archive mirror
 help / color / mirror / Atom feed
* [PATCH v3] dax: fix for do not print error message for non-persistent memory block device
@ 2020-09-03 16:04 Coly Li
  0 siblings, 0 replies; only message in thread
From: Coly Li @ 2020-09-03 16:04 UTC (permalink / raw)
  To: linux-nvdimm
  Cc: dm-devel, Coly Li, Adrian Huang, Mike Snitzer, Pankaj Gupta, Jan Kara

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 <>
Reviewed-and-Tested-by: Adrian Huang <>
Reviewed-by: Mike Snitzer <>
Reviewed-by: Pankaj Gupta <>
Cc: Ira Weiny <>
Cc: Jan Kara <>
Cc: Vishal Verma <>
v3: add more Reviewed-by from Mike Snitzer and Pankaj Gupta.
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;
Linux-nvdimm mailing list --
To unsubscribe send an email to

^ permalink raw reply related	[flat|nested] only message in thread

only message in thread, other threads:[~2020-09-03 16:05 UTC | newest]

Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-03 16:04 [PATCH v3] dax: fix for do not print error message for non-persistent memory block device Coly Li

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).