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b=tbRZUBYKZeGuGZqoaY1DeK0hJwQjx5z1KlX4+5BjG6KbY0Wk63ANlCvJNLNHlZa3q AUni6+/Zg3BIFSkr3VSAod2+wG4om/7ONygxmnx3R8qV4KfQsZwdwxR/mM07U628WQ k19fXtoHrvLwxdcINcsb5baXKobPg9DensK1+8QFljOtCtki8OcEMSaA14ImZIluOL HBFIytcfOMxaLatB6NbpkXRQ8dIHcmIw4+3c36ghJ2FkKfkT1jBw0k4BKfFjUoRMQW 0Hw8foVVlIlyyL8xJUMQOn7XN5Ij/6RqjdW4lVw7Nz7wr+wztv85CRKkRVtJejDGJn uUVzPSeTZ8zkg== Received: from thinkos.internal.efficios.com (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4TW5cf2nN2zY9Y; Thu, 8 Feb 2024 13:49:22 -0500 (EST) From: Mathieu Desnoyers To: Dan Williams , Arnd Bergmann , Dave Chinner Cc: linux-kernel@vger.kernel.org, Mathieu Desnoyers , Andrew Morton , Linus Torvalds , Vishal Verma , Dave Jiang , Matthew Wilcox , Russell King , linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, dm-devel@lists.linux.dev, nvdimm@lists.linux.dev, linux-s390@vger.kernel.org Subject: [PATCH v4 00/12] Introduce cpu_dcache_is_aliasing() to fix DAX regression Date: Thu, 8 Feb 2024 13:49:01 -0500 Message-Id: <20240208184913.484340-1-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.39.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790360794153685708 X-GMAIL-MSGID: 1790360794153685708 This commit introduced in v4.0 prevents building FS_DAX on 32-bit ARM, even on ARMv7 which does not have virtually aliased data caches: commit d92576f1167c ("dax: does not work correctly with virtual aliasing caches") It used to work fine before: I have customers using DAX over pmem on ARMv7, but this regression will likely prevent them from upgrading their kernel. The root of the issue here is the fact that DAX was never designed to handle virtually aliasing data caches (VIVT and VIPT with aliasing data cache). It touches the pages through their linear mapping, which is not consistent with the userspace mappings with virtually aliasing data caches. This patch series introduces cpu_dcache_is_aliasing() with the new Kconfig option ARCH_HAS_CPU_CACHE_ALIASING and implements it for all architectures. The implementation of cpu_dcache_is_aliasing() is either evaluated to a constant at compile-time or a runtime check, which is what is needed on ARM. With this we can basically narrow down the list of architectures which are unsupported by DAX to those which are really affected. Testing done so far: - Compile allyesconfig on x86-64, - Compile allyesconfig on x86-64, with FS_DAX=n. - Compile allyesconfig on x86-64, with DAX=n. - Boot test after modifying alloc_dax() to force returning -EOPNOTSUPP even on x86-64, thus simulating the behavior expected on an architecture with data cache aliasing. There are many more axes to test however. I would welcome Tested-by for: - affected architectures, - affected drivers, - affected filesytems. Thanks, Mathieu Changes since v3: - Fix a leak on dax_add_host() failure in nvdimm/pmem. - Split the series into a bissectable sequence of changes. - Ensure that device-dax use-cases still works on data cache aliasing architectures. Changes since v2: - Move DAX supported runtime check to alloc_dax(), - Modify DM to handle alloc_dax() error as non-fatal, - Remove all filesystem modifications, since the check is now done by alloc_dax(), - rename "dcache" and "cache" to "cpu dcache" and "cpu cache" to eliminate confusion with VFS terminology. Changes since v1: - The order of the series was completely changed based on the feedback received on v1, - cache_is_aliasing() is renamed to dcache_is_aliasing(), - ARCH_HAS_CACHE_ALIASING_DYNAMIC is gone, - dcache_is_aliasing() vs ARCH_HAS_CACHE_ALIASING relationship is simplified, - the dax_is_supported() check was moved to its rightful place in all filesystems. Cc: Andrew Morton Cc: Linus Torvalds Cc: Vishal Verma Cc: Dave Jiang Cc: Matthew Wilcox Cc: Russell King Cc: linux-arch@vger.kernel.org Cc: linux-cxl@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-xfs@vger.kernel.org Cc: dm-devel@lists.linux.dev Cc: nvdimm@lists.linux.dev Cc: linux-s390@vger.kernel.org Mathieu Desnoyers (12): nvdimm/pmem: Fix leak on dax_add_host() failure nvdimm/pmem: Treat alloc_dax() -EOPNOTSUPP failure as non-fatal dm: Treat alloc_dax() -EOPNOTSUPP failure as non-fatal dcssblk: Handle alloc_dax() -EOPNOTSUPP failure virtio: Treat alloc_dax() -EOPNOTSUPP failure as non-fatal dax: Check for data cache aliasing at runtime Introduce cpu_dcache_is_aliasing() across all architectures dax: Fix incorrect list of data cache aliasing architectures nvdimm/pmem: Cleanup alloc_dax() error handling dm: Cleanup alloc_dax() error handling dcssblk: Cleanup alloc_dax() error handling virtio: Cleanup alloc_dax() error handling arch/arc/Kconfig | 1 + arch/arc/include/asm/cachetype.h | 9 +++++++++ arch/arm/Kconfig | 1 + arch/arm/include/asm/cachetype.h | 2 ++ arch/csky/Kconfig | 1 + arch/csky/include/asm/cachetype.h | 9 +++++++++ arch/m68k/Kconfig | 1 + arch/m68k/include/asm/cachetype.h | 9 +++++++++ arch/mips/Kconfig | 1 + arch/mips/include/asm/cachetype.h | 9 +++++++++ arch/nios2/Kconfig | 1 + arch/nios2/include/asm/cachetype.h | 10 ++++++++++ arch/parisc/Kconfig | 1 + arch/parisc/include/asm/cachetype.h | 9 +++++++++ arch/sh/Kconfig | 1 + arch/sh/include/asm/cachetype.h | 9 +++++++++ arch/sparc/Kconfig | 1 + arch/sparc/include/asm/cachetype.h | 14 ++++++++++++++ arch/xtensa/Kconfig | 1 + arch/xtensa/include/asm/cachetype.h | 10 ++++++++++ drivers/dax/super.c | 14 ++++++++++++++ drivers/md/dm.c | 17 +++++++++-------- drivers/nvdimm/pmem.c | 23 ++++++++++++----------- drivers/s390/block/dcssblk.c | 11 ++++++----- fs/Kconfig | 1 - fs/fuse/virtio_fs.c | 15 +++++++++++---- include/linux/cacheinfo.h | 6 ++++++ include/linux/dax.h | 6 +----- mm/Kconfig | 6 ++++++ 29 files changed, 165 insertions(+), 34 deletions(-) create mode 100644 arch/arc/include/asm/cachetype.h create mode 100644 arch/csky/include/asm/cachetype.h create mode 100644 arch/m68k/include/asm/cachetype.h create mode 100644 arch/mips/include/asm/cachetype.h create mode 100644 arch/nios2/include/asm/cachetype.h create mode 100644 arch/parisc/include/asm/cachetype.h create mode 100644 arch/sh/include/asm/cachetype.h create mode 100644 arch/sparc/include/asm/cachetype.h create mode 100644 arch/xtensa/include/asm/cachetype.h