dax: add a sysfs knob to control memmap_on_memory behavior

Add a sysfs knob for dax devices to control the memmap_on_memory setting
if the dax device were to be hotplugged as system memory.

The default memmap_on_memory setting for dax devices originating via pmem
or hmem is set to 'false' - i.e.  no memmap_on_memory semantics, to
preserve legacy behavior.  For dax devices via CXL, the default is on. 
The sysfs control allows the administrator to override the above defaults
if needed.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Vishal Verma <[email protected]>
Tested-by: Li Zhijian <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Huang, Ying <[email protected]>
Reviewed-by: Alison Schofield <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Oscar Salvador <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions