alloc_tag: support for page allocation tag compression

Implement support for storing page allocation tag references directly in
the page flags instead of page extensions.  sysctl.vm.mem_profiling boot
parameter it extended to provide a way for a user to request this mode. 
Enabling compression eliminates memory overhead caused by page_ext and
results in better performance for page allocations.  However this mode
will not work if the number of available page flag bits is insufficient to
address all kernel allocations.  Such condition can happen during boot or
when loading a module.  If this condition is detected, memory allocation
profiling gets disabled with an appropriate warning.  By default
compression mode is disabled.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Suren Baghdasaryan <[email protected]>
Reviewed-by: Pasha Tatashin <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov (AMD) <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Daniel Gomez <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kalesh Singh <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Luis Chamberlain <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport (Microsoft) <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Petr Pavlu <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Sami Tolvanen <[email protected]>
Cc: Sourav Panda <[email protected]>
Cc: Steven Rostedt (Google) <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Thomas Huth <[email protected]>
Cc: Uladzislau Rezki (Sony) <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Xiongwei Song <[email protected]>
Cc: Yu Zhao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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