From: Vlastimil Babka <vbabka@suse.cz>
To: David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Shakeel Butt <shakeelb@google.com>,
John Hubbard <jhubbard@nvidia.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Yang Shi <shy828301@gmail.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>,
Jann Horn <jannh@google.com>, Michal Hocko <mhocko@kernel.org>,
Nadav Amit <namit@vmware.com>, Rik van Riel <riel@surriel.com>,
Roman Gushchin <guro@fb.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Peter Xu <peterx@redhat.com>, Donald Dutile <ddutile@redhat.com>,
Christoph Hellwig <hch@lst.de>, Oleg Nesterov <oleg@redhat.com>,
Jan Kara <jack@suse.cz>, Liang Zhang <zhangliang5@huawei.com>,
Pedro Gomes <pedrodemargomes@gmail.com>,
Oded Gabbay <oded.gabbay@gmail.com>,
linux-mm@kvack.org
Subject: Re: [PATCH v3 14/16] mm: support GUP-triggered unsharing of anonymous pages
Date: Tue, 19 Apr 2022 18:31:49 +0200 [thread overview]
Message-ID: <3cc33611-a430-1ce4-bb30-7dc62a530cb8@suse.cz> (raw)
In-Reply-To: <c003964a-9fa1-b17c-158a-8ccbf4ff8656@redhat.com>
On 4/19/22 18:29, David Hildenbrand wrote:
>>> @@ -4515,8 +4550,11 @@ static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)
>>> /* `inline' is required to avoid gcc 4.1.2 build error */
>>> static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
>>> {
>>> + const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
>>> +
>>> if (vma_is_anonymous(vmf->vma)) {
>>> - if (userfaultfd_huge_pmd_wp(vmf->vma, vmf->orig_pmd))
>>> + if (unlikely(unshare) &&
>>
>> Is this condition flipped, should it be "likely(!unshare)"? As the similar
>> code in do_wp_page() does.
>
> Good catch, this should affect uffd-wp on THP -- it wouldn't trigger as expected. Thanks a lot for finding that!
Yay, glad I was right this time.
>>
>>> + userfaultfd_huge_pmd_wp(vmf->vma, vmf->orig_pmd))
>>> return handle_userfault(vmf, VM_UFFD_WP);
>>> return do_huge_pmd_wp_page(vmf);
>>> }
>>> @@ -4651,10 +4689,11 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
>>> update_mmu_tlb(vmf->vma, vmf->address, vmf->pte);
>>> goto unlock;
>>> }
>>> - if (vmf->flags & FAULT_FLAG_WRITE) {
>>> + if (vmf->flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) {
>>> if (!pte_write(entry))
>>> return do_wp_page(vmf);
>>> - entry = pte_mkdirty(entry);
>>> + else if (likely(vmf->flags & FAULT_FLAG_WRITE))
>>> + entry = pte_mkdirty(entry);
>>> }
>>> entry = pte_mkyoung(entry);
>>> if (ptep_set_access_flags(vmf->vma, vmf->address, vmf->pte, entry,
>>
>
>
> So the following on top, right?
Looks good!
