arch/x86/mm/hugetlbpage.c - kernel/msm-4.9 - Gitiles

 /*
  * IA-32 Huge TLB Page Support for Kernel.
  *
  * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
  */

 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
 #include <linux/pagemap.h>
 #include <linux/err.h>
 #include <linux/sysctl.h>
 #include <asm/mman.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/pgalloc.h>

 static unsigned long page_table_shareable(struct vm_area_struct *svma,
 				struct vm_area_struct *vma,
 				unsigned long addr, pgoff_t idx)
 {
 	unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
 				svma->vm_start;
 	unsigned long sbase = saddr & PUD_MASK;
 	unsigned long s_end = sbase + PUD_SIZE;

 	/* Allow segments to share if only one is marked locked */
 	unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED;
 	unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED;

 	/*
 	 * match the virtual addresses, permission and the alignment of the
 	 * page table page.
 	 */
 	if (pmd_index(addr) != pmd_index(saddr) ||
 	    vm_flags != svm_flags ||
 	    sbase < svma->vm_start || svma->vm_end < s_end)
 		return 0;

 	return saddr;
 }

 static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
 {
 	unsigned long base = addr & PUD_MASK;
 	unsigned long end = base + PUD_SIZE;

 	/*
 	 * check on proper vm_flags and page table alignment
 	 */
 	if (vma->vm_flags & VM_MAYSHARE &&
 	    vma->vm_start <= base && end <= vma->vm_end)
 		return 1;
 	return 0;
 }

 /*
  * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
  * and returns the corresponding pte. While this is not necessary for the
  * !shared pmd case because we can allocate the pmd later as well, it makes the
  * code much cleaner. pmd allocation is essential for the shared case because
  * pud has to be populated inside the same i_mmap_mutex section - otherwise
  * racing tasks could either miss the sharing (see huge_pte_offset) or select a
  * bad pmd for sharing.
  */
 static pte_t *
 huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
 {
 	struct vm_area_struct *vma = find_vma(mm, addr);
 	struct address_space *mapping = vma->vm_file->f_mapping;
 	pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
 			vma->vm_pgoff;
 	struct vm_area_struct *svma;
 	unsigned long saddr;
 	pte_t *spte = NULL;
 	pte_t *pte;

 	if (!vma_shareable(vma, addr))
 		return (pte_t *)pmd_alloc(mm, pud, addr);

 	mutex_lock(&mapping->i_mmap_mutex);
 	vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
 		if (svma == vma)
 			continue;

 		saddr = page_table_shareable(svma, vma, addr, idx);
 		if (saddr) {
 			spte = huge_pte_offset(svma->vm_mm, saddr);
 			if (spte) {
 				get_page(virt_to_page(spte));
 				break;
 			}
 		}
 	}

 	if (!spte)
 		goto out;

 	spin_lock(&mm->page_table_lock);
 	if (pud_none(*pud))
 		pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
 	else
 		put_page(virt_to_page(spte));
 	spin_unlock(&mm->page_table_lock);
 out:
 	pte = (pte_t *)pmd_alloc(mm, pud, addr);
 	mutex_unlock(&mapping->i_mmap_mutex);
 	return pte;
 }

 /*
  * unmap huge page backed by shared pte.
  *
  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
  * indicated by page_count > 1, unmap is achieved by clearing pud and
  * decrementing the ref count. If count == 1, the pte page is not shared.
  *
  * called with vma->vm_mm->page_table_lock held.
  *
  * returns: 1 successfully unmapped a shared pte page
  *	    0 the underlying pte page is not shared, or it is the last user
  */
 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
 {
 	pgd_t *pgd = pgd_offset(mm, *addr);
 	pud_t *pud = pud_offset(pgd, *addr);

