Andrew, please apply.
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: David Gibson <[email protected]>
Index: working-2.6/arch/powerpc/mm/hugetlbpage.c
===================================================================
--- working-2.6.orig/arch/powerpc/mm/hugetlbpage.c 2005-11-24 13:38:12.000000000 +1100
+++ working-2.6/arch/powerpc/mm/hugetlbpage.c 2005-11-24 14:09:42.000000000 +1100
@@ -524,6 +524,17 @@ 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;
@@ -584,6 +595,7 @@ unsigned long hugetlb_get_unmapped_area(
{
int lastshift;
u16 areamask, curareas;
+ struct vm_area_struct *vma;
if (HPAGE_SHIFT == 0)
return -EINVAL;
@@ -593,15 +605,28 @@ unsigned long hugetlb_get_unmapped_area(
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) {
@@ -616,12 +641,22 @@ unsigned long hugetlb_get_unmapped_area(
} 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) {
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson