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[2003:cb:c702:de00:711b:76af:b335:9b70]) by smtp.gmail.com with ESMTPSA id m7-20020adfe0c7000000b002060e7bbe49sm2764840wri.45.2022.04.21.06.13.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Apr 2022 06:13:14 -0700 (PDT) Message-ID: <67fc9368-0876-b931-14c2-ffa4dac35b6d@redhat.com> Date: Thu, 21 Apr 2022 15:13:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.2 Subject: Re: [PATCH v2 2/3] mm/swapfile: Fix lost swap bits in unuse_pte() Content-Language: en-US To: Miaohe Lin , akpm@linux-foundation.org Cc: willy@infradead.org, vbabka@suse.cz, dhowells@redhat.com, neilb@suse.de, apopple@nvidia.com, surenb@google.com, minchan@kernel.org, peterx@redhat.com, sfr@canb.auug.org.au, naoya.horiguchi@nec.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220421125348.62483-1-linmiaohe@huawei.com> <20220421125348.62483-3-linmiaohe@huawei.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20220421125348.62483-3-linmiaohe@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21.04.22 14:53, Miaohe Lin wrote: > This is observed by code review only but not any real report. > > When we turn off swapping we could have lost the bits stored in the swap > ptes. The new rmap-exclusive bit is fine since that turned into a page > flag, but not for soft-dirty and uffd-wp. Add them. > > Suggested-by: Peter Xu > Signed-off-by: Miaohe Lin > --- > mm/swapfile.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 95b63f69f388..332ccfc76142 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1783,7 +1783,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, > { > struct page *swapcache; > spinlock_t *ptl; > - pte_t *pte; > + pte_t *pte, new_pte; > int ret = 1; > > swapcache = page; > @@ -1832,8 +1832,14 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, > page_add_new_anon_rmap(page, vma, addr); > lru_cache_add_inactive_or_unevictable(page, vma); > } > - set_pte_at(vma->vm_mm, addr, pte, > - pte_mkold(mk_pte(page, vma->vm_page_prot))); > + new_pte = pte_mkold(mk_pte(page, vma->vm_page_prot)); > + if (pte_swp_soft_dirty(*pte)) > + new_pte = pte_mksoft_dirty(new_pte); > + if (pte_swp_uffd_wp(*pte)) { > + new_pte = pte_mkuffd_wp(new_pte); > + new_pte = pte_wrprotect(new_pte); The wrprotect shouldn't be necessary, we don't do a pte_mkwrite(). Note that in do_swap_page() we might have done a maybe_mkwrite(pte_mkdirty(pte)), which is why the pte_wrprotect() is required there. -- Thanks, David / dhildenb