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Date: Fri, 5 Aug 2022 20:25:37 +0200 From: David Hildenbrand <david@...hat.com> To: Mike Kravetz <mike.kravetz@...cle.com>, Peter Xu <peterx@...hat.com> Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, Muchun Song <songmuchun@...edance.com>, Peter Feiner <pfeiner@...gle.com>, "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, stable@...r.kernel.org Subject: Re: [PATCH v1 1/2] mm/hugetlb: fix hugetlb not supporting write-notify On 05.08.22 20:23, Mike Kravetz wrote: > 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. ... does your config have CONFIG_MEM_SOFT_DIRTY enabled? -- Thanks, David / dhildenb
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