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b=jix3qp/NdvOwD3MXE1iLaiyPurkDmKXMgyvVN5f6craLLKdZ4RrJQ9PJhZcGbVwjj S71p0O32+TVGOhmo1o2Wh2YKmM1YEvC7gHbpUlnNNC+Xont7T1qFz9csoVPDFZhkv6 C5TYeg7PHhn+Ys+rvHXw6L0TOosywYTW7NVJQ1Vk= Date: Mon, 19 Aug 2024 18:46:49 -0700 From: Andrew Morton To: Matthew Wilcox Cc: Suren Baghdasaryan , kent.overstreet@linux.dev, corbet@lwn.net, arnd@arndb.de, mcgrof@kernel.org, rppt@kernel.org, paulmck@kernel.org, thuth@redhat.com, tglx@linutronix.de, bp@alien8.de, xiongwei.song@windriver.com, ardb@kernel.org, david@redhat.com, vbabka@suse.cz, mhocko@suse.com, hannes@cmpxchg.org, roman.gushchin@linux.dev, dave@stgolabs.net, liam.howlett@oracle.com, pasha.tatashin@soleen.com, souravpanda@google.com, keescook@chromium.org, dennis@kernel.org, jhubbard@nvidia.com, yuzhao@google.com, vvvvvv@google.com, rostedt@goodmis.org, iamjoonsoo.kim@lge.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 5/5] alloc_tag: config to store page allocation tag refs in page flags Message-Id: <20240819184649.8fc7da59f89290f716ae0553@linux-foundation.org> In-Reply-To: References: <20240819151512.2363698-1-surenb@google.com> <20240819151512.2363698-6-surenb@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5996010000D X-Stat-Signature: can6td1zaow5xx48kpoyejo16ocuyjm4 X-Rspam-User: X-HE-Tag: 1724118414-322042 X-HE-Meta: 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 y97+juKm uq1vZE+iMM5xjbh1XaqcwvA5QU2lPiAaHteYyGuhEthieU+KreTfjqVmTGnBGB6akyMmzpDjMwWo1O8Xwsi+mxW51DBH+5PfGjIsP7ktCvTUGeD9i1wvngXkvac57RuSwmlE+sP6F6UgULBLo5yu432cF/e89XQSUpAMwX+G1injFm+s75Y8Y/5jC/l5NHWd2gCj2fG2LmPW2k1Y6Tnzz+/u0CWPSZMri7WSFzntyWvXMYIIgaaByA5/MAcV3AOszBj+CGhfvJVhHCARe9NXCPXxnO117iCOfaiuyzemHOtqH1VoLTk5PaKLSY04i5Nxf0vSr7FrS2oV1xI3FNHzfKkPiSw7Pp+c9If5ucM8flNMZDQM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 19 Aug 2024 21:40:34 +0100 Matthew Wilcox wrote: > On Mon, Aug 19, 2024 at 01:39:16PM -0700, Suren Baghdasaryan wrote: > > On Mon, Aug 19, 2024 at 12:34 PM Matthew Wilcox wrote: > > > So if ALLOC_TAG_REF_WIDTH is big enough, it's going to force last_cpupid > > > into struct page. > > > > Thanks for taking a look! > > Yes, but how is this field different from say KASAN_TAG_WIDTH which > > can also force last_cpupid out of page flags? > > Because KASAN isn't for production use? > > > > That will misalign struct page and disable HVO -- with no warning! > > > > mminit_verify_pageflags_layout already has a mminit_dprintk() to > > indicate this condition. Is that not enough? > > Fair. Is a BUILD_BUG_ON() feasible here?