5 files changed, 66 insertions, 41 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index f4e516e9c37c..01a57447a410 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -301,3 +301,11 @@ config NOMMU_INITIAL_TRIM_EXCESS
           of 1 says that all excess pages should be trimmed.
 
           See Documentation/nommu-mmap.txt for more information.
+
+#
+# UP and nommu archs use km based percpu allocator
+#
+config NEED_PER_CPU_KM
+        depends on !SMP
+        bool
+        default y
diff --git a/mm/Makefile b/mm/Makefile
index 34b2546a9e37..f73f75a29f82 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -11,7 +11,7 @@ obj-y			:= bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
                            maccess.o page_alloc.o page-writeback.o \
                            readahead.o swap.o truncate.o vmscan.o shmem.o \
                            prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
-                           page_isolation.o mm_init.o mmu_context.o \
+                           page_isolation.o mm_init.o mmu_context.o percpu.o \
                            $(mmu-y)
 obj-y += init-mm.o
 
@@ -36,11 +36,6 @@ obj-$(CONFIG_FAILSLAB) += failslab.o
 obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
 obj-$(CONFIG_FS_XIP) += filemap_xip.o
 obj-$(CONFIG_MIGRATION) += migrate.o
-ifdef CONFIG_SMP
-obj-y += percpu.o
-else
-obj-y += percpu_up.o
-endif
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
 obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
diff --git a/mm/percpu-km.c b/mm/percpu-km.c
index df680855540a..7037bc73bfa4 100644
--- a/mm/percpu-km.c
+++ b/mm/percpu-km.c
@@ -27,7 +27,7 @@
  *   chunk size is not aligned.  percpu-km code will whine about it.
  */
 
-#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
+#if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
 #error "contiguous percpu allocation is incompatible with paged first chunk"
 #endif
 
diff --git a/mm/percpu.c b/mm/percpu.c
index 58c572b18b07..fa70122dfdd0 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -76,6 +76,7 @@
 #define PCPU_SLOT_BASE_SHIFT            5       /* 1-31 shares the same slot */
 #define PCPU_DFL_MAP_ALLOC              16      /* start a map with 16 ents */
 
+#ifdef CONFIG_SMP
 /* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
 #ifndef __addr_to_pcpu_ptr
 #define __addr_to_pcpu_ptr(addr)                                        \
@@ -89,6 +90,11 @@
                          (unsigned long)pcpu_base_addr -                \
                          (unsigned long)__per_cpu_start)
 #endif
+#else   /* CONFIG_SMP */
+/* on UP, it's always identity mapped */
+#define __addr_to_pcpu_ptr(addr)        (void __percpu *)(addr)
+#define __pcpu_ptr_to_addr(ptr)         (void __force *)(ptr)
+#endif  /* CONFIG_SMP */
 
 struct pcpu_chunk {
         struct list_head        list;           /* linked to pcpu_slot lists */
@@ -949,6 +955,7 @@ EXPORT_SYMBOL_GPL(free_percpu);
  */
 bool is_kernel_percpu_address(unsigned long addr)
 {
+#ifdef CONFIG_SMP
         const size_t static_size = __per_cpu_end - __per_cpu_start;
         void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
         unsigned int cpu;
@@ -959,6 +966,8 @@ bool is_kernel_percpu_address(unsigned long addr)
                 if ((void *)addr >= start && (void *)addr < start + static_size)
                         return true;
         }
+#endif
+        /* on UP, can't distinguish from other static vars, always false */
         return false;
 }
 
@@ -1066,6 +1075,8 @@ void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai)
         free_bootmem(__pa(ai), ai->__ai_size);
 }
 
+#if defined(CONFIG_SMP) && (defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
+                            defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK))
 /**
  * pcpu_build_alloc_info - build alloc_info considering distances between CPUs
  * @reserved_size: the size of reserved percpu area in bytes
@@ -1220,6 +1231,8 @@ static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
 
         return ai;
 }
+#endif  /* CONFIG_SMP && (CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK ||
+                          CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) */
 
 /**
  * pcpu_dump_alloc_info - print out information about pcpu_alloc_info
@@ -1363,7 +1376,9 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
 
