x86: query dynamic DEBUG_PAGEALLOC setting

x86: query dynamic DEBUG_PAGEALLOC setting

We can use debug_pagealloc_enabled() to check if we can map the identity
mapping with 2MB pages.  We can also add the state into the dump_stack
output.

The patch does not touch the code for the 1GB pages, which ignored
CONFIG_DEBUG_PAGEALLOC.  Do we need to fence this as well?

Signed-off-by: Christian Borntraeger <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Heiko Carstens <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>