 	BUG_ON(page_count(virt_to_page(ptep)) == 0);
 	if (page_count(virt_to_page(ptep)) == 1)
 		return 0;

 	pud_clear(pud);
 	put_page(virt_to_page(ptep));
 	*addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
 	return 1;
 }

 pte_t *huge_pte_alloc(struct mm_struct *mm,
 			unsigned long addr, unsigned long sz)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pte_t *pte = NULL;

 	pgd = pgd_offset(mm, addr);
 	pud = pud_alloc(mm, pgd, addr);
 	if (pud) {
 		if (sz == PUD_SIZE) {
 			pte = (pte_t *)pud;
 		} else {
 			BUG_ON(sz != PMD_SIZE);
 			if (pud_none(*pud))
 				pte = huge_pmd_share(mm, addr, pud);
 			else
 				pte = (pte_t *)pmd_alloc(mm, pud, addr);
 		}
 	}
 	BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));

 	return pte;
 }

 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd = NULL;

 	pgd = pgd_offset(mm, addr);
 	if (pgd_present(*pgd)) {
 		pud = pud_offset(pgd, addr);
 		if (pud_present(*pud)) {
 			if (pud_large(*pud))
 				return (pte_t *)pud;
 			pmd = pmd_offset(pud, addr);
 		}
 	}
 	return (pte_t *) pmd;
 }

 #if 0	/* This is just for testing */
 struct page *
 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 {
 	unsigned long start = address;
 	int length = 1;
 	int nr;
 	struct page *page;
 	struct vm_area_struct *vma;

 	vma = find_vma(mm, addr);
 	if (!vma || !is_vm_hugetlb_page(vma))
 		return ERR_PTR(-EINVAL);

 	pte = huge_pte_offset(mm, address);

 	/* hugetlb should be locked, and hence, prefaulted */
 	WARN_ON(!pte || pte_none(*pte));

 	page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];

 	WARN_ON(!PageHead(page));

 	return page;
 }

 int pmd_huge(pmd_t pmd)
 {
 	return 0;
 }

 int pud_huge(pud_t pud)
 {
 	return 0;
 }

 struct page *
 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 		pmd_t *pmd, int write)
 {
 	return NULL;
 }

 #else

 struct page *
 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 {
 	return ERR_PTR(-EINVAL);
 }

 int pmd_huge(pmd_t pmd)
 {
 	return !!(pmd_val(pmd) & _PAGE_PSE);
 }

 int pud_huge(pud_t pud)
 {
 	return !!(pud_val(pud) & _PAGE_PSE);
 }

 struct page *
 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 		pmd_t *pmd, int write)
 {
 	struct page *page;

 	page = pte_page(*(pte_t *)pmd);
 	if (page)
 		page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
 	return page;
 }

 struct page *
 follow_huge_pud(struct mm_struct *mm, unsigned long address,
 		pud_t *pud, int write)
 {
 	struct page *page;

 	page = pte_page(*(pte_t *)pud);
 	if (page)
 		page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
 	return page;
 }

 #endif

 /* x86_64 also uses this file */

 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
 		unsigned long addr, unsigned long len,
 		unsigned long pgoff, unsigned long flags)
 {
 	struct hstate *h = hstate_file(file);
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long start_addr;

 	if (len > mm->cached_hole_size) {
 	        start_addr = mm->free_area_cache;
 	} else {
 	        start_addr = TASK_UNMAPPED_BASE;
 	        mm->cached_hole_size = 0;
 	}

 full_search:
 	addr = ALIGN(start_addr, huge_page_size(h));

 	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
 		/* At this point:  (!vma || addr < vma->vm_end). */
 		if (TASK_SIZE - len < addr) {
 			/*
 			 * Start a new search - just in case we missed
 			 * some holes.
 			 */
 			if (start_addr != TASK_UNMAPPED_BASE) {
 				start_addr = TASK_UNMAPPED_BASE;
 				mm->cached_hole_size = 0;
 				goto full_search;
 			}
 			return -ENOMEM;
 		}
 		if (!vma || addr + len <= vma->vm_start) {
 			mm->free_area_cache = addr + len;
 			return addr;
 		}
 		if (addr + mm->cached_hole_size < vma->vm_start)
 		        mm->cached_hole_size = vma->vm_start - addr;
 		addr = ALIGN(vma->vm_end, huge_page_size(h));
 	}
 }

