Messages in this thread |  | | Date | Wed, 6 Feb 2013 12:51:03 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: don't overwrite mm->def_flags in do_mlockall() |
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On Wed, 6 Feb 2013 16:49:34 +0100 Gerald Schaefer <gerald.schaefer@de.ibm.com> wrote:
> With commit 8e72033 "thp: make MADV_HUGEPAGE check for mm->def_flags" > the VM_NOHUGEPAGE flag may be set on s390 in mm->def_flags for certain > processes, to prevent future thp mappings. This would be overwritten > by do_mlockall(), which sets it back to 0 with an optional VM_LOCKED > flag set. > > To fix this, instead of overwriting mm->def_flags in do_mlockall(), > only the VM_LOCKED flag should be set or cleared.
What are the user-visible effects here? Looking at the 274023da1e8 changelog, I'm guessing that it might be pretty nasty - kvm breakage?
> --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -517,11 +517,11 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len) > static int do_mlockall(int flags) > { > struct vm_area_struct * vma, * prev = NULL; > - unsigned int def_flags = 0; > > if (flags & MCL_FUTURE) > - def_flags = VM_LOCKED; > - current->mm->def_flags = def_flags; > + current->mm->def_flags |= VM_LOCKED; > + else > + current->mm->def_flags &= ~VM_LOCKED; > if (flags == MCL_FUTURE) > goto out;
Michal sent an equivalent patch last month: http://ozlabs.org/~akpm/mmotm/broken-out/mm-make-mlockall-preserve-flags-other-than-vm_locked-in-def_flags.patch.
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