memblock: Add arch function to control coalescing of memblock memory regions

Some archs such as ARM want to avoid coalescing accross things such
as the lowmem/highmem boundary or similar. This provides the option
to control it via an arch callback for which a weak default is provided
which always allows coalescing.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 20 insertions, 1 deletions

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 150be938b910..e5e8f9db3a84 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -72,6 +72,8 @@ extern void memblock_dump_all(void);
 
 /* Provided by the architecture */
 extern phys_addr_t memblock_nid_range(phys_addr_t start, phys_addr_t end, int *nid);
+extern int memblock_memory_can_coalesce(phys_addr_t addr1, phys_addr_t size1,
+                                   phys_addr_t addr2, phys_addr_t size2);
 
 /**
  * memblock_set_current_limit - Set the current allocation limit to allow
diff --git a/mm/memblock.c b/mm/memblock.c
index 0787790b1ce0..8715f09434df 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -241,6 +241,12 @@ static int memblock_double_array(struct memblock_type *type)
         return 0;
 }
 
+extern int __weak memblock_memory_can_coalesce(phys_addr_t addr1, phys_addr_t size1,
+                                          phys_addr_t addr2, phys_addr_t size2)
+{
+        return 1;
+}
+
 static long memblock_add_region(struct memblock_type *type, phys_addr_t base, phys_addr_t size)
 {
         unsigned long coalesced = 0;
@@ -262,6 +268,10 @@ static long memblock_add_region(struct memblock_type *type, phys_addr_t base, ph
                         return 0;
 
                 adjacent = memblock_addrs_adjacent(base, size, rgnbase, rgnsize);
+                /* Check if arch allows coalescing */
+                if (adjacent != 0 && type == &memblock.memory &&
+                    !memblock_memory_can_coalesce(base, size, rgnbase, rgnsize))
+                        break;
                 if (adjacent > 0) {
                         type->regions[i].base -= size;
                         type->regions[i].size += size;
@@ -274,7 +284,14 @@ static long memblock_add_region(struct memblock_type *type, phys_addr_t base, ph
                 }
         }
 
-        if ((i < type->cnt - 1) && memblock_regions_adjacent(type, i, i+1)) {
+        /* If we plugged a hole, we may want to also coalesce with the
+         * next region
+         */
+        if ((i < type->cnt - 1) && memblock_regions_adjacent(type, i, i+1) &&
+            ((type != &memblock.memory || memblock_memory_can_coalesce(type->regions[i].base,
+                                                             type->regions[i].size,
+                                                             type->regions[i+1].base,
+                                                             type->regions[i+1].size)))) {
                 memblock_coalesce_regions(type, i, i+1);
                 coalesced++;
         }