mm/percpu-vm.c - kernel/msm - Gitiles

 /*
  * 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_and_bitmap - get temp pages array and bitmap
  * @chunk: chunk of interest
  * @bitmapp: output parameter for bitmap
  * @may_alloc: may allocate the array
  *
  * Returns pointer to array of pointers to struct page and bitmap,
  * both of which can be indexed with pcpu_page_idx().  The returned
  * array is cleared to zero and *@bitmapp is copied from
  * @chunk->populated.  Note that there is only one array and bitmap
  * and access exclusion is the caller's responsibility.
  *
  * CONTEXT:
  * pcpu_alloc_mutex and does GFP_KERNEL allocation if @may_alloc.
  * Otherwise, don't care.
  *
  * RETURNS:
  * Pointer to temp pages array on success, NULL on failure.
  */
 static struct page **pcpu_get_pages_and_bitmap(struct pcpu_chunk *chunk,
 					       unsigned long **bitmapp,
 					       bool may_alloc)
 {
 	static struct page **pages;
 	static unsigned long *bitmap;
 	size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);
 	size_t bitmap_size = BITS_TO_LONGS(pcpu_unit_pages) *
 			     sizeof(unsigned long);

 	if (!pages || !bitmap) {
 		if (may_alloc && !pages)
 			pages = pcpu_mem_zalloc(pages_size);
 		if (may_alloc && !bitmap)
 			bitmap = pcpu_mem_zalloc(bitmap_size);
 		if (!pages || !bitmap)
 			return NULL;
 	}

 	bitmap_copy(bitmap, chunk->populated, pcpu_unit_pages);

 	*bitmapp = bitmap;
 	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()
  * @populated: populated bitmap
  * @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, unsigned long *populated,
 			    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()
  * @populated: populated bitmap
  * @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, unsigned long *populated,
 			    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
  * @populated: populated bitmap
  * @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, unsigned long *populated,
 			     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);
 	}

 	bitmap_clear(populated, 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
  * @populated: populated bitmap
  * @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 corresponding bits in
  * @chunk->populated bitmap and whatever is necessary for reverse
  * lookup (addr -> chunk).
  */
 static int pcpu_map_pages(struct pcpu_chunk *chunk,
 			  struct page **pages, unsigned long *populated,
 			  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;
 	}

 	/* mapping successful, link chunk and mark populated */
 	for (i = page_start; i < page_end; i++) {
 		for_each_possible_cpu(cpu)
 			pcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],
 					    chunk);
 		__set_bit(i, populated);
 	}

 	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
  * @off: offset to the area to populate
  * @size: size of the area to populate in bytes
  *
  * For each cpu, populate and map pages [@page_start,@page_end) into
  * @chunk.  The area is cleared on return.
  *
  * CONTEXT:
  * pcpu_alloc_mutex, does GFP_KERNEL allocation.
  */
 static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
 {
 	int page_start = PFN_DOWN(off);
 	int page_end = PFN_UP(off + size);
 	int free_end = page_start, unmap_end = page_start;
 	struct page **pages;
 	unsigned long *populated;
 	unsigned int cpu;
 	int rs, re, rc;

 	/* quick path, check whether all pages are already there */
 	rs = page_start;
 	pcpu_next_pop(chunk, &rs, &re, page_end);
 	if (rs == page_start && re == page_end)
 		goto clear;

 	/* need to allocate and map pages, this chunk can't be immutable */
 	WARN_ON(chunk->immutable);

 	pages = pcpu_get_pages_and_bitmap(chunk, &populated, true);
 	if (!pages)
 		return -ENOMEM;

 	/* alloc and map */
 	pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
 		rc = pcpu_alloc_pages(chunk, pages, populated, rs, re);
 		if (rc)
 			goto err_free;
 		free_end = re;
 	}

 	pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
 		rc = pcpu_map_pages(chunk, pages, populated, rs, re);
 		if (rc)
 			goto err_unmap;
 		unmap_end = re;
 	}
 	pcpu_post_map_flush(chunk, page_start, page_end);

