struct page *sp;
  	struct list_head *prev;
  	struct list_head *slob_list;
  	slob_t *b = NULL;
  	unsigned long flags;
  
  	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, list) {
  #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 && page_to_nid(sp) != node)
  			continue;
  #endif
  		/* Enough room on this page? */
  		if (sp->units < SLOB_UNITS(size))
  			continue;
  
  		/* Attempt to alloc */
  		prev = sp->list.prev;
  		b = slob_page_alloc(sp, size, align);
  		if (!b)
  			continue;
  
  		/* 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 (prev != slob_list->prev &&
  				slob_list->next != prev->next)
  			list_move_tail(slob_list, prev->next);
  		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;
  		sp = virt_to_page(b);
  		__SetPageSlab(sp);
  
  		spin_lock_irqsave(&slob_lock, flags);
  		sp->units = SLOB_UNITS(PAGE_SIZE);
  		sp->freelist = b;
  		INIT_LIST_HEAD(&sp->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);
  		BUG_ON(!b);
  		spin_unlock_irqrestore(&slob_lock, flags);
  	}
  	if (unlikely((gfp & __GFP_ZERO) && b))
  		memset(b, 0, size);
  	return b;
  }
  
  /*
   * slob_free: entry point into the slob allocator.
   */
  static void slob_free(void *block, int size)
  {
  	struct page *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_page(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);
  		__ClearPageSlab(sp);
  		page_mapcount_reset(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);
  }
  
  /*
   * 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;
  	int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
  	void *ret;
  
  	gfp &= gfp_allowed_mask;
  
  	lockdep_trace_alloc(gfp);
  
  	if (size < PAGE_SIZE - align) {
  		if (!size)
  			return ZERO_SIZE_PTR;
  
  		m = slob_alloc(size + align, gfp, align, node);
  
  		if (!m)
  			return NULL;
  		*m = size;
  		ret = (void *)m + align;
  
  		trace_kmalloc_node(caller, ret,
  				   size, size + align, gfp, node);
  	} else {
  		unsigned int order = get_order(size);
  
  		if (likely(order))
  			gfp |= __GFP_COMP;
  		ret = slob_new_pages(gfp, order, node);
  
  		trace_kmalloc_node(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);
  
  #ifdef CONFIG_TRACING
  void *__kmalloc_track_caller(size_t size, gfp_t gfp, unsigned long caller)
  {
  	return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, caller);
  }
  
  #ifdef CONFIG_NUMA
  void *__kmalloc_node_track_caller(size_t size, gfp_t gfp,
  					int node, unsigned long caller)
  {
  	return __do_kmalloc_node(size, gfp, node, caller);
  }
  #endif
  #endif
  
  void kfree(const void *block)
  {
  	struct page *sp;
  
  	trace_kfree(_RET_IP_, block);
  
  	if (unlikely(ZERO_OR_NULL_PTR(block)))
  		return;
  	kmemleak_free(block);
  
  	sp = virt_to_page(block);
  	if (PageSlab(sp)) {
  		int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
  		unsigned int *m = (unsigned int *)(block - align);
  		slob_free(m, *m + align);
  	} else
  		__free_pages(sp, compound_order(sp));
  }
  EXPORT_SYMBOL(kfree);
  
  /* can't use ksize for kmem_cache_alloc memory, only kmalloc */
  size_t ksize(const void *block)
  {
  	struct page *sp;
  	int align;
  	unsigned int *m;
  
  	BUG_ON(!block);
  	if (unlikely(block == ZERO_SIZE_PTR))
  		return 0;
  
  	sp = virt_to_page(block);
  	if (unlikely(!PageSlab(sp)))
  		return PAGE_SIZE << compound_order(sp);
  
  	align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
  	m = (unsigned int *)(block - align);
  	return SLOB_UNITS(*m) * SLOB_UNIT;
  }
  EXPORT_SYMBOL(ksize);
  
  int __kmem_cache_create(struct kmem_cache *c, unsigned long flags)
  {
  	if (flags & SLAB_DESTROY_BY_RCU) {
  		/* leave room for rcu footer at the end of object */
  		c->size += sizeof(struct slob_rcu);
  	}
  	c->flags = flags;
  	return 0;
  }
  
  void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
  {
  	void *b;
  
  	flags &= gfp_allowed_mask;
  
  	lockdep_trace_alloc(flags);
  
  	if (c->size < PAGE_SIZE) {
  		b = slob_alloc(c->size, flags, c->align, node);
  		trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size,
  					    SLOB_UNITS(c->size) * SLOB_UNIT,
  					    flags, node);
  	} else {
  		b = slob_new_pages(flags, get_order(c->size), node);
  		trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size,
  					    PAGE_SIZE << get_order(c->size),
  					    flags, node);
  	}
  
  	if (b && c->ctor)
  		c->ctor(b);
  
  	kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
  	return b;
  }
  EXPORT_SYMBOL(slob_alloc_node);
  
  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);
  
  #ifdef CONFIG_NUMA
  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);
  #endif
  
  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);
  	if (unlikely(c->flags & SLAB_DESTROY_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);
  	}
  
  	trace_kmem_cache_free(_RET_IP_, b);
  }
  EXPORT_SYMBOL(kmem_cache_free);
  
  int __kmem_cache_shutdown(struct kmem_cache *c)
  {
  	/* No way to check for remaining objects */
  	return 0;
  }
  
  int kmem_cache_shrink(struct kmem_cache *d)
  {
  	return 0;
  }
  EXPORT_SYMBOL(kmem_cache_shrink);
  
  struct kmem_cache kmem_cache_boot = {
  	.name = "kmem_cache",
  	.size = sizeof(struct kmem_cache),
  	.flags = SLAB_PANIC,
  	.align = ARCH_KMALLOC_MINALIGN,
  };
  
  void __init kmem_cache_init(void)
  {
  	kmem_cache = &kmem_cache_boot;
  	slab_state = UP;
  }
  
  void __init kmem_cache_init_late(void)
  {
  	slab_state = FULL;
  }