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    SubjectRe: [PATCH V4 1/6] mm: mlock: Refactor mlock, munlock, and munlockall code
    On Tue, Jul 21, 2015 at 03:59:36PM -0400, Eric B Munson wrote:
    > @@ -648,20 +656,23 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
    > start &= PAGE_MASK;
    >
    > down_write(&current->mm->mmap_sem);
    > - ret = do_mlock(start, len, 0);
    > + ret = apply_vma_flags(start, len, flags, false);
    > up_write(&current->mm->mmap_sem);
    >
    > return ret;
    > }
    >
    > +SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
    > +{
    > + return do_munlock(start, len, VM_LOCKED);
    > +}
    > +
    > static int do_mlockall(int flags)
    > {
    > struct vm_area_struct * vma, * prev = NULL;
    >
    > if (flags & MCL_FUTURE)
    > current->mm->def_flags |= VM_LOCKED;
    > - else
    > - current->mm->def_flags &= ~VM_LOCKED;

    I think this is wrong.

    With current code mlockall(MCL_CURRENT) after mlockall(MCL_FUTURE |
    MCL_CURRENT) would undo future mlocking, without unlocking currently
    mlocked memory.

    The change will break the use-case.

    > if (flags == MCL_FUTURE)
    > goto out;
    >

    --
    Kirill A. Shutemov


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