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    SubjectRe: [PATCH v2][RFC] add MAP_UNLOCKED mmap flag
    On Thu, Oct 08, 2009 at 11:37:52AM +0200, Johannes Weiner wrote:
    > On Tue, Oct 06, 2009 at 08:53:44PM +0200, Gleb Natapov wrote:
    > > On Tue, Oct 06, 2009 at 08:34:36PM +0200, Johannes Weiner wrote:
    > > > On Tue, Oct 06, 2009 at 07:02:18PM +0200, Gleb Natapov wrote:
    > > > > diff --git a/include/asm-generic/mman.h b/include/asm-generic/mman.h
    > > > > index 32c8bd6..59e0f29 100644
    > > > > --- a/include/asm-generic/mman.h
    > > > > +++ b/include/asm-generic/mman.h
    > > > > @@ -12,6 +12,7 @@
    > > > > #define MAP_NONBLOCK 0x10000 /* do not block on IO */
    > > > > #define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */
    > > > > #define MAP_HUGETLB 0x40000 /* create a huge page mapping */
    > > > > +#define MAP_UNLOCKED 0x80000 /* force page unlocking */
    > > > >
    > > > > #define MCL_CURRENT 1 /* lock all current mappings */
    > > > > #define MCL_FUTURE 2 /* lock all future mappings */
    > > > > diff --git a/mm/mmap.c b/mm/mmap.c
    > > > > index 73f5e4b..7c2abdb 100644
    > > > > --- a/mm/mmap.c
    > > > > +++ b/mm/mmap.c
    > > > > @@ -985,6 +985,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
    > > > > if (!can_do_mlock())
    > > > > return -EPERM;
    > > > >
    > > > > + if (flags & MAP_UNLOKED)
    > > > > + vm_flags &= ~VM_LOCKED;
    > >
    > > > Should we do something special about (MAP_UNLOCKED | MAP_LOCKED)?
    > >
    > > It is simpler to just ignore it. What do you think?
    >
    > I think we should filter it out. It's unlocking even when MAP_LOCKED
    > is set and doing mlock-specific checks also no mlock will happen.
    >
    What do you mean by "filter it out"? Return error. mlock-specific checks
    don't make much sense indeed since locking will not happen.

    --
    Gleb.


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