From: Mike Rapoport <r...@linux.ibm.com>

Some architectures (e.g. ARC) have the ZONE_HIGHMEM zone below the
ZONE_NORMAL. Allowing free_area_init() parse max_zone_pfn array even it is
sorted in descending order allows using free_area_init() on such
architectures.

Add top -> down traversal of max_zone_pfn array in free_area_init() and use
the latter in ARC node/zone initialization.

Signed-off-by: Mike Rapoport <r...@linux.ibm.com>
---
 arch/arc/mm/init.c | 36 +++++++-----------------------------
 mm/page_alloc.c    | 24 +++++++++++++++++++-----
 2 files changed, 26 insertions(+), 34 deletions(-)

diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index 0920c969c466..41eb9be1653c 100644
--- a/arch/arc/mm/init.c
+++ b/arch/arc/mm/init.c
@@ -63,11 +63,13 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 
size)
 
                low_mem_sz = size;
                in_use = 1;
+               memblock_add_node(base, size, 0);
        } else {
 #ifdef CONFIG_HIGHMEM
                high_mem_start = base;
                high_mem_sz = size;
                in_use = 1;
+               memblock_add_node(base, size, 1);
 #endif
        }
 
@@ -83,8 +85,7 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
  */
 void __init setup_arch_memory(void)
 {
-       unsigned long zones_size[MAX_NR_ZONES];
-       unsigned long zones_holes[MAX_NR_ZONES];
+       unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0 };
 
        init_mm.start_code = (unsigned long)_text;
        init_mm.end_code = (unsigned long)_etext;
@@ -115,7 +116,6 @@ void __init setup_arch_memory(void)
         * the crash
         */
 
-       memblock_add_node(low_mem_start, low_mem_sz, 0);
        memblock_reserve(CONFIG_LINUX_LINK_BASE,
                         __pa(_end) - CONFIG_LINUX_LINK_BASE);
 
@@ -133,22 +133,7 @@ void __init setup_arch_memory(void)
        memblock_dump_all();
 
        /*----------------- node/zones setup --------------------------*/
-       memset(zones_size, 0, sizeof(zones_size));
-       memset(zones_holes, 0, sizeof(zones_holes));
-
-       zones_size[ZONE_NORMAL] = max_low_pfn - min_low_pfn;
-       zones_holes[ZONE_NORMAL] = 0;
-
-       /*
-        * We can't use the helper free_area_init(zones[]) because it uses
-        * PAGE_OFFSET to compute the @min_low_pfn which would be wrong
-        * when our kernel doesn't start at PAGE_OFFSET, i.e.
-        * PAGE_OFFSET != CONFIG_LINUX_RAM_BASE
-        */
-       free_area_init_node(0,                  /* node-id */
-                           zones_size,         /* num pages per zone */
-                           min_low_pfn,        /* first pfn of node */
-                           zones_holes);       /* holes */
+       max_zone_pfn[ZONE_NORMAL] = max_low_pfn;
 
 #ifdef CONFIG_HIGHMEM
        /*
@@ -168,20 +153,13 @@ void __init setup_arch_memory(void)
        min_high_pfn = PFN_DOWN(high_mem_start);
        max_high_pfn = PFN_DOWN(high_mem_start + high_mem_sz);
 
-       zones_size[ZONE_NORMAL] = 0;
-       zones_holes[ZONE_NORMAL] = 0;
-
-       zones_size[ZONE_HIGHMEM] = max_high_pfn - min_high_pfn;
-       zones_holes[ZONE_HIGHMEM] = 0;
-
-       free_area_init_node(1,                  /* node-id */
-                           zones_size,         /* num pages per zone */
-                           min_high_pfn,       /* first pfn of node */
-                           zones_holes);       /* holes */
+       max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn;
 
        high_memory = (void *)(min_high_pfn << PAGE_SHIFT);
        kmap_init();
 #endif
+
+       free_area_init(max_zone_pfn);
 }
 
 /*
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d35ca0996a09..98a47f90065a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7408,7 +7408,8 @@ static void check_for_memory(pg_data_t *pgdat, int nid)
 void __init free_area_init(unsigned long *max_zone_pfn)
 {
        unsigned long start_pfn, end_pfn;
-       int i, nid;
+       int i, nid, zone;
+       bool descending = false;
 
        /* Record where the zone boundaries are */
        memset(arch_zone_lowest_possible_pfn, 0,
@@ -7418,13 +7419,26 @@ void __init free_area_init(unsigned long *max_zone_pfn)
 
        start_pfn = find_min_pfn_with_active_regions();
 
+       /*
+        * Some architecturs, e.g. ARC may have ZONE_HIGHMEM below
+        * ZONE_NORMAL. For such cases we allow max_zone_pfn sorted in the
+        * descending order
+        */
+       if (MAX_NR_ZONES > 1 && max_zone_pfn[0] > max_zone_pfn[1])
+               descending = true;
+
        for (i = 0; i < MAX_NR_ZONES; i++) {
-               if (i == ZONE_MOVABLE)
+               if (descending)
+                       zone = MAX_NR_ZONES - i - 1;
+               else
+                       zone = i;
+
+               if (zone == ZONE_MOVABLE)
                        continue;
 
-               end_pfn = max(max_zone_pfn[i], start_pfn);
-               arch_zone_lowest_possible_pfn[i] = start_pfn;
-               arch_zone_highest_possible_pfn[i] = end_pfn;
+               end_pfn = max(max_zone_pfn[zone], start_pfn);
+               arch_zone_lowest_possible_pfn[zone] = start_pfn;
+               arch_zone_highest_possible_pfn[zone] = end_pfn;
 
                start_pfn = end_pfn;
        }
-- 
2.26.1


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