linux-kernel - [RFC v10 PATCH 2/3] mm: unmap VM_HUGETLB mappings with optimized path

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Message-Id: <1536957299-43536-3-git-send-email-yang.shi@linux.alibaba.com>
Date:   Sat, 15 Sep 2018 04:34:58 +0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     mhocko@...nel.org, willy@...radead.org, ldufour@...ux.vnet.ibm.com,
        vbabka@...e.cz, kirill@...temov.name, akpm@...ux-foundation.org
Cc:     dave.hansen@...el.com, oleg@...hat.com, srikar@...ux.vnet.ibm.com,
        yang.shi@...ux.alibaba.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [RFC v10 PATCH 2/3] 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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 2879b19..991e066 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2777,7 +2777,7 @@ static int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 			 * update vm_flags.
 			 */
 			if (downgrade &&
-			    (tmp->vm_flags & (VM_HUGETLB | VM_PFNMAP)))
+			    (tmp->vm_flags & VM_PFNMAP))
 				downgrade = false;
 
 			tmp = tmp->vm_next;
-- 
1.8.3.1