Mathieu Desnoyers wrote: > Replace the following fs/Kconfig:FS_DAX dependency: > > depends on !(ARM || MIPS || SPARC) > > By a runtime check within alloc_dax(). > > This is done in preparation for its use by each filesystem supporting > the "dax" mount option to validate whether DAX is indeed supported. > > This is done in preparation for using cpu_dcache_is_aliasing() in a > following change which will properly support architectures which detect > data cache aliasing at runtime. > > Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing > caches") > Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> > Cc: Andrew Morton <a...@linux-foundation.org> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: linux...@kvack.org > Cc: linux-a...@vger.kernel.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: nvd...@lists.linux.dev > Cc: linux-...@vger.kernel.org > Cc: linux-fsde...@vger.kernel.org > Cc: dm-devel@lists.linux.dev > --- > drivers/dax/super.c | 6 ++++++ > fs/Kconfig | 1 - > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/dax/super.c b/drivers/dax/super.c > index 0da9232ea175..e9f397b8a5a3 100644 > --- a/drivers/dax/super.c > +++ b/drivers/dax/super.c > @@ -445,6 +445,12 @@ struct dax_device *alloc_dax(void *private, const struct > dax_operations *ops) > dev_t devt; > int minor; > > + /* Unavailable on architectures with virtually aliased data caches. */ > + if (IS_ENABLED(CONFIG_ARM) || > + IS_ENABLED(CONFIG_MIPS) || > + IS_ENABLED(CONFIG_SPARC)) > + return NULL;
This function returns ERR_PTR(), not NULL on failure. ...and I notice this mistake is also made in include/linux/dax.h in the CONFIG_DAX=n case. That function also mentions: static inline struct dax_device *alloc_dax(void *private, const struct dax_operations *ops) { /* * Callers should check IS_ENABLED(CONFIG_DAX) to know if this * NULL is an error or expected. */ return NULL; } ...and none of the callers validate the result, but now runtime validation is necessary. I.e. it is not enough to check IS_ENABLED(CONFIG_DAX) it also needs to check cpu_dcache_is_aliasing(). With that, there are a few more fixup places needed, pmem_attach_disk(), dcssblk_add_store(), and virtio_fs_setup_dax().