percpu: remove rbtree and use page->index instead

 * Allocation is done in offset-size areas of single unit space.  Ie,

 * an area of 512 bytes at 6k in c1 occupies 512 bytes at 6k of c1:u0,

 * c1:u1, c1:u2 and c1:u3.  Percpu access can be done by configuring

 * percpu base registers UNIT_SIZE apart.

 * percpu base registers pcpu_unit_size apart.

 *

 * There are usually many small percpu allocations many of them as

 * small as 4 bytes.  The allocator organizes chunks into lists

 * region and negative allocated.  Allocation inside a chunk is done

 * by scanning this map sequentially and serving the first matching

 * entry.  This is mostly copied from the percpu_modalloc() allocator.

 * Chunks are also linked into a rb tree to ease address to chunk

 * mapping during free.

 * Chunks can be determined from the address using the index field

 * in the page struct. The index field contains a pointer to the chunk.

 *

 * To use this allocator, arch code should do the followings.

 *

#include <linux/mutex.h>

#include <linux/percpu.h>

#include <linux/pfn.h>

#include <linux/rbtree.h>

#include <linux/slab.h>

#include <linux/spinlock.h>

#include <linux/vmalloc.h>

struct pcpu_chunk {

	struct list_head	list;		/* linked to pcpu_slot lists */

	struct rb_node		rb_node;	/* key is chunk->vm->addr */

	int			free_size;	/* free bytes in the chunk */

	int			contig_hint;	/* max contiguous size hint */

	struct vm_struct	*vm;		/* mapped vmalloc region */

 * There are two locks - pcpu_alloc_mutex and pcpu_lock.  The former

 * protects allocation/reclaim paths, chunks and chunk->page arrays.

 * The latter is a spinlock and protects the index data structures -

 * chunk slots, rbtree, chunks and area maps in chunks.

 * chunk slots, chunks and area maps in chunks.

 *

 * During allocation, pcpu_alloc_mutex is kept locked all the time and

 * pcpu_lock is grabbed and released as necessary.  All actual memory

static DEFINE_SPINLOCK(pcpu_lock);	/* protects index data structures */

static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */

static struct rb_root pcpu_addr_root = RB_ROOT;	/* chunks by address */

/* reclaim work to release fully free chunks, scheduled from free path */

static void pcpu_reclaim(struct work_struct *work);

	return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;

}

/* set the pointer to a chunk in a page struct */

static void pcpu_set_page_chunk(struct page *page, struct pcpu_chunk *pcpu)

{

	page->index = (unsigned long)pcpu;

}

/* obtain pointer to a chunk from a page struct */

static struct pcpu_chunk *pcpu_get_page_chunk(struct page *page)

{

	return (struct pcpu_chunk *)page->index;

}

/**

 * pcpu_mem_alloc - allocate memory

 * @size: bytes to allocate

	}

}

static struct rb_node **pcpu_chunk_rb_search(void *addr,

					     struct rb_node **parentp)

{

	struct rb_node **p = &pcpu_addr_root.rb_node;

	struct rb_node *parent = NULL;

	struct pcpu_chunk *chunk;

	while (*p) {

		parent = *p;

		chunk = rb_entry(parent, struct pcpu_chunk, rb_node);

		if (addr < chunk->vm->addr)

			p = &(*p)->rb_left;

		else if (addr > chunk->vm->addr)

			p = &(*p)->rb_right;

		else

			break;

	}

	if (parentp)

		*parentp = parent;

	return p;

}

/**

 * pcpu_chunk_addr_search - search for chunk containing specified address

 * @addr: address to search for

 *

 * Look for chunk which might contain @addr.  More specifically, it

 * searchs for the chunk with the highest start address which isn't

 * beyond @addr.

 *

 * CONTEXT:

 * pcpu_lock.

 * pcpu_chunk_addr_search - determine chunk containing specified address

 * @addr: address for which the chunk needs to be determined.

 *

 * RETURNS:

 * The address of the found chunk.

static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)

{

	void *first_start = pcpu_first_chunk->vm->addr;

	struct rb_node *n, *parent;

	struct pcpu_chunk *chunk;

	/* is it in the first chunk? */

	if (addr >= first_start && addr < first_start + pcpu_chunk_size) {

		return pcpu_first_chunk;

	}

	/* nah... search the regular ones */

	n = *pcpu_chunk_rb_search(addr, &parent);

	if (!n) {

		/* no exactly matching chunk, the parent is the closest */

		n = parent;

		BUG_ON(!n);

	}

	chunk = rb_entry(n, struct pcpu_chunk, rb_node);

	if (addr < chunk->vm->addr) {

		/* the parent was the next one, look for the previous one */

		n = rb_prev(n);

		BUG_ON(!n);

		chunk = rb_entry(n, struct pcpu_chunk, rb_node);

	}

	return chunk;

}

/**

 * pcpu_chunk_addr_insert - insert chunk into address rb tree

 * @new: chunk to insert

 *

 * Insert @new into address rb tree.

 *

 * CONTEXT:

 * pcpu_lock.

 */

static void pcpu_chunk_addr_insert(struct pcpu_chunk *new)

{

	struct rb_node **p, *parent;

	p = pcpu_chunk_rb_search(new->vm->addr, &parent);

	BUG_ON(*p);

	rb_link_node(&new->rb_node, parent, p);

	rb_insert_color(&new->rb_node, &pcpu_addr_root);

	return pcpu_get_page_chunk(vmalloc_to_page(addr));

}

/**

						  alloc_mask, 0);

			if (!*pagep)

				goto err;

			pcpu_set_page_chunk(*pagep, chunk);

		}

	}

	spin_lock_irq(&pcpu_lock);

	pcpu_chunk_relocate(chunk, -1);

	pcpu_chunk_addr_insert(chunk);

	goto restart;

area_found:

		if (chunk == list_first_entry(head, struct pcpu_chunk, list))

			continue;

		rb_erase(&chunk->rb_node, &pcpu_addr_root);

		list_move(&chunk->list, &todo);

	}