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[49.181.38.249]) by smtp.gmail.com with ESMTPSA id r6-20020a056a00216600b006dbd79596f3sm8582748pff.160.2024.01.30.18.48.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jan 2024 18:48:43 -0800 (PST) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1rV0eW-00HZlT-1P; Wed, 31 Jan 2024 13:48:40 +1100 Date: Wed, 31 Jan 2024 13:48:40 +1100 From: Dave Chinner To: Mathieu Desnoyers Cc: Dan Williams , Vishal Verma , Dave Jiang , linux-kernel@vger.kernel.org, Andrew Morton , Linus Torvalds , linux-mm@kvack.org, linux-arch@vger.kernel.org, Matthew Wilcox , Arnd Bergmann , Russell King , linux-cxl@vger.kernel.org, nvdimm@lists.linux.dev, linux-xfs@vger.kernel.org Subject: Re: [RFC PATCH v2 7/8] Introduce dcache_is_aliasing() across all architectures Message-ID: References: <20240130165255.212591-1-mathieu.desnoyers@efficios.com> <20240130165255.212591-8-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240130165255.212591-8-mathieu.desnoyers@efficios.com> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 3F7FA40002 X-Stat-Signature: 7ofy5dguzjxd7jpyd7z8xhg9kya6k9uf X-Rspam-User: X-HE-Tag: 1706669325-500266 X-HE-Meta: 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 hanVLa3p 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000013, 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 Tue, Jan 30, 2024 at 11:52:54AM -0500, Mathieu Desnoyers wrote: > Introduce a generic way to query whether the dcache is virtually aliased > on all architectures. Its purpose is to ensure that subsystems which > are incompatible with virtually aliased data caches (e.g. FS_DAX) can > reliably query this. > > For dcache aliasing, there are three scenarios dependending on the > architecture. Here is a breakdown based on my understanding: > > A) The dcache is always aliasing: > > * arc > * csky > * m68k (note: shared memory mappings are incoherent ? SHMLBA is missing there.) > * sh > * parisc /me wonders why the dentry cache aliasing has problems on these systems. Oh, dcache != fs/dcache.c (the VFS dentry cache). Can you please rename this function appropriately so us dumb filesystem people don't confuse cpu data cache configurations with the VFS dentry cache aliasing when we read this code? Something like cpu_dcache_is_aliased(), perhaps? -Dave. -- Dave Chinner david@fromorbit.com