From 2807c54b3809ca5e51e5a9dfa5e9ddb8993a0e6f Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 15 Feb 2024 09:46:25 -0500 Subject: [PATCH] dax: add empty static inline for CONFIG_DAX=n Patch series "Introduce cpu_dcache_is_aliasing() to fix DAX regression", v6. 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") Even though it used to work fine before. 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. This patch (of 9): When building a kernel with CONFIG_DAX=n, all uses of set_dax_nocache() and set_dax_nomc() need to be either within regions of code or compile units which are explicitly not compiled, or they need to rely on compiler optimizations to eliminate calls to those undefined symbols. It appears that at least the openrisc and loongarch architectures don't end up eliminating those undefined symbols even if they are provably within code which is eliminated due to conditional branches depending on constants. Implement empty static inline functions for set_dax_nocache() and set_dax_nomc() in CONFIG_DAX=n to ensure those undefined references are removed. Link: https://lkml.kernel.org/r/20240215144633.96437-1-mathieu.desnoyers@efficios.com Link: https://lkml.kernel.org/r/20240215144633.96437-2-mathieu.desnoyers@efficios.com Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202402140037.wGfA1kqX-lkp@intel.com/ Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202402131351.a0FZOgEG-lkp@intel.com/ Fixes: 7ac5360cd4d0 ("dax: remove the copy_from_iter and copy_to_iter methods") Signed-off-by: Mathieu Desnoyers Cc: Christoph Hellwig Cc: Dan Williams Cc: Vishal Verma Cc: Dave Jiang Cc: Matthew Wilcox Cc: Arnd Bergmann Cc: Russell King Cc: Dave Chinner Cc: Michael Sclafani Cc: Alasdair Kergon Cc: Heiko Carstens Cc: Mike Snitzer Cc: Mikulas Patocka Signed-off-by: Andrew Morton --- include/linux/dax.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/include/linux/dax.h b/include/linux/dax.h index b463502b16e1..e3ffe7c7f01d 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -63,6 +63,8 @@ void kill_dax(struct dax_device *dax_dev); void dax_write_cache(struct dax_device *dax_dev, bool wc); bool dax_write_cache_enabled(struct dax_device *dax_dev); bool dax_synchronous(struct dax_device *dax_dev); +void set_dax_nocache(struct dax_device *dax_dev); +void set_dax_nomc(struct dax_device *dax_dev); void set_dax_synchronous(struct dax_device *dax_dev); size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i); @@ -109,6 +111,12 @@ static inline bool dax_synchronous(struct dax_device *dax_dev) { return true; } +static inline void set_dax_nocache(struct dax_device *dax_dev) +{ +} +static inline void set_dax_nomc(struct dax_device *dax_dev) +{ +} static inline void set_dax_synchronous(struct dax_device *dax_dev) { } @@ -124,9 +132,6 @@ static inline size_t dax_recovery_write(struct dax_device *dax_dev, } #endif -void set_dax_nocache(struct dax_device *dax_dev); -void set_dax_nomc(struct dax_device *dax_dev); - struct writeback_control; #if defined(CONFIG_BLOCK) && defined(CONFIG_FS_DAX) int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk);