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[2003:cb:c74b:8b00:5520:fa3c:c527:592f]) by smtp.gmail.com with ESMTPSA id u16-20020a5d4690000000b00313de682eb3sm21547979wrq.65.2023.08.16.08.21.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Aug 2023 08:21:58 -0700 (PDT) Message-ID: <46e3dfa6-9fea-df51-cff7-e1b916e77a31@redhat.com> Date: Wed, 16 Aug 2023 17:21:57 +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 v2 12/13] mm: Add tail private fields to struct folio To: "Matthew Wilcox (Oracle)" , Andrew Morton Cc: Jens Axboe , io-uring@vger.kernel.org, linux-mm@kvack.org References: <20230816151201.3655946-1-willy@infradead.org> <20230816151201.3655946-13-willy@infradead.org> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230816151201.3655946-13-willy@infradead.org> 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: rspam06 X-Rspamd-Queue-Id: 666154002F X-Stat-Signature: s4z1csyygoyrd3uaoosk8jbwb1aere4i X-HE-Tag: 1692199323-350991 X-HE-Meta: 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 RuEa6ix/ 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 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 17:12, Matthew Wilcox (Oracle) wrote: > Because THP_SWAP uses page->private for each page, we must not use > the space which overlaps that field for anything which would conflict > with that. We avoid the conflict on 32-bit systems by disallowing > THP_SWAP on 32-bit. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > include/linux/mm_types.h | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 659c7b84726c..3880b3f2e321 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -340,8 +340,11 @@ struct folio { > atomic_t _pincount; > #ifdef CONFIG_64BIT > unsigned int _folio_nr_pages; > -#endif > + /* 4 byte gap here */ > /* private: the union with struct page is transitional */ > + /* Fix THP_SWAP to not use tail->private */ > + unsigned long _private_1; If you could give https://lkml.kernel.org/r/b887e764-ffa3-55ee-3c44-69cb15f8a115@redhat.com a quick glimpse to see if anything important jumps at you, that would be great. That really should be fixed. -- Cheers, David / dhildenb