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mm: unmap VM_PFNMAP mappings with optimized path
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. Link: http://lkml.kernel.org/r/1537376621-51150-4-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>
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@ -2771,15 +2771,6 @@ static int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
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munlock_vma_pages_all(tmp);
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}
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/*
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* Unmapping vmas, which have VM_HUGETLB or VM_PFNMAP,
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* need get done with write mmap_sem held since they may
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* update vm_flags.
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*/
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if (downgrade &&
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(tmp->vm_flags & VM_PFNMAP))
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downgrade = false;
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tmp = tmp->vm_next;
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}
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}
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