 	/* commit new bitmap */
 	bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
 clear:
 	for_each_possible_cpu(cpu)
 		memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
 	return 0;

 err_unmap:
 	pcpu_pre_unmap_flush(chunk, page_start, unmap_end);
 	pcpu_for_each_unpop_region(chunk, rs, re, page_start, unmap_end)
 		pcpu_unmap_pages(chunk, pages, populated, rs, re);
 	pcpu_post_unmap_tlb_flush(chunk, page_start, unmap_end);
 err_free:
 	pcpu_for_each_unpop_region(chunk, rs, re, page_start, free_end)
 		pcpu_free_pages(chunk, pages, populated, rs, re);
 	return rc;
 }

 /**
  * pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
  * @chunk: chunk to depopulate
  * @off: offset to the area to depopulate
  * @size: size of the area to depopulate in bytes
  * @flush: whether to flush cache and tlb or not
  *
  * For each cpu, depopulate and unmap pages [@page_start,@page_end)
  * from @chunk.  If @flush is true, vcache is flushed before unmapping
  * and tlb after.
  *
  * CONTEXT:
  * pcpu_alloc_mutex.
  */
 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
 {
 	int page_start = PFN_DOWN(off);
 	int page_end = PFN_UP(off + size);
 	struct page **pages;
 	unsigned long *populated;
 	int rs, re;

 	/* quick path, check whether it's empty already */
 	rs = page_start;
 	pcpu_next_unpop(chunk, &rs, &re, page_end);
 	if (rs == page_start && re == page_end)
 		return;

 	/* immutable chunks can't be depopulated */
 	WARN_ON(chunk->immutable);

 	/*
 	 * 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_and_bitmap(chunk, &populated, false);
 	BUG_ON(!pages);

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

 	pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
 		pcpu_unmap_pages(chunk, pages, populated, rs, re);

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

 	pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
 		pcpu_free_pages(chunk, pages, populated, rs, re);

 	/* commit new bitmap */
 	bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
 }

 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;
 }
	/*
	* 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_and_bitmap - get temp pages array and bitmap
	* @chunk: chunk of interest
	* @bitmapp: output parameter for bitmap
	* @may_alloc: may allocate the array
	*
	* Returns pointer to array of pointers to struct page and bitmap,
	* both of which can be indexed with pcpu_page_idx(). The returned
	* array is cleared to zero and *@bitmapp is copied from
	* @chunk->populated. Note that there is only one array and bitmap
	* and access exclusion is the caller's responsibility.
	*
	* CONTEXT:
	* pcpu_alloc_mutex and does GFP_KERNEL allocation if @may_alloc.
	* Otherwise, don't care.
	*
	* RETURNS:
	* Pointer to temp pages array on success, NULL on failure.
	*/
	static struct page *pcpu_get_pages_and_bitmap(struct pcpu_chunk chunk,
	unsigned long **bitmapp,
	bool may_alloc)
	{
	static struct page **pages;
	static unsigned long *bitmap;
	size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);
	size_t bitmap_size = BITS_TO_LONGS(pcpu_unit_pages) *
	sizeof(unsigned long);

	if (!pages \|\| !bitmap) {
	if (may_alloc && !pages)
	pages = pcpu_mem_zalloc(pages_size);
	if (may_alloc && !bitmap)
	bitmap = pcpu_mem_zalloc(bitmap_size);
	if (!pages \|\| !bitmap)
	return NULL;
	}

	bitmap_copy(bitmap, chunk->populated, pcpu_unit_pages);

	*bitmapp = bitmap;
	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()
	* @populated: populated bitmap
	* @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, unsigned long populated,
	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()
	* @populated: populated bitmap
	* @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, unsigned long populated,
	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
	* @populated: populated bitmap
	* @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, unsigned long populated,
	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);
	}

	bitmap_clear(populated, 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
	* @populated: populated bitmap
	* @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 corresponding bits in
	* @chunk->populated bitmap and whatever is necessary for reverse
	* lookup (addr -> chunk).
	*/
	static int pcpu_map_pages(struct pcpu_chunk *chunk,
	struct page *pages, unsigned long populated,
	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;
	}