 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 		unsigned long addr0, unsigned long len,
 		unsigned long pgoff, unsigned long flags)
 {
 	struct hstate *h = hstate_file(file);
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long base = mm->mmap_base;
 	unsigned long addr = addr0;
 	unsigned long largest_hole = mm->cached_hole_size;
 	unsigned long start_addr;

 	/* don't allow allocations above current base */
 	if (mm->free_area_cache > base)
 		mm->free_area_cache = base;

 	if (len <= largest_hole) {
 	        largest_hole = 0;
 		mm->free_area_cache  = base;
 	}
 try_again:
 	start_addr = mm->free_area_cache;

 	/* make sure it can fit in the remaining address space */
 	if (mm->free_area_cache < len)
 		goto fail;

 	/* either no address requested or can't fit in requested address hole */
 	addr = (mm->free_area_cache - len) & huge_page_mask(h);
 	do {
 		/*
 		 * Lookup failure means no vma is above this address,
 		 * i.e. return with success:
 		 */
 		vma = find_vma(mm, addr);
 		if (!vma)
 			return addr;

 		if (addr + len <= vma->vm_start) {
 			/* remember the address as a hint for next time */
 		        mm->cached_hole_size = largest_hole;
 		        return (mm->free_area_cache = addr);
 		} else if (mm->free_area_cache == vma->vm_end) {
 			/* pull free_area_cache down to the first hole */
 			mm->free_area_cache = vma->vm_start;
 			mm->cached_hole_size = largest_hole;
 		}

 		/* remember the largest hole we saw so far */
 		if (addr + largest_hole < vma->vm_start)
 		        largest_hole = vma->vm_start - addr;

 		/* try just below the current vma->vm_start */
 		addr = (vma->vm_start - len) & huge_page_mask(h);
 	} while (len <= vma->vm_start);

 fail:
 	/*
 	 * if hint left us with no space for the requested
 	 * mapping then try again:
 	 */
 	if (start_addr != base) {
 		mm->free_area_cache = base;
 		largest_hole = 0;
 		goto try_again;
 	}
 	/*
 	 * A failed mmap() very likely causes application failure,
 	 * so fall back to the bottom-up function here. This scenario
 	 * can happen with large stack limits and large mmap()
 	 * allocations.
 	 */
 	mm->free_area_cache = TASK_UNMAPPED_BASE;
 	mm->cached_hole_size = ~0UL;
 	addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
 			len, pgoff, flags);

 	/*
 	 * Restore the topdown base:
 	 */
 	mm->free_area_cache = base;
 	mm->cached_hole_size = ~0UL;

 	return addr;
 }

 unsigned long
 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 		unsigned long len, unsigned long pgoff, unsigned long flags)
 {
 	struct hstate *h = hstate_file(file);
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;

 	if (len & ~huge_page_mask(h))
 		return -EINVAL;
 	if (len > TASK_SIZE)
 		return -ENOMEM;

 	if (flags & MAP_FIXED) {
 		if (prepare_hugepage_range(file, addr, len))
 			return -EINVAL;
 		return addr;
 	}

 	if (addr) {
 		addr = ALIGN(addr, huge_page_size(h));
 		vma = find_vma(mm, addr);
 		if (TASK_SIZE - len >= addr &&
 		    (!vma || addr + len <= vma->vm_start))
 			return addr;
 	}
 	if (mm->get_unmapped_area == arch_get_unmapped_area)
 		return hugetlb_get_unmapped_area_bottomup(file, addr, len,
 				pgoff, flags);
 	else
 		return hugetlb_get_unmapped_area_topdown(file, addr, len,
 				pgoff, flags);
 }

 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/

 #ifdef CONFIG_X86_64
 static __init int setup_hugepagesz(char *opt)
 {
 	unsigned long ps = memparse(opt, &opt);
 	if (ps == PMD_SIZE) {
 		hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
 	} else if (ps == PUD_SIZE && cpu_has_gbpages) {
 		hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
 	} else {
 		printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
 			ps >> 20);
 		return 0;
 	}
 	return 1;
 }
 __setup("hugepagesz=", setup_hugepagesz);
 #endif
	/*
	* IA-32 Huge TLB Page Support for Kernel.
	*
	* Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
	*/

