linux-kernel - [RFC v8 PATCH 4/5] mm: unmap VM_HUGETLB mappings with optimized path

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Message-Id: <1534358990-85530-5-git-send-email-yang.shi@linux.alibaba.com>
Date:   Thu, 16 Aug 2018 02:49:49 +0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     mhocko@...nel.org, willy@...radead.org, ldufour@...ux.vnet.ibm.com,
        kirill@...temov.name, vbabka@...e.cz, akpm@...ux-foundation.org,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org
Cc:     yang.shi@...ux.alibaba.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [RFC v8 PATCH 4/5] mm: unmap VM_HUGETLB mappings with optimized path

When unmapping VM_HUGETLB mappings, vm flags need to be updated. Since
the vmas have been detached, so it sounds safe to update vm flags with
read mmap_sem.

Cc: Michal Hocko <mhocko@...nel.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
---
 mm/mmap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index e92f680..3b9f734 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2812,7 +2812,6 @@ static int do_munmap_zap_rlock(struct mm_struct *mm, unsigned long start,
 
 	/*
 	 * Unmapping vmas, which have:
-	 *   VM_HUGETLB or
 	 *   VM_PFNMAP or
 	 *   uprobes
 	 * need get done with write mmap_sem held since they may update
@@ -2821,7 +2820,7 @@ static int do_munmap_zap_rlock(struct mm_struct *mm, unsigned long start,
 	for (vma = start_vma; vma && vma->vm_start < end; vma = vma->vm_next) {
 		if ((vma->vm_file &&
 		    has_uprobes(vma, vma->vm_start, vma->vm_end)) ||
-		    (vma->vm_flags & (VM_HUGETLB | VM_PFNMAP)))
+		    (vma->vm_flags & VM_PFNMAP))
 			goto regular_path;
 	}
 
-- 
1.8.3.1