x86/mm: Remove region_is_ram() call from ioremap

__ioremap_caller() calls region_is_ram() to walk through the
iomem_resource table to check if a target range is in RAM, which was
added to improve the lookup performance over page_is_ram() (commit
906e36c5c717 "x86: use optimized ioresource lookup in ioremap
function"). page_is_ram() was no longer used when this change was
added, though.

__ioremap_caller() then calls walk_system_ram_range(), which had
replaced page_is_ram() to improve the lookup performance (commit
c81c8a1eeede "x86, ioremap: Speed up check for RAM pages").

Since both checks walk through the same iomem_resource table for
the same purpose, there is no need to call both functions.

Aside of that walk_system_ram_range() is the only useful check at the
moment because region_is_ram() always returns -1 due to an
implementation bug. That bug in region_is_ram() cannot be fixed
without breaking existing ioremap callers, which rely on the subtle
difference of walk_system_ram_range() versus non page aligned ranges.

Once these offending callers are fixed we can use region_is_ram() and
remove walk_system_ram_range().

[ tglx: Massaged changelog ]

Signed-off-by: Toshi Kani <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Cc: Roland Dreier <[email protected]>
Cc: Mike Travis <[email protected]>
Cc: Luis R. Rodriguez <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

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