From: Yang Shi <yang.shi@linux.alibaba.com>
Date: Fri, 26 Oct 2018 22:07:15 +0000 (-0700)
Subject: mm: unmap VM_HUGETLB mappings with optimized path
X-Git-Tag: v5.15~7719^2~57
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b4cefb36051244bcb5651026d862c332a6cac7df;p=platform%2Fkernel%2Flinux-starfive.git

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.

Link: http://lkml.kernel.org/r/1537376621-51150-3-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/mmap.c b/mm/mmap.c
index 330f12c..ea3188b 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;