	/* mapping successful, link chunk and mark populated */
	for (i = page_start; i < page_end; i++) {
	for_each_possible_cpu(cpu)
	pcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],
	chunk);
	__set_bit(i, populated);
	}

	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
	* @off: offset to the area to populate
	* @size: size of the area to populate in bytes
	*
	* For each cpu, populate and map pages [@page_start,@page_end) into
	* @chunk. The area is cleared on return.
	*
	* CONTEXT:
	* pcpu_alloc_mutex, does GFP_KERNEL allocation.
	*/
	static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
	{
	int page_start = PFN_DOWN(off);
	int page_end = PFN_UP(off + size);
	int free_end = page_start, unmap_end = page_start;
	struct page **pages;
	unsigned long *populated;
	unsigned int cpu;
	int rs, re, rc;

	/* quick path, check whether all pages are already there */
	rs = page_start;
	pcpu_next_pop(chunk, &rs, &re, page_end);
	if (rs == page_start && re == page_end)
	goto clear;

	/* need to allocate and map pages, this chunk can't be immutable */
	WARN_ON(chunk->immutable);

	pages = pcpu_get_pages_and_bitmap(chunk, &populated, true);
	if (!pages)
	return -ENOMEM;

	/* alloc and map */
	pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
	rc = pcpu_alloc_pages(chunk, pages, populated, rs, re);
	if (rc)
	goto err_free;
	free_end = re;
	}

	pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
	rc = pcpu_map_pages(chunk, pages, populated, rs, re);
	if (rc)
	goto err_unmap;
	unmap_end = re;
	}
	pcpu_post_map_flush(chunk, page_start, page_end);

	/* commit new bitmap */
	bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
	clear:
	for_each_possible_cpu(cpu)
	memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
	return 0;

	err_unmap:
	pcpu_pre_unmap_flush(chunk, page_start, unmap_end);
	pcpu_for_each_unpop_region(chunk, rs, re, page_start, unmap_end)
	pcpu_unmap_pages(chunk, pages, populated, rs, re);
	pcpu_post_unmap_tlb_flush(chunk, page_start, unmap_end);
	err_free:
	pcpu_for_each_unpop_region(chunk, rs, re, page_start, free_end)
	pcpu_free_pages(chunk, pages, populated, rs, re);
	return rc;
	}

	/**
	* pcpu_depopulate_chunk - depopulate and unmap an area of a pcpu_chunk
	* @chunk: chunk to depopulate
	* @off: offset to the area to depopulate
	* @size: size of the area to depopulate in bytes
	* @flush: whether to flush cache and tlb or not
	*
	* For each cpu, depopulate and unmap pages [@page_start,@page_end)
	* from @chunk. If @flush is true, vcache is flushed before unmapping
	* and tlb after.
	*
	* CONTEXT:
	* pcpu_alloc_mutex.
	*/
	static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
	{
	int page_start = PFN_DOWN(off);
	int page_end = PFN_UP(off + size);
	struct page **pages;
	unsigned long *populated;
	int rs, re;

	/* quick path, check whether it's empty already */
	rs = page_start;
	pcpu_next_unpop(chunk, &rs, &re, page_end);
	if (rs == page_start && re == page_end)
	return;

	/* immutable chunks can't be depopulated */
	WARN_ON(chunk->immutable);

	/*
	* 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_and_bitmap(chunk, &populated, false);
	BUG_ON(!pages);

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

	pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
	pcpu_unmap_pages(chunk, pages, populated, rs, re);

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

	pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
	pcpu_free_pages(chunk, pages, populated, rs, re);

	/* commit new bitmap */
	bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
	}

	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;
	}