[PATCH] dax: add set_dax_nomc() and set_dax_nocache() stub helpers

[Arnd Bergmann <arnd@kernel.org>]

From: Arnd Bergmann <arnd@arndb.de>

In some randconfig builds, the IS_ERR() check appears to not get completely
eliminated, resulting in the compiler to insert references to these two
functions that cause a link failure:

ERROR: modpost: "set_dax_nocache" [drivers/md/dm-mod.ko] undefined!
ERROR: modpost: "set_dax_nomc" [drivers/md/dm-mod.ko] undefined!

Add more stub functions for the dax-disabled case here to make it build again.

Fixes: d888f6b0a766 ("dm: treat alloc_dax() -EOPNOTSUPP failure as non-fatal")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402160420.e4QKwoGO-lkp@intel.com/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 include/linux/dax.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/dax.h b/include/linux/dax.h
index df2d52b8a245..4527c10016fb 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -64,6 +64,9 @@ 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_synchronous(struct dax_device *dax_dev);
+void set_dax_nocache(struct dax_device *dax_dev);
+void set_dax_nomc(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);
 /*
@@ -108,6 +111,12 @@ static inline bool dax_synchronous(struct dax_device *dax_dev)
 static inline void set_dax_synchronous(struct dax_device *dax_dev)
 {
 }
+static inline void set_dax_nocache(struct dax_device *dax_dev)
+{
+}
+static inline void set_dax_nomc(struct dax_device *dax_dev)
+{
+}
 static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
 				struct dax_device *dax_dev)
 {
@@ -120,9 +129,6 @@ 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);
-- 
2.39.2