/*
   * mm/percpu-vm.c - vmalloc area based chunk allocation
   *
   * Copyright (C) 2010		SUSE Linux Products GmbH
   * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
   *
   * This file is released under the GPLv2.
   *
   * Chunks are mapped into vmalloc areas and populated page by page.
   * This is the default chunk allocator.
   */
  
  static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk,
  				    unsigned int cpu, int page_idx)
  {
  	/* must not be used on pre-mapped chunk */
  	WARN_ON(chunk->immutable);
  
  	return vmalloc_to_page((void *)pcpu_chunk_addr(chunk, cpu, page_idx));
  }
  
  /**

   * pcpu_get_pages - get temp pages array

   * @chunk: chunk of interest

   *

   * Returns pointer to array of pointers to struct page which can be indexed

   * with pcpu_page_idx().  Note that there is only one array and accesses
   * should be serialized by pcpu_alloc_mutex.

   *
   * RETURNS:

   * Pointer to temp pages array on success.

   */

  static struct page **pcpu_get_pages(struct pcpu_chunk *chunk_alloc)

  {
  	static struct page **pages;

  	size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);

  	lockdep_assert_held(&pcpu_alloc_mutex);
  
  	if (!pages)

  		pages = pcpu_mem_zalloc(pages_size);

  	return pages;
  }
  
  /**
   * pcpu_free_pages - free pages which were allocated for @chunk
   * @chunk: chunk pages were allocated for
   * @pages: array of pages to be freed, indexed by pcpu_page_idx()

   * @page_start: page index of the first page to be freed
   * @page_end: page index of the last page to be freed + 1
   *
   * Free pages [@page_start and @page_end) in @pages for all units.
   * The pages were allocated for @chunk.
   */
  static void pcpu_free_pages(struct pcpu_chunk *chunk,

  			    struct page **pages, int page_start, int page_end)

  {
  	unsigned int cpu;
  	int i;
  
  	for_each_possible_cpu(cpu) {
  		for (i = page_start; i < page_end; i++) {
  			struct page *page = pages[pcpu_page_idx(cpu, i)];
  
  			if (page)
  				__free_page(page);
  		}
  	}
  }
  
  /**
   * pcpu_alloc_pages - allocates pages for @chunk
   * @chunk: target chunk
   * @pages: array to put the allocated pages into, indexed by pcpu_page_idx()

   * @page_start: page index of the first page to be allocated
   * @page_end: page index of the last page to be allocated + 1
   *
   * Allocate pages [@page_start,@page_end) into @pages for all units.
   * The allocation is for @chunk.  Percpu core doesn't care about the
   * content of @pages and will pass it verbatim to pcpu_map_pages().
   */
  static int pcpu_alloc_pages(struct pcpu_chunk *chunk,

  			    struct page **pages, int page_start, int page_end)

  {
  	const gfp_t gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD;

  	unsigned int cpu, tcpu;

  	int i;
  
  	for_each_possible_cpu(cpu) {
  		for (i = page_start; i < page_end; i++) {
  			struct page **pagep = &pages[pcpu_page_idx(cpu, i)];
  
  			*pagep = alloc_pages_node(cpu_to_node(cpu), gfp, 0);

  			if (!*pagep)
  				goto err;

  		}
  	}
  	return 0;

  
  err:
  	while (--i >= page_start)
  		__free_page(pages[pcpu_page_idx(cpu, i)]);
  
  	for_each_possible_cpu(tcpu) {
  		if (tcpu == cpu)
  			break;
  		for (i = page_start; i < page_end; i++)
  			__free_page(pages[pcpu_page_idx(tcpu, i)]);
  	}
  	return -ENOMEM;

  }
  
  /**
   * pcpu_pre_unmap_flush - flush cache prior to unmapping
   * @chunk: chunk the regions to be flushed belongs to
   * @page_start: page index of the first page to be flushed
   * @page_end: page index of the last page to be flushed + 1
   *
   * Pages in [@page_start,@page_end) of @chunk are about to be
   * unmapped.  Flush cache.  As each flushing trial can be very
   * expensive, issue flush on the whole region at once rather than
   * doing it for each cpu.  This could be an overkill but is more
   * scalable.
   */
  static void pcpu_pre_unmap_flush(struct pcpu_chunk *chunk,
  				 int page_start, int page_end)
  {
  	flush_cache_vunmap(

  		pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
  		pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));

  }
  
  static void __pcpu_unmap_pages(unsigned long addr, int nr_pages)
  {
  	unmap_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT);
  }
  
  /**
   * pcpu_unmap_pages - unmap pages out of a pcpu_chunk
   * @chunk: chunk of interest
   * @pages: pages array which can be used to pass information to free

   * @page_start: page index of the first page to unmap
   * @page_end: page index of the last page to unmap + 1
   *
   * For each cpu, unmap pages [@page_start,@page_end) out of @chunk.
   * Corresponding elements in @pages were cleared by the caller and can
   * be used to carry information to pcpu_free_pages() which will be
   * called after all unmaps are finished.  The caller should call
   * proper pre/post flush functions.
   */
  static void pcpu_unmap_pages(struct pcpu_chunk *chunk,

  			     struct page **pages, int page_start, int page_end)

  {
  	unsigned int cpu;
  	int i;
  
  	for_each_possible_cpu(cpu) {
  		for (i = page_start; i < page_end; i++) {
  			struct page *page;
  
  			page = pcpu_chunk_page(chunk, cpu, i);
  			WARN_ON(!page);
  			pages[pcpu_page_idx(cpu, i)] = page;
  		}
  		__pcpu_unmap_pages(pcpu_chunk_addr(chunk, cpu, page_start),
  				   page_end - page_start);
  	}

