[SPARC64]: Fix ugly dependency on NR_CPUS being a power-of-2.

The page->flags D-cache dirty state tracking depended upon
NR_CPUS being a power-of-2 via it's "NR_CPUS - 1" masking.

Fix that to use a fixed (256 - 1) mask as that is the limit
imposed by thread_info->cpu which is a "u8".

Finally, add a compile time check that NR_CPUS is not greater
than 256.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 6 deletions

diff --git a/arch/sparc64/mm/init.c b/arch/sparc64/mm/init.c
index 8fc413cb6acd..3fbaf342a452 100644
--- a/arch/sparc64/mm/init.c
+++ b/arch/sparc64/mm/init.c
@@ -121,15 +121,24 @@ __inline__ void flush_dcache_page_impl(struct page *page)
 }
 
 #define PG_dcache_dirty         PG_arch_1
+#define PG_dcache_cpu_shift     24
+#define PG_dcache_cpu_mask      (256 - 1)
+
+#if NR_CPUS > 256
+#error D-cache dirty tracking and thread_info->cpu need fixing for > 256 cpus
+#endif
 
 #define dcache_dirty_cpu(page) \
-        (((page)->flags >> 24) & (NR_CPUS - 1UL))
+        (((page)->flags >> PG_dcache_cpu_shift) & PG_dcache_cpu_mask)
 
 static __inline__ void set_dcache_dirty(struct page *page, int this_cpu)
 {
         unsigned long mask = this_cpu;
-        unsigned long non_cpu_bits = ~((NR_CPUS - 1UL) << 24UL);
-        mask = (mask << 24) | (1UL << PG_dcache_dirty);
+        unsigned long non_cpu_bits;
+
+        non_cpu_bits = ~(PG_dcache_cpu_mask << PG_dcache_cpu_shift);
+        mask = (mask << PG_dcache_cpu_shift) | (1UL << PG_dcache_dirty);
+
         __asm__ __volatile__("1:\n\t"
                              "ldx       [%2], %%g7\n\t"
                              "and       %%g7, %1, %%g1\n\t"
@@ -151,7 +160,7 @@ static __inline__ void clear_dcache_dirty_cpu(struct page *page, unsigned long c
         __asm__ __volatile__("! test_and_clear_dcache_dirty\n"
                              "1:\n\t"
                              "ldx       [%2], %%g7\n\t"
-                             "srlx      %%g7, 24, %%g1\n\t"
+                             "srlx      %%g7, %4, %%g1\n\t"
                              "and       %%g1, %3, %%g1\n\t"
                              "cmp       %%g1, %0\n\t"
                              "bne,pn    %%icc, 2f\n\t"
@@ -164,7 +173,8 @@ static __inline__ void clear_dcache_dirty_cpu(struct page *page, unsigned long c
                              "2:"
                              : /* no outputs */
                              : "r" (cpu), "r" (mask), "r" (&page->flags),
-                               "i" (NR_CPUS - 1UL)
+                               "i" (PG_dcache_cpu_mask),
+                               "i" (PG_dcache_cpu_shift)
                              : "g1", "g7");
 }
 
@@ -180,7 +190,8 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t p
         if (pfn_valid(pfn) &&
             (page = pfn_to_page(pfn), page_mapping(page)) &&
             ((pg_flags = page->flags) & (1UL << PG_dcache_dirty))) {
-                int cpu = ((pg_flags >> 24) & (NR_CPUS - 1UL));
+                int cpu = ((pg_flags >> PG_dcache_cpu_shift) &
+                           PG_dcache_cpu_mask);
                 int this_cpu = get_cpu();
 
                 /* This is just to optimize away some function calls