dax: add fsdev_dax_from_file()

If the file is a fsdev_dax open, take the dax_dev from the device inode's
i_cdev.  Return with a reference grabbed on the private dax inode.

Make dax_dev_get() static again (internal to super.c for alloc_dax), export
fsdev_dax_from_file() instead.

This fix is in response to a Sashiko review, and some subsequent analysis.

About the 'fixes' tag: this removes the export of dax_dev_get(), which was
flawed, and replaces it with fsdev_dax_from_file(). It feels like the fixes
tag makes sense for correcting an ABI error.

Fixes: 2ae624d5a555d ("dax: export dax_dev_get()")
Originally-by: John Groves <john@groves.net>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Gregory Price (Meta) <gourry@gourry.net>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

0 files changed, 0 insertions, 0 deletions