> diff --git a/mm/memory.c b/mm/memory.c
> index 8b3cb73f5e44..4584c7e87a70 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3137,7 +3137,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
> free_swap_cache(old_page);
> put_page(old_page);
> }
> - return page_copied && !unshare ? VM_FAULT_WRITE : 0;
> + return (page_copied && !unshare) ? VM_FAULT_WRITE : 0;
> oom_free_new:
> put_page(new_page);
> oom:
> @@ -4604,7 +4604,7 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
> const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
>
> if (vma_is_anonymous(vmf->vma)) {
> - if (unlikely(unshare) &&
> + if (likely(!unshare) &&
> userfaultfd_huge_pmd_wp(vmf->vma, vmf->orig_pmd))
> return handle_userfault(vmf, VM_UFFD_WP);
> return do_huge_pmd_wp_page(vmf);
>
>
next prev parent reply other threads:[~2022-04-19 16:31 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-29 16:04 [PATCH v3 00/16] mm: COW fixes part 2: reliable GUP pins of anonymous pages David Hildenbrand
2022-03-29 16:04 ` [PATCH v3 01/16] mm/rmap: fix missing swap_free() in try_to_unmap() after arch_unmap_one() failed David Hildenbrand
2022-04-11 16:04 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 02/16] mm/hugetlb: take src_mm->write_protect_seq in copy_hugetlb_page_range() David Hildenbrand
2022-04-11 16:15 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 03/16] mm/memory: slightly simplify copy_present_pte() David Hildenbrand
2022-04-11 16:38 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 04/16] mm/rmap: split page_dup_rmap() into page_dup_file_rmap() and page_try_dup_anon_rmap() David Hildenbrand
2022-04-11 18:18 ` Vlastimil Babka
2022-04-12 8:06 ` David Hildenbrand
2022-03-29 16:04 ` [PATCH v3 05/16] mm/rmap: convert RMAP flags to a proper distinct rmap_t type David Hildenbrand
2022-04-12 8:11 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 06/16] mm/rmap: remove do_page_add_anon_rmap() David Hildenbrand
2022-04-12 8:13 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 07/16] mm/rmap: pass rmap flags to hugepage_add_anon_rmap() David Hildenbrand
2022-04-12 8:37 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 08/16] mm/rmap: drop "compound" parameter from page_add_new_anon_rmap() David Hildenbrand
2022-04-12 8:47 ` Vlastimil Babka
2022-04-12 9:37 ` David Hildenbrand
2022-04-13 12:26 ` Matthew Wilcox
2022-04-13 12:28 ` David Hildenbrand
2022-04-13 12:48 ` Matthew Wilcox
2022-04-13 16:20 ` David Hildenbrand
2022-03-29 16:04 ` [PATCH v3 09/16] mm/rmap: use page_move_anon_rmap() when reusing a mapped PageAnon() page exclusively David Hildenbrand
2022-04-12 9:26 ` Vlastimil Babka
2022-04-12 9:28 ` David Hildenbrand
2022-03-29 16:04 ` [PATCH v3 10/16] mm/huge_memory: remove outdated VM_WARN_ON_ONCE_PAGE from unmap_page() David Hildenbrand
2022-04-12 9:37 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 11/16] mm/page-flags: reuse PG_mappedtodisk as PG_anon_exclusive for PageAnon() pages David Hildenbrand
2022-04-13 8:25 ` Vlastimil Babka
2022-04-13 10:28 ` David Hildenbrand
2022-04-13 14:55 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 12/16] mm: remember exclusively mapped anonymous pages with PG_anon_exclusive David Hildenbrand
2022-04-13 16:28 ` Vlastimil Babka
2022-04-13 16:39 ` David Hildenbrand
2022-04-13 18:28 ` Vlastimil Babka
2022-04-19 16:46 ` David Hildenbrand
2022-04-13 18:29 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 13/16] mm/gup: disallow follow_page(FOLL_PIN) David Hildenbrand
2022-04-14 15:18 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 14/16] mm: support GUP-triggered unsharing of anonymous pages David Hildenbrand
2022-04-14 17:15 ` Vlastimil Babka
2022-04-19 16:29 ` David Hildenbrand
2022-04-19 16:31 ` Vlastimil Babka [this message]
2022-03-29 16:04 ` [PATCH v3 15/16] mm/gup: trigger FAULT_FLAG_UNSHARE when R/O-pinning a possibly shared anonymous page David Hildenbrand
2022-04-19 15:56 ` Vlastimil Babka
2022-03-29 16:04 ` [PATCH v3 16/16] mm/gup: sanity-check with CONFIG_DEBUG_VM that anonymous pages are exclusive when (un)pinning David Hildenbrand
2022-04-19 17:40 ` Vlastimil Babka
2022-04-21 9:15 ` David Hildenbrand
2022-04-22 6:54 ` Vlastimil Babka
2022-03-29 16:09 ` [PATCH v3 00/16] mm: COW fixes part 2: reliable GUP pins of anonymous pages David Hildenbrand
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