commit d92576f1167c ("dax: does not work correctly with virtual aliasing caches") prevents DAX from building on architectures with virtually aliased dcache with:
depends on !(ARM || MIPS || SPARC) This check is too broad (e.g. recent ARMv7 don't have virtually aliased dcaches), and also misses many other architectures with virtually aliased data cache. This is a regression introduced in the v4.0 Linux kernel where the dax mount option is removed for 32-bit ARMv7 boards which have no data cache aliasing, and therefore should work fine with FS_DAX. This was turned into the following check in alloc_dax() by a preparatory change: if (ops && (IS_ENABLED(CONFIG_ARM) || IS_ENABLED(CONFIG_MIPS) || IS_ENABLED(CONFIG_SPARC))) return NULL; Use cpu_dcache_is_aliasing() instead to figure out whether the environment has aliasing data caches. Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches") Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> Reviewed-by: Dan Williams <dan.j.willi...@intel.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Dan Williams <dan.j.willi...@intel.com> Cc: Vishal Verma <vishal.l.ve...@intel.com> Cc: Dave Jiang <dave.ji...@intel.com> Cc: Matthew Wilcox <wi...@infradead.org> Cc: Arnd Bergmann <a...@arndb.de> Cc: Russell King <li...@armlinux.org.uk> Cc: linux-a...@vger.kernel.org Cc: linux-...@vger.kernel.org Cc: linux-fsde...@vger.kernel.org Cc: linux...@kvack.org Cc: linux-...@vger.kernel.org Cc: dm-devel@lists.linux.dev Cc: nvd...@lists.linux.dev --- drivers/dax/super.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/dax/super.c b/drivers/dax/super.c index ce5bffa86bba..a21a7c262382 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -13,6 +13,7 @@ #include <linux/uio.h> #include <linux/dax.h> #include <linux/fs.h> +#include <linux/cacheinfo.h> #include "dax-private.h" /** @@ -455,9 +456,7 @@ struct dax_device *alloc_dax(void *private, const struct dax_operations *ops) * except for device-dax (NULL operations pointer), which does * not use aliased mappings from the kernel. */ - if (ops && (IS_ENABLED(CONFIG_ARM) || - IS_ENABLED(CONFIG_MIPS) || - IS_ENABLED(CONFIG_SPARC))) + if (ops && cpu_dcache_is_aliasing()) return ERR_PTR(-EOPNOTSUPP); if (WARN_ON_ONCE(ops && !ops->zero_page_range)) -- 2.39.2