percpu: fix build breakage on s390 and cleanup build configuration tests

Commit bbddff05 (percpu: use percpu allocator on UP too) incorrectly
excluded pcpu_build_alloc_info() on SMP configurations which use
generic setup_per_cpu_area() like s390.  The config ifdefs are
becoming confusing.  Fix and clean it up by,

* Move pcpu_build_alloc_info() right on top of its two users -
  pcpu_{embed|page}_first_chunk() which are already in CONFIG_SMP
  block.

* Define BUILD_{EMBED|PAGE}_FIRST_CHUNK which indicate whether each
  first chunk function needs to be included and use them to control
  inclusion of the three functions to reduce confusion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sachin Sant <sachinp@in.ibm.com>

1 files changed, 175 insertions, 163 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
index fa70122dfdd0..0cd4bf61012c 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1075,165 +1075,6 @@ 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
- * @dyn_size: minimum free size for dynamic allocation in bytes
- * @atom_size: allocation atom size
- * @cpu_distance_fn: callback to determine distance between cpus, optional
- *
- * This function determines grouping of units, their mappings to cpus
- * and other parameters considering needed percpu size, allocation
- * atom size and distances between CPUs.
- *
- * Groups are always mutliples of atom size and CPUs which are of
- * LOCAL_DISTANCE both ways are grouped together and share space for
- * units in the same group.  The returned configuration is guaranteed
- * to have CPUs on different nodes on different groups and >=75% usage
- * of allocated virtual address space.
- *
- * RETURNS:
- * On success, pointer to the new allocation_info is returned.  On
- * failure, ERR_PTR value is returned.
- */
-static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
-                                size_t reserved_size, size_t dyn_size,
-                                size_t atom_size,
-                                pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
-{
-        static int group_map[NR_CPUS] __initdata;
-        static int group_cnt[NR_CPUS] __initdata;
-        const size_t static_size = __per_cpu_end - __per_cpu_start;
-        int nr_groups = 1, nr_units = 0;
-        size_t size_sum, min_unit_size, alloc_size;
-        int upa, max_upa, uninitialized_var(best_upa);  /* units_per_alloc */
-        int last_allocs, group, unit;
-        unsigned int cpu, tcpu;
-        struct pcpu_alloc_info *ai;
-        unsigned int *cpu_map;
-
-        /* this function may be called multiple times */
-        memset(group_map, 0, sizeof(group_map));
-        memset(group_cnt, 0, sizeof(group_cnt));
-
-        /* calculate size_sum and ensure dyn_size is enough for early alloc */
-        size_sum = PFN_ALIGN(static_size + reserved_size +
-                            max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE));
-        dyn_size = size_sum - static_size - reserved_size;
-
-        /*
-         * Determine min_unit_size, alloc_size and max_upa such that
-         * alloc_size is multiple of atom_size and is the smallest
-         * which can accomodate 4k aligned segments which are equal to
-         * or larger than min_unit_size.
-         */
-        min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
-
-        alloc_size = roundup(min_unit_size, atom_size);
-        upa = alloc_size / min_unit_size;
-        while (alloc_size % upa || ((alloc_size / upa) & ~PAGE_MASK))
-                upa--;
-        max_upa = upa;
-
-        /* group cpus according to their proximity */
-        for_each_possible_cpu(cpu) {
-                group = 0;
-        next_group:
-                for_each_possible_cpu(tcpu) {
-                        if (cpu == tcpu)
-                                break;
-                        if (group_map[tcpu] == group && cpu_distance_fn &&
-                            (cpu_distance_fn(cpu, tcpu) > LOCAL_DISTANCE ||
-                             cpu_distance_fn(tcpu, cpu) > LOCAL_DISTANCE)) {
-                                group++;
-                                nr_groups = max(nr_groups, group + 1);
-                                goto next_group;
-                        }
-                }
-                group_map[cpu] = group;
-                group_cnt[group]++;
-        }
-
-        /*
-         * Expand unit size until address space usage goes over 75%
-         * and then as much as possible without using more address
-         * space.
-         */
-        last_allocs = INT_MAX;
-        for (upa = max_upa; upa; upa--) {
-                int allocs = 0, wasted = 0;
-
-                if (alloc_size % upa || ((alloc_size / upa) & ~PAGE_MASK))
-                        continue;
-
-                for (group = 0; group < nr_groups; group++) {
-                        int this_allocs = DIV_ROUND_UP(group_cnt[group], upa);
-                        allocs += this_allocs;
-                        wasted += this_allocs * upa - group_cnt[group];
-                }
-
-                /*
-                 * Don't accept if wastage is over 1/3.  The
-                 * greater-than comparison ensures upa==1 always
-                 * passes the following check.
-                 */
-                if (wasted > num_possible_cpus() / 3)
-                        continue;
-
-                /* and then don't consume more memory */
-                if (allocs > last_allocs)
-                        break;
-                last_allocs = allocs;
-                best_upa = upa;
-        }
-        upa = best_upa;
-
-        /* allocate and fill alloc_info */
-        for (group = 0; group < nr_groups; group++)
-                nr_units += roundup(group_cnt[group], upa);
-
-        ai = pcpu_alloc_alloc_info(nr_groups, nr_units);
-        if (!ai)
-                return ERR_PTR(-ENOMEM);
-        cpu_map = ai->groups[0].cpu_map;
-
-        for (group = 0; group < nr_groups; group++) {
-                ai->groups[group].cpu_map = cpu_map;
-                cpu_map += roundup(group_cnt[group], upa);
-        }
-
-        ai->static_size = static_size;
-        ai->reserved_size = reserved_size;
-        ai->dyn_size = dyn_size;
-        ai->unit_size = alloc_size / upa;
-        ai->atom_size = atom_size;
-        ai->alloc_size = alloc_size;
-
-        for (group = 0, unit = 0; group_cnt[group]; group++) {
-                struct pcpu_group_info *gi = &ai->groups[group];
-
-                /*
-                 * Initialize base_offset as if all groups are located
-                 * back-to-back.  The caller should update this to
-                 * reflect actual allocation.
-                 */
-                gi->base_offset = unit * ai->unit_size;
-
-                for_each_possible_cpu(cpu)
-                        if (group_map[cpu] == group)
-                                gi->cpu_map[gi->nr_units++] = cpu;
-                gi->nr_units = roundup(gi->nr_units, upa);
-                unit += gi->nr_units;
-        }
-        BUG_ON(unit != nr_units);
-
-        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
  * @lvl: loglevel
@@ -1532,8 +1373,180 @@ static int __init percpu_alloc_setup(char *str)
 }
 early_param("percpu_alloc", percpu_alloc_setup);
 
