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Shutemov" , Hugh Dickins , Andrew Morton Subject: Re: [PATCH] mm: Wire up tail page poisoning over ->mappings Message-ID: References: <20230815210659.430010-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230815210659.430010-1-peterx@redhat.com> X-Rspamd-Queue-Id: EF0AE100012 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: qipnwydojnijeycocjhr36qb3eebhgpd X-HE-Tag: 1692396872-896284 X-HE-Meta: U2FsdGVkX19HToiBWUePOd1INlEzFZLmUTyPy/k7nlo7OR4y7Gy6hrPMt3QCRRQd5dIzW09ZaL3KUdDJxB9Kdizrg6yIp03s0rCnLw7cf//SaP8DkoKbyBXDAfI6iLrWAIhMEqowc0osni8vLeESuFYgT6KeXLVax139P2trbW7/bLexRsFZljdvl+ywfEvIjKQ0tkJzHsQVI5IlO4/mi5BwQM79iNsz3Tt/LW9NTbhJ40M4BzjUyjS82y+PE3KHwOk4MINuYk2b8K2l+smL2n4LX9zYUZjSumOGhT3/fr20WeaWFymZ2wWDylzdzaDV1YTS7WYybsEucDGHjtN4thm3RNS6KLzm0tCId1sRh6drzguxD+z0CV6R2ezOGk3H++qt5HhqpOj5JMBJg/NtxA1eFVOs8tR5gFLz+EHR9Yp8NI+KKWMmLok3m25jH/q/ABgNVQdLfz1OivA/qP5V8Zow64+NpBMHb8xYh7cXVzikkv6qxv/J5euJrstpbrTrpGXn38l2/uwoxgiTzPv0XRw1sjhLgbcYNP9hz4DEvCZSgre/6l7CCSL28ydQXSwJmsqxitxfBS6QiNNGf2voJqy81SiRWHwK+Fb4Bs1IcAcANAImqQdEI/KmPMZOvgh2GTvF+atABw+L+LYlkKkpjbZ4Et6dtkR8Lthn3xO4mHbNle5wDW8mr5mTOSr3eD7biZDwukohvO1fgytUPdyw5/8jDLfYevT3muIHM5mDe2MHXzgxeQ3z9r8o4w36XyG4vbsoeTmkJOCECBh/gVVvRJL3zfAOCAyzwWgNTyrEPI13/z/fljUN8r1oPDQ+mre5wgsprgY0hOHHsj8ZzIpaeznfLKblQhtaQHfR/ZaO7TWMsXvmpAEceY8hvoLqzuivHOtA69akgdzMUBgoeAgRTDVQV1/bIjvxPkjlRhzUggXs8Cz82rDSNOx0tLNGoCOGrRfyvEnV6zlDqZBr6Ah a/keJz6g 1QcAHr96O+UDnvMYl24hIbdGt40xnkqgL/A6uYLGY0nAIMbR9rZOzrmaJyT8MFir945yf0OG+DQE01o4f0pn9SGXrE1r+IRipWSLji6wDRXX0+QeKScC9TEaXsfbCPi0s49X3aroB7BVBky/MTfQxwtpwcVDah0zGAFWYpguXubP0IYLzJpQrzHkpy4Sk3UPF97JgWNZY5Pd6gkEp6ImzoWvHwCOpXRfGKayA8Qn+DhUvtTlSlmtfFJfUFCE6/bcN4S/M 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 Tue, Aug 15, 2023 at 05:06:59PM -0400, Peter Xu wrote: > I split this out from another rfc series. Removed RFC tag because it > wasn't for this patch but for the documentation updates. I'll post the rfc > part alone. Comments welcomed, thanks. I still hate it, as I explained here: https://lore.kernel.org/linux-mm/ZNp7yUgUrIpILnXu@casper.infradead.org/ > > + * When the tail page's mapping field reused, it'll be exempted from > > + * ->mapping poisoning and checks. Also see the macro TAIL_MAPPING. > > + */ > > +#define TAIL_MAPPING_REUSED_MAX (2) > > More importantly, I think this is over-parametrisation. If you start to > use extra fields in struct folio, just change the code in page_alloc.c > directly.