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Subject[v11 PATCH 3/3] mm: unmap VM_PFNMAP mappings with optimized path
Date
When unmapping VM_PFNMAP 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@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
---
mm/mmap.c | 9 ---------
1 file changed, 9 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 490340e..847a17d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2771,15 +2771,6 @@ static int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
munlock_vma_pages_all(tmp);
}

- /*
- * Unmapping vmas, which have VM_HUGETLB or VM_PFNMAP,
- * need get done with write mmap_sem held since they may
- * update vm_flags.
- */
- if (downgrade &&
- (tmp->vm_flags & VM_PFNMAP))
- downgrade = false;
-
tmp = tmp->vm_next;
}
}
--
1.8.3.1
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