+/*
+ * pcpu_embed_first_chunk() is used by the generic percpu setup.
+ * Build it if needed by the arch config or the generic setup is going
+ * to be used.
+ */
 #if defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
         !defined(CONFIG_HAVE_SETUP_PER_CPU_AREA)
+#define BUILD_EMBED_FIRST_CHUNK
+#endif
+
+/* build pcpu_page_first_chunk() iff needed by the arch config */
+#if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
+#define BUILD_PAGE_FIRST_CHUNK
+#endif
+
+/* pcpu_build_alloc_info() is used by both embed and page first chunk */
+#if defined(BUILD_EMBED_FIRST_CHUNK) || defined(BUILD_PAGE_FIRST_CHUNK)
+/**
+ * pcpu_build_alloc_info - build alloc_info considering distances between CPUs
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @dyn_size: minimum free size for dynamic allocation in bytes
+ * @atom_size: allocation atom size
+ * @cpu_distance_fn: callback to determine distance between cpus, optional
+ *
+ * This function determines grouping of units, their mappings to cpus
+ * and other parameters considering needed percpu size, allocation
+ * atom size and distances between CPUs.
+ *
+ * Groups are always mutliples of atom size and CPUs which are of
+ * LOCAL_DISTANCE both ways are grouped together and share space for
+ * units in the same group.  The returned configuration is guaranteed
+ * to have CPUs on different nodes on different groups and >=75% usage
+ * of allocated virtual address space.
+ *
+ * RETURNS:
+ * On success, pointer to the new allocation_info is returned.  On
+ * failure, ERR_PTR value is returned.
+ */
+static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
+                                size_t reserved_size, size_t dyn_size,
+                                size_t atom_size,
+                                pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
+{
+        static int group_map[NR_CPUS] __initdata;
+        static int group_cnt[NR_CPUS] __initdata;
+        const size_t static_size = __per_cpu_end - __per_cpu_start;
+        int nr_groups = 1, nr_units = 0;
+        size_t size_sum, min_unit_size, alloc_size;
+        int upa, max_upa, uninitialized_var(best_upa);  /* units_per_alloc */
+        int last_allocs, group, unit;
+        unsigned int cpu, tcpu;
+        struct pcpu_alloc_info *ai;
+        unsigned int *cpu_map;
+
+        /* this function may be called multiple times */
+        memset(group_map, 0, sizeof(group_map));
+        memset(group_cnt, 0, sizeof(group_cnt));
+
+        /* calculate size_sum and ensure dyn_size is enough for early alloc */
+        size_sum = PFN_ALIGN(static_size + reserved_size +
+                            max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE));
+        dyn_size = size_sum - static_size - reserved_size;
+
+        /*
+         * Determine min_unit_size, alloc_size and max_upa such that
+         * alloc_size is multiple of atom_size and is the smallest
+         * which can accomodate 4k aligned segments which are equal to
+         * or larger than min_unit_size.
+         */
+        min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
+
+        alloc_size = roundup(min_unit_size, atom_size);
+        upa = alloc_size / min_unit_size;
+        while (alloc_size % upa || ((alloc_size / upa) & ~PAGE_MASK))
+                upa--;
+        max_upa = upa;
+
+        /* group cpus according to their proximity */
+        for_each_possible_cpu(cpu) {
+                group = 0;
+        next_group:
+                for_each_possible_cpu(tcpu) {
+                        if (cpu == tcpu)
+                                break;
+                        if (group_map[tcpu] == group && cpu_distance_fn &&
+                            (cpu_distance_fn(cpu, tcpu) > LOCAL_DISTANCE ||
+                             cpu_distance_fn(tcpu, cpu) > LOCAL_DISTANCE)) {
+                                group++;
+                                nr_groups = max(nr_groups, group + 1);