	#include <linux/init.h>
	#include <linux/fs.h>
	#include <linux/mm.h>
	#include <linux/hugetlb.h>
	#include <linux/pagemap.h>
	#include <linux/err.h>
	#include <linux/sysctl.h>
	#include <asm/mman.h>
	#include <asm/tlb.h>
	#include <asm/tlbflush.h>
	#include <asm/pgalloc.h>

	static unsigned long page_table_shareable(struct vm_area_struct *svma,
	struct vm_area_struct *vma,
	unsigned long addr, pgoff_t idx)
	{
	unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
	svma->vm_start;
	unsigned long sbase = saddr & PUD_MASK;
	unsigned long s_end = sbase + PUD_SIZE;

	/* Allow segments to share if only one is marked locked */
	unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED;
	unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED;

	/*
	* match the virtual addresses, permission and the alignment of the
	* page table page.
	*/
	if (pmd_index(addr) != pmd_index(saddr) \|\|
	vm_flags != svm_flags \|\|
	sbase < svma->vm_start \|\| svma->vm_end < s_end)
	return 0;

	return saddr;
	}

	static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
	{
	unsigned long base = addr & PUD_MASK;
	unsigned long end = base + PUD_SIZE;

	/*
	* check on proper vm_flags and page table alignment
	*/
	if (vma->vm_flags & VM_MAYSHARE &&
	vma->vm_start <= base && end <= vma->vm_end)
	return 1;
	return 0;
	}

	/*
	* Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
	* and returns the corresponding pte. While this is not necessary for the
	* !shared pmd case because we can allocate the pmd later as well, it makes the
	* code much cleaner. pmd allocation is essential for the shared case because
	* pud has to be populated inside the same i_mmap_mutex section - otherwise
	* racing tasks could either miss the sharing (see huge_pte_offset) or select a
	* bad pmd for sharing.
	*/
	static pte_t *
	huge_pmd_share(struct mm_struct mm, unsigned long addr, pud_t pud)
	{
	struct vm_area_struct *vma = find_vma(mm, addr);
	struct address_space *mapping = vma->vm_file->f_mapping;
	pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
	vma->vm_pgoff;
	struct vm_area_struct *svma;
	unsigned long saddr;
	pte_t *spte = NULL;
	pte_t *pte;

	if (!vma_shareable(vma, addr))
	return (pte_t *)pmd_alloc(mm, pud, addr);

	mutex_lock(&mapping->i_mmap_mutex);
	vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
	if (svma == vma)
	continue;

	saddr = page_table_shareable(svma, vma, addr, idx);
	if (saddr) {
	spte = huge_pte_offset(svma->vm_mm, saddr);
	if (spte) {
	get_page(virt_to_page(spte));
	break;
	}
	}
	}

	if (!spte)
	goto out;

	spin_lock(&mm->page_table_lock);
	if (pud_none(*pud))
	pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
	else
	put_page(virt_to_page(spte));
	spin_unlock(&mm->page_table_lock);
	out:
	pte = (pte_t *)pmd_alloc(mm, pud, addr);
	mutex_unlock(&mapping->i_mmap_mutex);
	return pte;
	}

	/*
	* unmap huge page backed by shared pte.
	*
	* Hugetlb pte page is ref counted at the time of mapping. If pte is shared
	* indicated by page_count > 1, unmap is achieved by clearing pud and
	* decrementing the ref count. If count == 1, the pte page is not shared.
	*
	* called with vma->vm_mm->page_table_lock held.
	*
	* returns: 1 successfully unmapped a shared pte page
	* 0 the underlying pte page is not shared, or it is the last user
	*/
	int huge_pmd_unshare(struct mm_struct mm, unsigned long addr, pte_t *ptep)
	{
	pgd_t pgd = pgd_offset(mm, addr);
	pud_t pud = pud_offset(pgd, addr);

