Messages in this thread | | | Date | Fri, 5 Aug 2022 11:23:26 -0700 | From | Mike Kravetz <> | Subject | Re: [PATCH v1 1/2] mm/hugetlb: fix hugetlb not supporting write-notify |
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On 08/05/22 14:14, Peter Xu wrote: > On Fri, Aug 05, 2022 at 01:03:28PM +0200, David Hildenbrand wrote: > > diff --git a/mm/mmap.c b/mm/mmap.c > > index 61e6135c54ef..462a6b0344ac 100644 > > --- a/mm/mmap.c > > +++ b/mm/mmap.c > > @@ -1683,6 +1683,13 @@ int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot) > > if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED))) > > return 0; > > > > + /* > > + * Hugetlb does not require/support writenotify; especially, it does not > > + * support softdirty tracking. > > + */ > > + if (is_vm_hugetlb_page(vma)) > > + return 0; > > I'm kind of confused here.. you seems to be fixing up soft-dirty for > hugetlb but here it's explicitly forbidden. > > Could you explain a bit more on why this patch is needed if (assume > there'll be a working) patch 2 being provided? >
No comments on the patch, but ...
Since it required little thought, I ran the test program on next-20220802 and was surprised that the issue did not recreate. Even added a simple printk to make sure we were getting into vma_wants_writenotify with a hugetlb vma. We were.
I can easily recreate with an older Fedora kernel.
Will be trying to understand why this is the case. -- Mike Kravetz
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