         /* sanity checks */
         PCPU_SETUP_BUG_ON(ai->nr_groups <= 0);
+#ifdef CONFIG_SMP
         PCPU_SETUP_BUG_ON(!ai->static_size);
+#endif
         PCPU_SETUP_BUG_ON(!base_addr);
         PCPU_SETUP_BUG_ON(ai->unit_size < size_sum);
         PCPU_SETUP_BUG_ON(ai->unit_size & ~PAGE_MASK);
@@ -1488,6 +1503,8 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
         return 0;
 }
 
+#ifdef CONFIG_SMP
+
 const char *pcpu_fc_names[PCPU_FC_NR] __initdata = {
         [PCPU_FC_AUTO]  = "auto",
         [PCPU_FC_EMBED] = "embed",
@@ -1758,8 +1775,9 @@ out_free_ar:
 }
 #endif /* CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK */
 
+#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
 /*
- * Generic percpu area setup.
+ * Generic SMP percpu area setup.
  *
  * The embedding helper is used because its behavior closely resembles
  * the original non-dynamic generic percpu area setup.  This is
@@ -1770,7 +1788,6 @@ out_free_ar:
  * on the physical linear memory mapping which uses large page
  * mappings on applicable archs.
  */
-#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
 EXPORT_SYMBOL(__per_cpu_offset);
 
@@ -1799,13 +1816,48 @@ void __init setup_per_cpu_areas(void)
                                     PERCPU_DYNAMIC_RESERVE, PAGE_SIZE, NULL,
                                     pcpu_dfl_fc_alloc, pcpu_dfl_fc_free);
         if (rc < 0)
-                panic("Failed to initialized percpu areas.");
+                panic("Failed to initialize percpu areas.");
 
         delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
         for_each_possible_cpu(cpu)
                 __per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
 }
-#endif /* CONFIG_HAVE_SETUP_PER_CPU_AREA */
+#endif  /* CONFIG_HAVE_SETUP_PER_CPU_AREA */
+
+#else   /* CONFIG_SMP */
+
+/*
+ * UP percpu area setup.
+ *
+ * UP always uses km-based percpu allocator with identity mapping.
+ * Static percpu variables are indistinguishable from the usual static
+ * variables and don't require any special preparation.
+ */
+void __init setup_per_cpu_areas(void)
+{
+        const size_t unit_size =
+                roundup_pow_of_two(max_t(size_t, PCPU_MIN_UNIT_SIZE,
+                                         PERCPU_DYNAMIC_RESERVE));
+        struct pcpu_alloc_info *ai;
+        void *fc;
+
+        ai = pcpu_alloc_alloc_info(1, 1);
+        fc = __alloc_bootmem(unit_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
+        if (!ai || !fc)
+                panic("Failed to allocate memory for percpu areas.");
+
+        ai->dyn_size = unit_size;
+        ai->unit_size = unit_size;
+        ai->atom_size = unit_size;
+        ai->alloc_size = unit_size;
+        ai->groups[0].nr_units = 1;
+        ai->groups[0].cpu_map[0] = 0;
+
+        if (pcpu_setup_first_chunk(ai, fc) < 0)
+                panic("Failed to initialize percpu areas.");
+}
+
+#endif  /* CONFIG_SMP */
 
 /*
  * First and reserved chunks are initialized with temporary allocation
diff --git a/mm/percpu_up.c b/mm/percpu_up.c
deleted file mode 100644
index db884fae5721..000000000000
--- a/mm/percpu_up.c
+++ /dev/null
@@ -1,30 +0,0 @@
-/*
- * mm/percpu_up.c - dummy percpu memory allocator implementation for UP
- */
-
-#include <linux/module.h>
-#include <linux/percpu.h>
-#include <linux/slab.h>
-
-void __percpu *__alloc_percpu(size_t size, size_t align)
-{
-        /*
-         * Can't easily make larger alignment work with kmalloc.  WARN
-         * on it.  Larger alignment should only be used for module
-         * percpu sections on SMP for which this path isn't used.
-         */
-        WARN_ON_ONCE(align > SMP_CACHE_BYTES);
-        return (void __percpu __force *)kzalloc(size, GFP_KERNEL);
-}
-EXPORT_SYMBOL_GPL(__alloc_percpu);
-
-void free_percpu(void __percpu *p)
-{
-        kfree(this_cpu_ptr(p));
-}
-EXPORT_SYMBOL_GPL(free_percpu);
-
-phys_addr_t per_cpu_ptr_to_phys(void *addr)
-{
-        return __pa(addr);
-}