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[2003:cb:c705:1f00:4727:6420:1d4d:ca23]) by smtp.gmail.com with ESMTPSA id j20-20020adfa554000000b002100316b126sm47617wrb.6.2022.06.10.10.39.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Jun 2022 10:39:33 -0700 (PDT) Message-ID: <688dccfb-ec4e-7522-b5ef-18a46337df91@redhat.com> Date: Fri, 10 Jun 2022 19:39:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: Freeing page flags To: Mike Rapoport , Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org References: 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 Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1654882778; a=rsa-sha256; cv=none; b=un3UouH0S3e8mhkHcvzUMvLlQ9aVgsNY3KCoi2LH7vdTFnEyzcivjxHtlwN1BMj4WzekAN xK5yO/bb1a6bzaPcrmN+elN/bPEJ82g4UKJPvaXDk7ZiozDI3W3wvNSx5y9vWBfDuRlACL XINU9lBAJCX+2GnJkpgMaLH8O4dcRZw= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Qw3TKYEf; spf=none (imf13.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1654882778; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=J8z5Zt980Qbu7w4WytKw8QIuAeP80x+ID2G+tu0x/MM=; b=RjGxvwdnNS/bJJNdI6qhEH96/NcffMavp178ecxMlfmcxUWCKJW9xN0I1mTovfYb8KKbnc XhH2N+KwvEtsD16QQMij1GJc+YUZfpB2OGfm/qCE5Qphu1E8+Bvf4a6OFXLJa/nhsmklBo 6/skDRBouSy6IdeQ4N/Bsdyxu8Io3QA= X-Rspamd-Queue-Id: A1BEA20063 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Qw3TKYEf; spf=none (imf13.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: mj51q5rmippiccasgroejf793sdj6gaf X-HE-Tag: 1654882778-224006 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 23.05.22 08:38, Mike Rapoport wrote: > On Thu, May 12, 2022 at 09:54:59PM +0100, Matthew Wilcox wrote: >> The LWN writeup [1] on merging the MGLRU reminded me that I need to send >> out a plan for removing page flags that we can do without. >> >> 4. I think I can also consolidate PG_slab and PG_reserved into a "single >> bit" (not really, but change the encoding so that effectively they only >> take a single bit). > > PG_reserved could be a PageType, AFAIR no reserved pages are ever mapped to > userspace include/linux/page-flags.h documents for PG_reserved: "Pages part of the kernel image (including vDSO)" Further, vm_normal_page() contains a comment "NOTE! We still have PageReserved() pages in the page tables. eg. VDSO mappings can cause them to exist." -- Thanks, David / dhildenb