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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> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 4A3C714001F X-Stat-Signature: uudemd8turo39h9r8hwfzackd3efdw13 X-HE-Tag: 1692211914-60816 X-HE-Meta: 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 KdaPe31w 6SRl0bU9cGjOcI1TWg62hDds9drXW6KnMaHlTXKTxLbEPJy8hjcc3SYigzl6+HAlEkMHVMLBv0x0Yu9QQDiDVXlehr6S+OzxzlyyQQJk6mABDD/PDx6ISZjLXgOf+7j2RivpGY7hyQ2LujMrwnyoU0cQD2SR1QpHNGQbdLR4GXmSMLU7T0+Dn35ZE4csP3sfTh1jy47NqVkHTefxVN+R9uJrTlKdIzlrwmZnEWYOpkwbP8Sn/rUjq8rioQj6zYpOqOja+uuDq6H7KgVCH9jVERqQbPhQ3a3PHKsuG0rltXtCrUUeCf0UPB0CK6tKSAs0tTTE4WKq4v6NuAjhLt7qE6J/G3QNAQkFi/HRvgiIp652r7phkDyAofq9tP/cPTpbqTkd9 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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