When calling __generic_fsdax_supported(), a dax-unsupported device may not have dax_dev as NULL, e.g. the dax related code block is not enabled by Kconfig. Therefore in __generic_fsdax_supported(), to check whether a device supports DAX or not, the following order should be performed, - If dax_dev pointer is NULL, it means the device driver explicitly announce it doesn't support DAX. Then it is OK to directly return false from __generic_fsdax_supported(). - If dax_dev pointer is NOT NULL, it might be because the driver doesn't support DAX and not explicitly initialize related data structure. Then bdev_dax_supported() should be called for further check. IMHO if device driver desn't explicitly set its dax_dev pointer to NULL, this is not a bug. Calling bdev_dax_supported() makes sure they can be recognized as dax-unsupported eventually. This patch does the following change for the above purpose, - if (!dax_dev && !bdev_dax_supported(bdev, blocksize)) { + if (!dax_dev || !bdev_dax_supported(bdev, blocksize)) { Fixes: c2affe920b0e ("dax: do not print error message for non-persistent memory block device") Signed-off-by: Coly Li <colyli(a)suse.de&gt; Reviewed-and-Tested-by: Adrian Huang <ahuang12(a)lenovo.com&gt; Cc: Ira Weiny <ira.weiny(a)intel.com&gt; Cc: Jan Kara <jack(a)suse.com&gt; Cc: Mike Snitzer <snitzer(a)redhat.com&gt; Cc: Pankaj Gupta <pankaj.gupta.linux(a)gmail.com&gt; Cc: Vishal Verma <vishal.l.verma(a)intel.com&gt; --- Changelog: v2: add Reviewed-and-Tested-by from Adrian Huang. v1: initial version. drivers/dax/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dax/super.c b/drivers/dax/super.c index 32642634c1bb..e5767c83ea23 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -100,7 +100,7 @@ bool __generic_fsdax_supported(struct dax_device *dax_dev, return false; } - if (!dax_dev && !bdev_dax_supported(bdev, blocksize)) { + if (!dax_dev || !bdev_dax_supported(bdev, blocksize)) { pr_debug("%s: error: dax unsupported by block device\n", bdevname(bdev, buf)); return false; --