[PATCH 4/8] x86, hugetlbpage: Start fallback of top-down mmap at mm->mmap_base

[Alexandre Ghiti]

In case of mmap failure in top-down mode, there is no need to go through
the whole address space again for the bottom-up fallback: the goal of this
fallback is to find, as a last resort, space between the top-down mmap base
and the stack, which is the only place not covered by the top-down mmap.

Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
---
 arch/x86/mm/hugetlbpage.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index fab095362c50..4b90339aef50 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -106,11 +106,12 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 {
 	struct hstate *h = hstate_file(file);
 	struct vm_unmapped_area_info info;
+	unsigned long mmap_base = get_mmap_base(0);
 
 	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 	info.length = len;
 	info.low_limit = PAGE_SIZE;
-	info.high_limit = get_mmap_base(0);
+	info.high_limit = mmap_base;
 
 	/*
 	 * If hint address is above DEFAULT_MAP_WINDOW, look for unmapped area
@@ -132,7 +133,7 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 	if (addr & ~PAGE_MASK) {
 		VM_BUG_ON(addr != -ENOMEM);
 		info.flags = 0;
-		info.low_limit = TASK_UNMAPPED_BASE;
+		info.low_limit = mmap_base;
 		info.high_limit = TASK_SIZE_LOW;
 		addr = vm_unmapped_area(&info);
 	}
-- 
2.20.1