Hi Wen,

2012/07/06 18:20, Wen Congyang wrote:

At 07/06/2012 04:27 PM, Yasuaki Ishimatsu Wrote:

quoted

Hi Wen,

2012/07/04 19:01, Wen Congyang wrote:

quoted

At 07/04/2012 01:52 PM, Yasuaki Ishimatsu Wrote:

quoted

Hi Wen,

2012/07/04 14:08, Wen Congyang wrote:

quoted

At 07/04/2012 12:45 PM, Yasuaki Ishimatsu Wrote:

quoted

Hi Wen,

2012/07/03 15:35, Wen Congyang wrote:

quoted

At 07/03/2012 01:56 PM, Yasuaki Ishimatsu Wrote:

quoted

When (hot)adding memory into system, /sys/firmware/memmap/X/{end, start, type}
sysfs files are created. But there is no code to remove these files. The patch
implements the function to remove them.

Note : The code does not free firmware_map_entry since there is no way to free
           memory which is allocated by bootmem.

CC: David Rientjes <rientjes@google.com>
CC: Jiang Liu <redacted>
CC: Len Brown <redacted>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <redacted>
CC: Christoph Lameter <redacted>
Cc: Minchan Kim <redacted>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <redacted>
Signed-off-by: Yasuaki Ishimatsu <redacted>

---
     drivers/firmware/memmap.c    |   70 +++++++++++++++++++++++++++++++++++++++++++
     include/linux/firmware-map.h |    6 +++
     mm/memory_hotplug.c          |    6 +++
     3 files changed, 81 insertions(+), 1 deletion(-)

Index: linux-3.5-rc4/mm/memory_hotplug.c
===================================================================

--- linux-3.5-rc4.orig/mm/memory_hotplug.c	2012-07-03 14:22:00.190240794 +0900
+++ linux-3.5-rc4/mm/memory_hotplug.c	2012-07-03 14:22:03.549198802 +0900

@@ -661,7 +661,11 @@ EXPORT_SYMBOL_GPL(add_memory);

     int remove_memory(int nid, u64 start, u64 size)
     {
-	return -EBUSY;
+	lock_memory_hotplug();
+	/* remove memmap entry */
+	firmware_map_remove(start, start + size - 1, "System RAM");
+	unlock_memory_hotplug();
+	return 0;

     }
     EXPORT_SYMBOL_GPL(remove_memory);

Index: linux-3.5-rc4/include/linux/firmware-map.h
===================================================================

--- linux-3.5-rc4.orig/include/linux/firmware-map.h	2012-07-03 14:21:45.766421116 +0900
+++ linux-3.5-rc4/include/linux/firmware-map.h	2012-07-03 14:22:03.550198789 +0900

@@ -25,6 +25,7 @@

     int firmware_map_add_early(u64 start, u64 end, const char *type);
     int firmware_map_add_hotplug(u64 start, u64 end, const char *type);
+int firmware_map_remove(u64 start, u64 end, const char *type);

     #else /* CONFIG_FIRMWARE_MEMMAP */

@@ -38,6 +39,11 @@ static inline int firmware_map_add_hotpl
     	return 0;
     }

+static inline int firmware_map_remove(u64 start, u64 end, const char *type)
+{
+	return 0;
+}
+
     #endif /* CONFIG_FIRMWARE_MEMMAP */

     #endif /* _LINUX_FIRMWARE_MAP_H */

Index: linux-3.5-rc4/drivers/firmware/memmap.c
===================================================================

--- linux-3.5-rc4.orig/drivers/firmware/memmap.c	2012-07-03 14:21:45.761421180 +0900
+++ linux-3.5-rc4/drivers/firmware/memmap.c	2012-07-03 14:22:03.569198549 +0900

@@ -79,7 +79,16 @@ static const struct sysfs_ops memmap_att
     	.show = memmap_attr_show,
     };

+static void release_firmware_map_entry(struct kobject *kobj)
+{
+	/*
+	 * FIXME : There is no idea.
+	 *         How to free the entry which allocated bootmem?
+	 */

I find a function free_bootmem(), but I am not sure whether it can work here.

It cannot work here.

quoted

Another problem: how to check whether the entry uses bootmem?

When firmware_map_entry is allocated by kzalloc(), the page has PG_slab.

This is not true. In my test, I find the page does not have PG_slab sometimes.

I think that it depends on the allocated size. firmware_map_entry size is
smaller than PAGE_SIZE. So the page has PG_Slab.

In my test, I add printk in the function firmware_map_add_hotplug() to display
page's flags. And sometimes the page is not allocated by slab(I use PageSlab()
to verify it).

How did you check it? Could you send your debug patch?

When the memory is not allocated from slab, the flags is 0x10000000008000.

Thank you for sending the patch.
I think the page to not have PageSlab is a compound page. So we can check
whether the entry is allocate from bootmem or not as follow:

static void release_firmware_map_entry(struct kobject *kobj)
{
	struct firmware_map_entry *entry = to_memmap_entry(kobj);
	struct page *head_page;

	head_page = virt_to_head_page(entry);
	if (PageSlab(head_page))
		kfree(etnry);
	else
		/* the entry is allocated from bootmem */
}

Thanks,
Yasuaki Ishimatsu