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Commit 456752f7 authored by David Gibson's avatar David Gibson Committed by Paul Mackerras
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[PATCH] powerpc: Make hugepage mappings respect hint addresses 



Currently, the powerpc version of hugetlb_get_unmapped_area() entirely
ignores the hint address.  The only way to get a hugepage mapping at a
specified address is with MAP_FIXED, in which case there's no way
(short of parsing /proc/self/maps) for userspace to tell if it will
clobber an existing mapping.  This is inconvenient, so the patch below
makes hugepage mappings use the given hint address if possible.

Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent 706e6b2c

arch/powerpc/mm/hugetlbpage.c

+39 −4
Original line number Diff line number Diff line
@@ -549,6 +549,17 @@ fail: 
	return addr;

}



static int htlb_check_hinted_area(unsigned long addr, unsigned long len)

{

	struct vm_area_struct *vma;



	vma = find_vma(current->mm, addr);

	if (!vma || ((addr + len) <= vma->vm_start))

		return 0;



	return -ENOMEM;

}



static unsigned long htlb_get_low_area(unsigned long len, u16 segmask)

{

	unsigned long addr = 0;
@@ -609,6 +620,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, 
{

	int lastshift;

	u16 areamask, curareas;

	struct vm_area_struct *vma;



	if (HPAGE_SHIFT == 0)

		return -EINVAL;
@@ -618,15 +630,28 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, 
	if (!cpu_has_feature(CPU_FTR_16M_PAGE))

		return -EINVAL;



	/* Paranoia, caller should have dealt with this */

	BUG_ON((addr + len)  < addr);



	if (test_thread_flag(TIF_32BIT)) {

		/* Paranoia, caller should have dealt with this */

		BUG_ON((addr + len) > 0x100000000UL);



		curareas = current->mm->context.low_htlb_areas;



		/* First see if we can do the mapping in the existing

		 * low areas */

		/* First see if we can use the hint address */

		if (addr && (htlb_check_hinted_area(addr, len) == 0)) {

			areamask = LOW_ESID_MASK(addr, len);

			if (open_low_hpage_areas(current->mm, areamask) == 0)

				return addr;

		}



		/* Next see if we can map in the existing low areas */

		addr = htlb_get_low_area(len, curareas);

		if (addr != -ENOMEM)

			return addr;



		/* Finally go looking for areas to open */

		lastshift = 0;

		for (areamask = LOW_ESID_MASK(0x100000000UL-len, len);

		     ! lastshift; areamask >>=1) {
@@ -641,12 +666,22 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, 
	} else {

		curareas = current->mm->context.high_htlb_areas;



		/* First see if we can do the mapping in the existing

		 * high areas */

		/* First see if we can use the hint address */

		/* We discourage 64-bit processes from doing hugepage

		 * mappings below 4GB (must use MAP_FIXED) */

		if ((addr >= 0x100000000UL)

		    && (htlb_check_hinted_area(addr, len) == 0)) {

			areamask = HTLB_AREA_MASK(addr, len);

			if (open_high_hpage_areas(current->mm, areamask) == 0)

				return addr;

		}



		/* Next see if we can map in the existing high areas */

		addr = htlb_get_high_area(len, curareas);

		if (addr != -ENOMEM)

			return addr;



		/* Finally go looking for areas to open */

		lastshift = 0;

		for (areamask = HTLB_AREA_MASK(TASK_SIZE_USER64-len, len);

		     ! lastshift; areamask >>=1) {