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(p200300cbc74b8b005520fa3cc527592f.dip0.t-ipconnect.de. [2003:cb:c74b:8b00:5520:fa3c:c527:592f]) by smtp.gmail.com with ESMTPSA id t18-20020adff612000000b00317b0155502sm22222551wrp.8.2023.08.16.11.51.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Aug 2023 11:51:50 -0700 (PDT) Message-ID: Date: Wed, 16 Aug 2023 20:51:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH RFC v3] mm: Proper document tail pages fields for folio To: Matthew Wilcox Cc: Peter Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Hugh Dickins , "Kirill A . Shutemov" , Randy Dunlap , Mike Kravetz , Yu Zhao , Ryan Roberts , Andrew Morton , Yang Shi References: <20230815212547.431693-1-peterx@redhat.com> Content-Language: en-US From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16.08.23 20:41, Matthew Wilcox wrote: > On Wed, Aug 16, 2023 at 03:33:30PM +0200, David Hildenbrand wrote: >> My simple tests passed so far. If there isn't something obvious missing, >> I can do more testing and send this as an official patch. > > I think you missed one: > > +++ b/mm/swapfile.c > @@ -1490,7 +1490,7 @@ int swp_swapcount(swp_entry_t entry) > > page = vmalloc_to_page(p->swap_map + offset); > offset &= ~PAGE_MASK; > - VM_BUG_ON(page_private(page) != SWP_CONTINUED); > + VM_BUG_ON(page_swap_entry(page).val != SWP_CONTINUED); That falls under the "weird handling of SWP_CONTINUED using vmalloced pages". So different user of page_private(). Note that we don't even store swap entries in there but extended swap counts. > > do { > page = list_next_entry(page, lru); > > I'm not smart enough to understand the use of the one in > add_swap_count_continuation(). Maybe that also needs to be fixed? No, that's independent of THP_SWAP, we're not working on the memmap of the THP but some weird extension of swap counts. Thanks for having a look! -- Cheers, David / dhildenb