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 <toshi.kani@hp.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Roland Dreier <roland@purestorage.com>
Cc: Mike Travis <travis@sgi.com>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/1437088996-28511-3-git-send-email-toshi.kani@hp.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 6 insertions, 18 deletions

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index fd3df0ddb4d4..b9d4a33017fd 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -92,7 +92,6 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
         pgprot_t prot;
         int retval;
         void __iomem *ret_addr;
-        int ram_region;
 
         /* Don't allow wraparound or zero size */
         last_addr = phys_addr + size - 1;
@@ -115,26 +114,15 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
         /*
          * Don't allow anybody to remap normal RAM that we're using..
          */
-        /* First check if whole region can be identified as RAM or not */
-        ram_region = region_is_ram(phys_addr, size);
-        if (ram_region > 0) {
-                WARN_ONCE(1, "ioremap on RAM at 0x%lx - 0x%lx\n",
-                                (unsigned long int)phys_addr,
-                                (unsigned long int)last_addr);
-                return NULL;
-        }
-
-        /* If could not be identified(-1), check page by page */
-        if (ram_region < 0) {
-                pfn      = phys_addr >> PAGE_SHIFT;
-                last_pfn = last_addr >> PAGE_SHIFT;
-                if (walk_system_ram_range(pfn, last_pfn - pfn + 1, NULL,
+        pfn      = phys_addr >> PAGE_SHIFT;
+        last_pfn = last_addr >> PAGE_SHIFT;
+        if (walk_system_ram_range(pfn, last_pfn - pfn + 1, NULL,
                                           __ioremap_check_ram) == 1) {
-                        WARN_ONCE(1, "ioremap on RAM at 0x%llx - 0x%llx\n",
+                WARN_ONCE(1, "ioremap on RAM at 0x%llx - 0x%llx\n",
                                         phys_addr, last_addr);
-                        return NULL;
-                }
+                return NULL;
         }
+
         /*
          * Mappings have to be page-aligned
          */