@@ -319,6 +319,11 @@ EXPORT_SYMBOL_GPL(dax_alive);
* that any fault handlers or operations that might have seen
* dax_alive(), have completed. Any operations that start after
* synchronize_srcu() has run will abort upon seeing !dax_alive().
+ *
+ * Note, because alloc_dax() returns an ERR_PTR() on error, callers
+ * typically store its result into a local variable in order to check
+ * the result. Therefore, care must be taken to populate the struct
+ * device dax_dev field make sure the dax_dev is not leaked.
*/
void kill_dax(struct dax_device *dax_dev)
{
@@ -445,6 +450,16 @@ 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,
+ * 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)))
+ return ERR_PTR(-EOPNOTSUPP);
+
if (WARN_ON_ONCE(ops && !ops->zero_page_range))
return ERR_PTR(-EINVAL);
@@ -56,7 +56,6 @@ endif # BLOCK
config FS_DAX
bool "File system based Direct Access (DAX) support"
depends on MMU
- depends on !(ARM || MIPS || SPARC)
depends on ZONE_DEVICE || FS_DAX_LIMITED
select FS_IOMAP
select DAX
@@ -86,11 +86,7 @@ static inline void *dax_holder(struct dax_device *dax_dev)
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;
+ return ERR_PTR(-EOPNOTSUPP);
}
static inline void put_dax(struct dax_device *dax_dev)
{
Replace the following fs/Kconfig:FS_DAX dependency: depends on !(ARM || MIPS || SPARC) By a runtime check within alloc_dax(). This runtime check returns ERR_PTR(-EOPNOTSUPP) if the @ops parameter is non-NULL (which means the kernel is using an aliased mapping) on an architecture which has data cache aliasing. Change the return value from NULL to PTR_ERR(-EOPNOTSUPP) for CONFIG_DAX=n for consistency. 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.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Russell King <linux@armlinux.org.uk> 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 --- drivers/dax/super.c | 15 +++++++++++++++ fs/Kconfig | 1 - include/linux/dax.h | 6 +----- 3 files changed, 16 insertions(+), 6 deletions(-)