dax: fix detection of dax support for non-persistent memory block devices

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 of operations 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.

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.

Fixes: c2affe920b ("dax: do not print error message for non-persistent memory block device")
Cc: Jan Kara <jack@suse.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-and-tested-by: Adrian Huang <ahuang12@lenovo.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/20200903161625.19524-1-colyli@suse.de
This commit is contained in:
Coly Li 2020-09-04 00:16:25 +08:00 коммит произвёл Vishal Verma
Родитель c2affe920b
Коммит 6180bb446a
1 изменённых файлов: 1 добавлений и 1 удалений

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@ -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;