	BUG_ON(page_count(virt_to_page(ptep)) == 0);
	if (page_count(virt_to_page(ptep)) == 1)
	return 0;

	pud_clear(pud);
	put_page(virt_to_page(ptep));
	addr = ALIGN(addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
	return 1;
	}

	pte_t huge_pte_alloc(struct mm_struct mm,
	unsigned long addr, unsigned long sz)
	{
	pgd_t *pgd;
	pud_t *pud;
	pte_t *pte = NULL;

	pgd = pgd_offset(mm, addr);
	pud = pud_alloc(mm, pgd, addr);
	if (pud) {
	if (sz == PUD_SIZE) {
	pte = (pte_t *)pud;
	} else {
	BUG_ON(sz != PMD_SIZE);
	if (pud_none(*pud))
	pte = huge_pmd_share(mm, addr, pud);
	else
	pte = (pte_t *)pmd_alloc(mm, pud, addr);
	}
	}
	BUG_ON(pte && !pte_none(pte) && !pte_huge(pte));

	return pte;
	}

	pte_t huge_pte_offset(struct mm_struct mm, unsigned long addr)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd = NULL;

	pgd = pgd_offset(mm, addr);
	if (pgd_present(*pgd)) {
	pud = pud_offset(pgd, addr);
	if (pud_present(*pud)) {
	if (pud_large(*pud))
	return (pte_t *)pud;
	pmd = pmd_offset(pud, addr);
	}
	}
	return (pte_t *) pmd;
	}

	#if 0 /* This is just for testing */
	struct page *
	follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
	{
	unsigned long start = address;
	int length = 1;
	int nr;
	struct page *page;
	struct vm_area_struct *vma;

	vma = find_vma(mm, addr);
	if (!vma \|\| !is_vm_hugetlb_page(vma))
	return ERR_PTR(-EINVAL);

	pte = huge_pte_offset(mm, address);

	/* hugetlb should be locked, and hence, prefaulted */
	WARN_ON(!pte \|\| pte_none(*pte));

	page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];

	WARN_ON(!PageHead(page));

	return page;
	}

	int pmd_huge(pmd_t pmd)
	{
	return 0;
	}

	int pud_huge(pud_t pud)
	{
	return 0;
	}

	struct page *
	follow_huge_pmd(struct mm_struct *mm, unsigned long address,
	pmd_t *pmd, int write)
	{
	return NULL;
	}

	#else

	struct page *
	follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
	{
	return ERR_PTR(-EINVAL);
	}

	int pmd_huge(pmd_t pmd)
	{
	return !!(pmd_val(pmd) & _PAGE_PSE);
	}

	int pud_huge(pud_t pud)
	{
	return !!(pud_val(pud) & _PAGE_PSE);
	}

	struct page *
	follow_huge_pmd(struct mm_struct *mm, unsigned long address,
	pmd_t *pmd, int write)
	{
	struct page *page;

	page = pte_page((pte_t )pmd);
	if (page)
	page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
	return page;
	}

	struct page *
	follow_huge_pud(struct mm_struct *mm, unsigned long address,
	pud_t *pud, int write)
	{
	struct page *page;

	page = pte_page((pte_t )pud);
	if (page)
	page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
	return page;
	}

	#endif

	/* x86_64 also uses this file */

	#ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
	static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
	unsigned long addr, unsigned long len,
	unsigned long pgoff, unsigned long flags)
	{
	struct hstate *h = hstate_file(file);
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long start_addr;

	if (len > mm->cached_hole_size) {
	start_addr = mm->free_area_cache;
	} else {
	start_addr = TASK_UNMAPPED_BASE;
	mm->cached_hole_size = 0;
	}

	full_search:
	addr = ALIGN(start_addr, huge_page_size(h));

	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
	/* At this point: (!vma \|\| addr < vma->vm_end). */
	if (TASK_SIZE - len < addr) {
	/*
	* Start a new search - just in case we missed
	* some holes.
	*/
	if (start_addr != TASK_UNMAPPED_BASE) {
	start_addr = TASK_UNMAPPED_BASE;
	mm->cached_hole_size = 0;
	goto full_search;
	}
	return -ENOMEM;
	}
	if (!vma \|\| addr + len <= vma->vm_start) {
	mm->free_area_cache = addr + len;
	return addr;
	}
	if (addr + mm->cached_hole_size < vma->vm_start)
	mm->cached_hole_size = vma->vm_start - addr;
	addr = ALIGN(vma->vm_end, huge_page_size(h));
	}
	}

	static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
	unsigned long addr0, unsigned long len,
	unsigned long pgoff, unsigned long flags)
	{
	struct hstate *h = hstate_file(file);
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long base = mm->mmap_base;
	unsigned long addr = addr0;
	unsigned long largest_hole = mm->cached_hole_size;
	unsigned long start_addr;

