percpu: generalize first chunk allocator selection

Now that all first chunk allocators are in mm/percpu.c, it makes sense
to make generalize percpu_alloc kernel parameter.  Define PCPU_FC_*
and set pcpu_chosen_fc using early_param() in mm/percpu.c.  Arch code
can use the set value to determine which first chunk allocator to use.

Signed-off-by: Tejun Heo <tj@kernel.org>

4 files changed, 56 insertions, 23 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 12e9eb77ee0d..dee9ce2e6cfa 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1919,11 +1919,12 @@ and is between 256 and 4096 characters. It is defined in the file
                         Format: { 0 | 1 }
                         See arch/parisc/kernel/pdc_chassis.c
 
-        percpu_alloc=   [X86] Select which percpu first chunk allocator to use.
-                        Allowed values are one of "lpage", "embed" and "page".
-                        See comments in arch/x86/kernel/setup_percpu.c for
-                        details on each allocator.  This parameter is primarily
-                        for debugging and performance comparison.
+        percpu_alloc=   Select which percpu first chunk allocator to use.
+                        Currently supported values are "embed", "page" and
+                        "lpage".  Archs may support subset or none of the
+                        selections.  See comments in mm/percpu.c for details
+                        on each allocator.  This parameter is primarily for
+                        debugging and performance comparison.
 
         pf.             [PARIDE]
                         See Documentation/blockdev/paride.txt.
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 1e17711c29d6..b961d99e6416 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -267,16 +267,6 @@ static ssize_t __init setup_pcpu_page(size_t static_size)
                                      pcpup_populate_pte);
 }
 
-/* for explicit first chunk allocator selection */
-static char pcpu_chosen_alloc[16] __initdata;
-
-static int __init percpu_alloc_setup(char *str)
-{
-        strncpy(pcpu_chosen_alloc, str, sizeof(pcpu_chosen_alloc) - 1);
-        return 0;
-}
-early_param("percpu_alloc", percpu_alloc_setup);
-
 static inline void setup_percpu_segment(int cpu)
 {
 #ifdef CONFIG_X86_32
@@ -307,19 +297,17 @@ void __init setup_per_cpu_areas(void)
          * each allocator for details.
          */
         ret = -EINVAL;
-        if (strlen(pcpu_chosen_alloc)) {
-                if (strcmp(pcpu_chosen_alloc, "page")) {
-                        if (!strcmp(pcpu_chosen_alloc, "lpage"))
+        if (pcpu_chosen_fc != PCPU_FC_AUTO) {
+                if (pcpu_chosen_fc != PCPU_FC_PAGE) {
+                        if (pcpu_chosen_fc == PCPU_FC_LPAGE)
                                 ret = setup_pcpu_lpage(static_size, true);
-                        else if (!strcmp(pcpu_chosen_alloc, "embed"))
-                                ret = setup_pcpu_embed(static_size, true);
                         else
-                                pr_warning("PERCPU: unknown allocator %s "
-                                           "specified\n", pcpu_chosen_alloc);
+                                ret = setup_pcpu_embed(static_size, true);
+
                         if (ret < 0)
                                 pr_warning("PERCPU: %s allocator failed (%zd), "
                                            "falling back to page size\n",
-                                           pcpu_chosen_alloc, ret);
+                                           pcpu_fc_names[pcpu_chosen_fc], ret);
                 }
         } else {
                 ret = setup_pcpu_lpage(static_size, false);
diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index e26788e0da4a..9be05cbe5ee0 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -59,6 +59,18 @@
 extern void *pcpu_base_addr;
 extern const int *pcpu_unit_map;
 
+enum pcpu_fc {
+        PCPU_FC_AUTO,
+        PCPU_FC_EMBED,
+        PCPU_FC_PAGE,
+        PCPU_FC_LPAGE,
+
+        PCPU_FC_NR,
+};
+extern const char *pcpu_fc_names[PCPU_FC_NR];
+
+extern enum pcpu_fc pcpu_chosen_fc;
+
 typedef void * (*pcpu_fc_alloc_fn_t)(unsigned int cpu, size_t size);
 typedef void (*pcpu_fc_free_fn_t)(void *ptr, size_t size);
 typedef void (*pcpu_fc_populate_pte_fn_t)(unsigned long addr);
diff --git a/mm/percpu.c b/mm/percpu.c
index 7971997de310..7fb40bb1555a 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1414,6 +1414,38 @@ size_t __init pcpu_setup_first_chunk(size_t static_size, size_t reserved_size,
         return pcpu_unit_size;
 }
 
+const char *pcpu_fc_names[PCPU_FC_NR] __initdata = {
+        [PCPU_FC_AUTO]  = "auto",
+        [PCPU_FC_EMBED] = "embed",
+        [PCPU_FC_PAGE]  = "page",
+        [PCPU_FC_LPAGE] = "lpage",
+};
+
+enum pcpu_fc pcpu_chosen_fc __initdata = PCPU_FC_AUTO;
+
+static int __init percpu_alloc_setup(char *str)
+{
+        if (0)
+                /* nada */;
+#ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
+        else if (!strcmp(str, "embed"))
+                pcpu_chosen_fc = PCPU_FC_EMBED;
+#endif
+#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
+        else if (!strcmp(str, "page"))
+                pcpu_chosen_fc = PCPU_FC_PAGE;
+#endif
+#ifdef CONFIG_NEED_PER_CPU_LPAGE_FIRST_CHUNK
+        else if (!strcmp(str, "lpage"))
+                pcpu_chosen_fc = PCPU_FC_LPAGE;
+#endif
+        else
+                pr_warning("PERCPU: unknown allocator %s specified\n", str);
+
+        return 0;
+}
+early_param("percpu_alloc", percpu_alloc_setup);
+
 static inline size_t pcpu_calc_fc_sizes(size_t static_size,
                                         size_t reserved_size,
                                         ssize_t *dyn_sizep)