[PATCH 1/1] mm/percpu.c: correct max_distance calculation for pcpu_embed_first_chunk()

[zijun_hu]

From: zijun_hu <zijun...@htc.com>

correct max_distance from (base of the highest group + ai->unit_size)
to (base of the highest group + the group size)

Signed-off-by: zijun_hu <zijun...@htc.com>
---
 mm/percpu.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index fcaaac977954..ee0d1c93f070 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1963,7 +1963,8 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, 
size_t dyn_size,
        void *base = (void *)ULONG_MAX;
        void **areas = NULL;
        struct pcpu_alloc_info *ai;
-       size_t size_sum, areas_size, max_distance;
+       size_t size_sum, areas_size;
+       unsigned long max_distance;
        int group, i, rc;
 
        ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
@@ -2025,17 +2026,18 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, 
size_t dyn_size,
        }
 
        /* base address is now known, determine group base offsets */
-       max_distance = 0;
+       i = 0;
        for (group = 0; group < ai->nr_groups; group++) {
                ai->groups[group].base_offset = areas[group] - base;
-               max_distance = max_t(size_t, max_distance,
-                                    ai->groups[group].base_offset);
+               if (areas[group] > areas[i])
+                       i = group;
        }
-       max_distance += ai->unit_size;
+       max_distance = ai->groups[i].base_offset +
+               (unsigned long)ai->unit_size * ai->groups[i].nr_units;
 
        /* warn if maximum distance is further than 75% of vmalloc space */
        if (max_distance > VMALLOC_TOTAL * 3 / 4) {
-               pr_warn("max_distance=0x%zx too large for vmalloc space 
0x%lx\n",
+               pr_warn("max_distance=0x%lx too large for vmalloc space 
0x%lx\n",
                        max_distance, VMALLOC_TOTAL);
 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
                /* and fail if we have fallback */
-- 
1.9.1