	/* don't allow allocations above current base */
	if (mm->free_area_cache > base)
	mm->free_area_cache = base;

	if (len <= largest_hole) {
	largest_hole = 0;
	mm->free_area_cache = base;
	}
	try_again:
	start_addr = mm->free_area_cache;

	/* make sure it can fit in the remaining address space */
	if (mm->free_area_cache < len)
	goto fail;

	/* either no address requested or can't fit in requested address hole */
	addr = (mm->free_area_cache - len) & huge_page_mask(h);
	do {
	/*
	* Lookup failure means no vma is above this address,
	* i.e. return with success:
	*/
	vma = find_vma(mm, addr);
	if (!vma)
	return addr;

	if (addr + len <= vma->vm_start) {
	/* remember the address as a hint for next time */
	mm->cached_hole_size = largest_hole;
	return (mm->free_area_cache = addr);
	} else if (mm->free_area_cache == vma->vm_end) {
	/* pull free_area_cache down to the first hole */
	mm->free_area_cache = vma->vm_start;
	mm->cached_hole_size = largest_hole;
	}

	/* remember the largest hole we saw so far */
	if (addr + largest_hole < vma->vm_start)
	largest_hole = vma->vm_start - addr;

	/* try just below the current vma->vm_start */
	addr = (vma->vm_start - len) & huge_page_mask(h);
	} while (len <= vma->vm_start);

	fail:
	/*
	* if hint left us with no space for the requested
	* mapping then try again:
	*/
	if (start_addr != base) {
	mm->free_area_cache = base;
	largest_hole = 0;
	goto try_again;
	}
	/*
	* A failed mmap() very likely causes application failure,
	* so fall back to the bottom-up function here. This scenario
	* can happen with large stack limits and large mmap()
	* allocations.
	*/
	mm->free_area_cache = TASK_UNMAPPED_BASE;
	mm->cached_hole_size = ~0UL;
	addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
	len, pgoff, flags);

	/*
	* Restore the topdown base:
	*/
	mm->free_area_cache = base;
	mm->cached_hole_size = ~0UL;

	return addr;
	}

	unsigned long
	hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
	unsigned long len, unsigned long pgoff, unsigned long flags)
	{
	struct hstate *h = hstate_file(file);
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;

	if (len & ~huge_page_mask(h))
	return -EINVAL;
	if (len > TASK_SIZE)
	return -ENOMEM;

	if (flags & MAP_FIXED) {
	if (prepare_hugepage_range(file, addr, len))
	return -EINVAL;
	return addr;
	}

	if (addr) {
	addr = ALIGN(addr, huge_page_size(h));
	vma = find_vma(mm, addr);
	if (TASK_SIZE - len >= addr &&
	(!vma \|\| addr + len <= vma->vm_start))
	return addr;
	}
	if (mm->get_unmapped_area == arch_get_unmapped_area)
	return hugetlb_get_unmapped_area_bottomup(file, addr, len,
	pgoff, flags);
	else
	return hugetlb_get_unmapped_area_topdown(file, addr, len,
	pgoff, flags);
	}

	#endif /HAVE_ARCH_HUGETLB_UNMAPPED_AREA/

	#ifdef CONFIG_X86_64
	static __init int setup_hugepagesz(char *opt)
	{
	unsigned long ps = memparse(opt, &opt);
	if (ps == PMD_SIZE) {
	hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
	} else if (ps == PUD_SIZE && cpu_has_gbpages) {
	hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
	} else {
	printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
	ps >> 20);
	return 0;
	}
	return 1;
	}
	__setup("hugepagesz=", setup_hugepagesz);
	#endif