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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1sg9B4-000000079lt-26nJ; Mon, 19 Aug 2024 20:40:34 +0000 Date: Mon, 19 Aug 2024 21:40:34 +0100 From: Matthew Wilcox To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, 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: References: <20240819151512.2363698-1-surenb@google.com> <20240819151512.2363698-6-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: D7D8A1C0019 X-Stat-Signature: y43rqgehxgydiw8s9gny7ctppgdofmfn X-HE-Tag: 1724100059-854546 X-HE-Meta: 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 ZV5+F7PI CHu7Re1f1+mtH8QxkRbL2sCSxr28+umVeKtNxIIVcFSiQWxKvpN8FVWOUINV4Bm40Ur7nOp1QY8/EaAuL6c2J1VpapHRZXllfrdMeOjxe4pDDj2DSzXHj902klNfSJrJt2jFU6jMWy3iOOsD6moLCIKvaZHtLDmy4/VpFBDER9EJrI5/+HSuHfyfhp8YbQfxWCSNxqSDLZsWclvtCRVZNl7ck+gUMKqKe8K6d1t4T0GRwHP5cF3P8uOOiO7aH3o+dbYNQzm/rFxxbNQaOldbgSUmA1v2g0q93gNYHIDzXlS5OH6y0As1MyBbfQG7T4o7Ml+i2fU24guQNYAwytoWAoNYUMA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.006814, 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, 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.