Re: [PATCH 1/10] memory-hotplug : check whether memory is offline or not when removing memory
From: KOSAKI Motohiro <hidden>
Date: 2012-10-05 19:33:44
Also in:
linux-acpi, linux-mm, linux-s390, linux-sh, lkml, sparclinux
On Thu, Oct 4, 2012 at 10:25 PM, Yasuaki Ishimatsu [off-list ref] wrote:
When calling remove_memory(), the memory should be offline. If the function is used to online memory, kernel panic may occur. So the patch checks whether memory is offline or not.
You don't explain WHY we need the check.
quoted hunk ↗ jump to hunk
CC: David Rientjes <rientjes@google.com> CC: Jiang Liu <redacted> CC: Len Brown <redacted> CC: Christoph Lameter <redacted> Cc: Minchan Kim <redacted> CC: Andrew Morton <akpm@linux-foundation.org> CC: KOSAKI Motohiro <redacted> Signed-off-by: Wen Congyang <redacted> Signed-off-by: Yasuaki Ishimatsu <redacted> --- drivers/base/memory.c | 39 +++++++++++++++++++++++++++++++++++++++ include/linux/memory.h | 5 +++++ mm/memory_hotplug.c | 17 +++++++++++++++-- 3 files changed, 59 insertions(+), 2 deletions(-) Index: linux-3.6/drivers/base/memory.c ===================================================================--- linux-3.6.orig/drivers/base/memory.c 2012-10-04 14:22:57.000000000 +0900 +++ linux-3.6/drivers/base/memory.c 2012-10-04 14:45:46.653585860 +0900@@ -70,6 +70,45 @@ void unregister_memory_isolate_notifier( } EXPORT_SYMBOL(unregister_memory_isolate_notifier); +bool is_memblk_offline(unsigned long start, unsigned long size)
Don't use memblk. Usually memblk mean struct numa_meminfo for x86/numa. Maybe memory_range_offlined() is better. And, this function don't take struct memory_block, then this file may be no good place. And you need to write down function comment.
quoted hunk ↗ jump to hunk
+{ + struct memory_block *mem = NULL; + struct mem_section *section; + unsigned long start_pfn, end_pfn; + unsigned long pfn, section_nr; + + start_pfn = PFN_DOWN(start); + end_pfn = PFN_UP(start + size); + + 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; + if (mem->state == MEM_OFFLINE) + continue; + + kobject_put(&mem->dev.kobj); + return false; + } + + if (mem) + kobject_put(&mem->dev.kobj); + + return true; +} +EXPORT_SYMBOL(is_memblk_offline); + /* * register_memory - Setup a sysfs device for a memory block */ Index: linux-3.6/include/linux/memory.h ===================================================================--- linux-3.6.orig/include/linux/memory.h 2012-10-02 18:00:22.000000000 +0900 +++ linux-3.6/include/linux/memory.h 2012-10-04 14:44:40.902581028 +0900@@ -106,6 +106,10 @@ static inline int memory_isolate_notify( { return 0; } +static inline bool is_memblk_offline(unsigned long start, unsigned long size) +{ + return false; +} #else extern int register_memory_notifier(struct notifier_block *nb); extern void unregister_memory_notifier(struct notifier_block *nb);@@ -120,6 +124,7 @@ extern int memory_isolate_notify(unsigne extern struct memory_block *find_memory_block_hinted(struct mem_section *, struct memory_block *); extern struct memory_block *find_memory_block(struct mem_section *); +extern bool is_memblk_offline(unsigned long start, unsigned long size); #define CONFIG_MEM_BLOCK_SIZE (PAGES_PER_SECTION<<PAGE_SHIFT) enum mem_add_context { BOOT, HOTPLUG }; #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */Index: linux-3.6/mm/memory_hotplug.c ===================================================================--- linux-3.6.orig/mm/memory_hotplug.c 2012-10-04 14:31:08.000000000 +0900 +++ linux-3.6/mm/memory_hotplug.c 2012-10-04 14:58:22.449687986 +0900@@ -1045,8 +1045,21 @@ int offline_memory(u64 start, u64 size) int remove_memory(int nid, u64 start, u64 size) {
Your remove_memory() don't remove anything. that's strange.
- /* It is not implemented yet*/
- return 0;
+ int ret = 0;
+ lock_memory_hotplug();
+ /*
+ * The memory might become online by other task, even if you offine it.
+ * So we check whether the memory has been onlined or not.
+ */
+ if (!is_memblk_offline(start, size)) {
+ pr_warn("memory removing [mem %#010llx-%#010llx] failed, "
+ "because the memmory range is online\n",
+ start, start + size);No good warning. You should output which memory block can't be offlined, I think.
+ ret = -EAGAIN; + } + + unlock_memory_hotplug(); + return ret; } EXPORT_SYMBOL_GPL(remove_memory); #else -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>