Memory hotplug / ACPI: Simplify memory removal

Now that the memory offlining should be taken care of by the
companion device offlining code in acpi_scan_hot_remove(), the
ACPI memory hotplug driver doesn't need to offline it in
remove_memory() any more.  Moreover, since the return value of
remove_memory() is not used, it's better to make it be a void
function and trigger a BUG() if the memory scheduled for removal is
not offline.

Change the code in accordance with the above observations.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Toshi Kani <toshi.kani@hp.com>

3 files changed, 12 insertions, 74 deletions

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 5590db12028e..c711d1144044 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -271,13 +271,11 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
         return 0;
 }
 
-static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
+static void acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
 {
         acpi_handle handle = mem_device->device->handle;
-        int result = 0, nid;
         struct acpi_memory_info *info, *n;
-
-        nid = acpi_get_node(handle);
+        int nid = acpi_get_node(handle);
 
         list_for_each_entry_safe(info, n, &mem_device->res_list, list) {
                 if (!info->enabled)
@@ -287,15 +285,10 @@ static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
                         nid = memory_add_physaddr_to_nid(info->start_addr);
 
                 acpi_unbind_memory_blocks(info, handle);
-                result = remove_memory(nid, info->start_addr, info->length);
-                if (result)
-                        return result;
-
+                remove_memory(nid, info->start_addr, info->length);
                 list_del(&info->list);
                 kfree(info);
         }
-
-        return result;
 }
 
 static void acpi_memory_device_free(struct acpi_memory_device *mem_device)
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index ae5480a00963..00569fb4ed6a 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -252,7 +252,7 @@ extern int add_memory(int nid, u64 start, u64 size);
 extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
 extern bool is_memblock_offlined(struct memory_block *mem);
-extern int remove_memory(int nid, u64 start, u64 size);
+extern void remove_memory(int nid, u64 start, u64 size);
 extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
                                                                 int nr_pages);
 extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a39841d240e8..7026fbc42aaa 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1670,24 +1670,6 @@ int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-/**
- * 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 = device_offline(&mem->dev);
-
-        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);
@@ -1813,54 +1795,22 @@ void try_offline_node(int nid)
 }
 EXPORT_SYMBOL(try_offline_node);
 
-int __ref remove_memory(int nid, u64 start, u64 size)
+void __ref remove_memory(int nid, u64 start, u64 size)
 {
-        unsigned long start_pfn, end_pfn;
-        int ret = 0;
-        int retry = 1;
-
-        start_pfn = PFN_DOWN(start);
-        end_pfn = PFN_UP(start + size - 1);
-
-        /*
-         * 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;
-        }
+        int ret;
 
         lock_memory_hotplug();
 
         /*
-         * we have offlined all memory blocks like this:
-         *   1. lock memory hotplug
-         *   2. offline a memory block
-         *   3. unlock memory hotplug
-         *
-         * repeat step1-3 to offline the memory block. All memory blocks
-         * must be offlined before removing memory. But we don't hold the
-         * lock in the whole operation. So we should check whether all
-         * memory blocks are offlined.
+         * All memory blocks must be offlined before removing memory.  Check
+         * whether all memory blocks in question are offline and trigger a BUG()
+         * if this is not the case.
          */
-
-        ret = walk_memory_range(start_pfn, end_pfn, NULL,
+        ret = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL,
                                 is_memblock_offlined_cb);
         if (ret) {
                 unlock_memory_hotplug();
-                return ret;
+                BUG();
         }
 
         /* remove memmap entry */
@@ -1871,17 +1821,12 @@ repeat:
         try_offline_node(nid);
 
         unlock_memory_hotplug();
-
-        return 0;
 }
 #else
 int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 {
         return -EINVAL;
 }
-int remove_memory(int nid, u64 start, u64 size)
-{
-        return -EINVAL;
-}
+void remove_memory(int nid, u64 start, u64 size) {}
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 EXPORT_SYMBOL_GPL(remove_memory);