  }
  
  /**
   * pcpu_post_unmap_tlb_flush - flush TLB after unmapping
   * @chunk: pcpu_chunk the regions to be flushed belong to
   * @page_start: page index of the first page to be flushed
   * @page_end: page index of the last page to be flushed + 1
   *
   * Pages [@page_start,@page_end) of @chunk have been unmapped.  Flush
   * TLB for the regions.  This can be skipped if the area is to be
   * returned to vmalloc as vmalloc will handle TLB flushing lazily.
   *
   * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
   * for the whole region.
   */
  static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
  				      int page_start, int page_end)
  {
  	flush_tlb_kernel_range(

  		pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
  		pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));

  }
  
  static int __pcpu_map_pages(unsigned long addr, struct page **pages,
  			    int nr_pages)
  {
  	return map_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT,
  					PAGE_KERNEL, pages);
  }
  
  /**
   * pcpu_map_pages - map pages into a pcpu_chunk
   * @chunk: chunk of interest
   * @pages: pages array containing pages to be mapped

   * @page_start: page index of the first page to map
   * @page_end: page index of the last page to map + 1
   *
   * For each cpu, map pages [@page_start,@page_end) into @chunk.  The
   * caller is responsible for calling pcpu_post_map_flush() after all
   * mappings are complete.
   *

   * This function is responsible for setting up whatever is necessary for
   * reverse lookup (addr -> chunk).

   */
  static int pcpu_map_pages(struct pcpu_chunk *chunk,

  			  struct page **pages, int page_start, int page_end)

  {
  	unsigned int cpu, tcpu;
  	int i, err;
  
  	for_each_possible_cpu(cpu) {
  		err = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),
  				       &pages[pcpu_page_idx(cpu, page_start)],
  				       page_end - page_start);
  		if (err < 0)
  			goto err;

  		for (i = page_start; i < page_end; i++)

  			pcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],
  					    chunk);

  	}

  	return 0;

  err:
  	for_each_possible_cpu(tcpu) {
  		if (tcpu == cpu)
  			break;
  		__pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
  				   page_end - page_start);
  	}

  	pcpu_post_unmap_tlb_flush(chunk, page_start, page_end);

  	return err;
  }
  
  /**
   * pcpu_post_map_flush - flush cache after mapping
   * @chunk: pcpu_chunk the regions to be flushed belong to
   * @page_start: page index of the first page to be flushed
   * @page_end: page index of the last page to be flushed + 1
   *
   * Pages [@page_start,@page_end) of @chunk have been mapped.  Flush
   * cache.
   *
   * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once
   * for the whole region.
   */
  static void pcpu_post_map_flush(struct pcpu_chunk *chunk,
  				int page_start, int page_end)
  {
  	flush_cache_vmap(

  		pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
  		pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));

  }
  
  /**
   * pcpu_populate_chunk - populate and map an area of a pcpu_chunk
   * @chunk: chunk of interest

   * @page_start: the start page
   * @page_end: the end page

   *
   * For each cpu, populate and map pages [@page_start,@page_end) into

   * @chunk.

   *
   * CONTEXT:
   * pcpu_alloc_mutex, does GFP_KERNEL allocation.
   */

  static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
  			       int page_start, int page_end)

  {

  	struct page **pages;

  	pages = pcpu_get_pages(chunk);

  	if (!pages)
  		return -ENOMEM;

  	if (pcpu_alloc_pages(chunk, pages, page_start, page_end))
  		return -ENOMEM;

  	if (pcpu_map_pages(chunk, pages, page_start, page_end)) {
  		pcpu_free_pages(chunk, pages, page_start, page_end);
  		return -ENOMEM;

  	}
  	pcpu_post_map_flush(chunk, page_start, page_end);

  	return 0;

  }
  
  /**
   * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
   * @chunk: chunk to depopulate

   * @page_start: the start page
   * @page_end: the end page

   *
   * For each cpu, depopulate and unmap pages [@page_start,@page_end)

   * from @chunk.

   *
   * CONTEXT:
   * pcpu_alloc_mutex.
   */

  static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
  				  int page_start, int page_end)

  {

  	struct page **pages;

  	/*
  	 * If control reaches here, there must have been at least one
  	 * successful population attempt so the temp pages array must
  	 * be available now.
  	 */

  	pages = pcpu_get_pages(chunk);

  	BUG_ON(!pages);
  
  	/* unmap and free */
  	pcpu_pre_unmap_flush(chunk, page_start, page_end);

  	pcpu_unmap_pages(chunk, pages, page_start, page_end);

  
  	/* no need to flush tlb, vmalloc will handle it lazily */

  	pcpu_free_pages(chunk, pages, page_start, page_end);

  }
  
  static struct pcpu_chunk *pcpu_create_chunk(void)
  {
  	struct pcpu_chunk *chunk;
  	struct vm_struct **vms;
  
  	chunk = pcpu_alloc_chunk();
  	if (!chunk)
  		return NULL;
  
  	vms = pcpu_get_vm_areas(pcpu_group_offsets, pcpu_group_sizes,

  				pcpu_nr_groups, pcpu_atom_size);

  	if (!vms) {
  		pcpu_free_chunk(chunk);
  		return NULL;
  	}
  
  	chunk->data = vms;
  	chunk->base_addr = vms[0]->addr - pcpu_group_offsets[0];
  	return chunk;
  }
  
  static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
  {
  	if (chunk && chunk->data)
  		pcpu_free_vm_areas(chunk->data, pcpu_nr_groups);
  	pcpu_free_chunk(chunk);
  }
  
  static struct page *pcpu_addr_to_page(void *addr)
  {
  	return vmalloc_to_page(addr);
  }
  
  static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
  {
  	/* no extra restriction */
  	return 0;
  }