+                                goto next_group;
+                        }
+                }
+                group_map[cpu] = group;
+                group_cnt[group]++;
+        }
+
+        /*
+         * Expand unit size until address space usage goes over 75%
+         * and then as much as possible without using more address
+         * space.
+         */
+        last_allocs = INT_MAX;
+        for (upa = max_upa; upa; upa--) {
+                int allocs = 0, wasted = 0;
+
+                if (alloc_size % upa || ((alloc_size / upa) & ~PAGE_MASK))
+                        continue;
+
+                for (group = 0; group < nr_groups; group++) {
+                        int this_allocs = DIV_ROUND_UP(group_cnt[group], upa);
+                        allocs += this_allocs;
+                        wasted += this_allocs * upa - group_cnt[group];
+                }
+
+                /*
+                 * Don't accept if wastage is over 1/3.  The
+                 * greater-than comparison ensures upa==1 always
+                 * passes the following check.
+                 */
+                if (wasted > num_possible_cpus() / 3)
+                        continue;
+
+                /* and then don't consume more memory */
+                if (allocs > last_allocs)
+                        break;
+                last_allocs = allocs;
+                best_upa = upa;
+        }
+        upa = best_upa;
+
+        /* allocate and fill alloc_info */
+        for (group = 0; group < nr_groups; group++)
+                nr_units += roundup(group_cnt[group], upa);
+
+        ai = pcpu_alloc_alloc_info(nr_groups, nr_units);
+        if (!ai)
+                return ERR_PTR(-ENOMEM);
+        cpu_map = ai->groups[0].cpu_map;
+
+        for (group = 0; group < nr_groups; group++) {
+                ai->groups[group].cpu_map = cpu_map;
+                cpu_map += roundup(group_cnt[group], upa);
+        }
+
+        ai->static_size = static_size;
+        ai->reserved_size = reserved_size;
+        ai->dyn_size = dyn_size;
+        ai->unit_size = alloc_size / upa;
+        ai->atom_size = atom_size;
+        ai->alloc_size = alloc_size;
+
+        for (group = 0, unit = 0; group_cnt[group]; group++) {
+                struct pcpu_group_info *gi = &ai->groups[group];
+
+                /*
+                 * Initialize base_offset as if all groups are located
+                 * back-to-back.  The caller should update this to
+                 * reflect actual allocation.
+                 */
+                gi->base_offset = unit * ai->unit_size;
+
+                for_each_possible_cpu(cpu)
+                        if (group_map[cpu] == group)
+                                gi->cpu_map[gi->nr_units++] = cpu;
+                gi->nr_units = roundup(gi->nr_units, upa);
+                unit += gi->nr_units;
+        }
+        BUG_ON(unit != nr_units);
+
+        return ai;
+}
+#endif /* BUILD_EMBED_FIRST_CHUNK || BUILD_PAGE_FIRST_CHUNK */
+
+#if defined(BUILD_EMBED_FIRST_CHUNK)
 /**
  * pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
  * @reserved_size: the size of reserved percpu area in bytes
@@ -1662,10 +1675,9 @@ out_free:
                 free_bootmem(__pa(areas), areas_size);
         return rc;
 }
-#endif /* CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK ||
-          !CONFIG_HAVE_SETUP_PER_CPU_AREA */
+#endif /* BUILD_EMBED_FIRST_CHUNK */
 
-#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
+#ifdef BUILD_PAGE_FIRST_CHUNK
 /**
  * pcpu_page_first_chunk - map the first chunk using PAGE_SIZE pages
  * @reserved_size: the size of reserved percpu area in bytes
@@ -1773,7 +1785,7 @@ out_free_ar:
         pcpu_free_alloc_info(ai);
         return rc;
 }
-#endif /* CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK */
+#endif /* BUILD_PAGE_FIRST_CHUNK */
 
 #ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
 /*