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

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Message-Id: <20190619050844.5294-5-alex@ghiti.fr>
Date:   Wed, 19 Jun 2019 01:08:40 -0400
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S . Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-mm@...ck.org,
        Alexandre Ghiti <alex@...ti.fr>
Subject: [PATCH 4/8] x86, hugetlbpage: Start fallback of top-down mmap at mm->mmap_base

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@...ti.fr>
---
 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