memory-hotplug: remove redundant codes

offlining memory blocks and checking whether memory blocks are offlined
are very similar.  This patch introduces a new function to remove
redundant codes.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Reviewed-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jiang Liu <jiang.liu@huawei.com>
Cc: Jianguo Wu <wujianguo@huawei.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Wu Jianguo <wujianguo@huawei.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 82 insertions, 47 deletions

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 5d350f5c68e5..e5b91b12cec3 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1380,20 +1380,26 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
         return __offline_pages(start_pfn, start_pfn + nr_pages, 120 * HZ);
 }
 
-int remove_memory(u64 start, u64 size)
+/**
+ * walk_memory_range - walks through all mem sections in [start_pfn, end_pfn)
+ * @start_pfn: start pfn of the memory range
+ * @end_pfn: end pft of the memory range
+ * @arg: argument passed to func
+ * @func: callback for each memory section walked
+ *
+ * This function walks through all present mem sections in range
+ * [start_pfn, end_pfn) and call func on each mem section.
+ *
+ * Returns the return value of func.
+ */
+static int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
+                void *arg, int (*func)(struct memory_block *, void *))
 {
         struct memory_block *mem = NULL;
         struct mem_section *section;
-        unsigned long start_pfn, end_pfn;
         unsigned long pfn, section_nr;
         int ret;
-        int return_on_error = 0;
-        int retry = 0;
-
-        start_pfn = PFN_DOWN(start);
-        end_pfn = start_pfn + PFN_DOWN(size);
 
-repeat:
         for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
                 section_nr = pfn_to_section_nr(pfn);
                 if (!present_section_nr(section_nr))
@@ -1410,22 +1416,76 @@ repeat:
                 if (!mem)
                         continue;
 
-                ret = offline_memory_block(mem);
+                ret = func(mem, arg);
                 if (ret) {
-                        if (return_on_error) {
-                                kobject_put(&mem->dev.kobj);
-                                return ret;
-                        } else {
-                                retry = 1;
-                        }
+                        kobject_put(&mem->dev.kobj);
+                        return ret;
                 }
         }
 
         if (mem)
                 kobject_put(&mem->dev.kobj);
 
-        if (retry) {
-                return_on_error = 1;
+        return 0;
+}
+
+/**
+ * offline_memory_block_cb - callback function for offlining memory block
+ * @mem: the memory block to be offlined
+ * @arg: buffer to hold error msg
+ *
+ * Always return 0, and put the error msg in arg if any.
+ */
+static int offline_memory_block_cb(struct memory_block *mem, void *arg)
+{
+        int *ret = arg;
+        int error = offline_memory_block(mem);
+
+        if (error != 0 && *ret == 0)
+                *ret = error;
+
+        return 0;
+}
+
+static int is_memblock_offlined_cb(struct memory_block *mem, void *arg)
+{
+        int ret = !is_memblock_offlined(mem);
+
+        if (unlikely(ret))
+                pr_warn("removing memory fails, because memory "
+                        "[%#010llx-%#010llx] is onlined\n",
+                        PFN_PHYS(section_nr_to_pfn(mem->start_section_nr)),
+                        PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1))-1);
+
+        return ret;
+}
+
+int remove_memory(u64 start, u64 size)
+{
+        unsigned long start_pfn, end_pfn;
+        int ret = 0;
+        int retry = 1;
+
+        start_pfn = PFN_DOWN(start);
+        end_pfn = start_pfn + PFN_DOWN(size);
+
+        /*
+         * When CONFIG_MEMCG is on, one memory block may be used by other
+         * blocks to store page cgroup when onlining pages. But we don't know
+         * in what order pages are onlined. So we iterate twice to offline
+         * memory:
+         * 1st iterate: offline every non primary memory block.
+         * 2nd iterate: offline primary (i.e. first added) memory block.
+         */
+repeat:
+        walk_memory_range(start_pfn, end_pfn, &ret,
+                          offline_memory_block_cb);
+        if (ret) {
+                if (!retry)
+                        return ret;
+
+                retry = 0;
+                ret = 0;
                 goto repeat;
         }
 
@@ -1443,38 +1503,13 @@ repeat:
          * memory blocks are offlined.
          */
 
-        mem = NULL;
-        for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
-                section_nr = pfn_to_section_nr(pfn);
-                if (!present_section_nr(section_nr))
-                        continue;
-
-                section = __nr_to_section(section_nr);
-                /* same memblock? */
-                if (mem)
-                        if ((section_nr >= mem->start_section_nr) &&
-                            (section_nr <= mem->end_section_nr))
-                                continue;
-
-                mem = find_memory_block_hinted(section, mem);
-                if (!mem)
-                        continue;
-
-                ret = is_memblock_offlined(mem);
-                if (!ret) {
-                        pr_warn("removing memory fails, because memory "
-                                "[%#010llx-%#010llx] is onlined\n",
-                                PFN_PHYS(section_nr_to_pfn(mem->start_section_nr)),
-                                PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1)) - 1);
-
-                        kobject_put(&mem->dev.kobj);
-                        unlock_memory_hotplug();
-                        return ret;
-                }
+        ret = walk_memory_range(start_pfn, end_pfn, NULL,
+                                is_memblock_offlined_cb);
+        if (ret) {
+                unlock_memory_hotplug();
+                return ret;
         }
 
-        if (mem)
-                kobject_put(&mem->dev.kobj);
         unlock_memory_hotplug();
 
         return 0;