Re: [RFC PATCH v4 4/13] memory-hotplug : remove /sys/firmware/memmap/X sysfs

Hi Wen,

2012/07/18 19:33, Wen Congyang wrote:

At 07/18/2012 06:09 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>
CC: Wen Congyang <redacted>
Signed-off-by: Yasuaki Ishimatsu <redacted>

---
  drivers/firmware/memmap.c    |   78 ++++++++++++++++++++++++++++++++++++++++++-
  include/linux/firmware-map.h |    6 +++
  mm/memory_hotplug.c          |    9 +++-
  3 files changed, 90 insertions(+), 3 deletions(-)

Index: linux-3.5-rc6/mm/memory_hotplug.c
===================================================================

--- linux-3.5-rc6.orig/mm/memory_hotplug.c	2012-07-18 17:20:05.670024283 +0900
+++ linux-3.5-rc6/mm/memory_hotplug.c	2012-07-18 17:51:03.933189930 +0900

@@ -1012,9 +1012,9 @@ int offline_memory(u64 start, u64 size)
  	return offline_pages(start_pfn, end_pfn, 120 * HZ);
  }
  
-int remove_memory(int nid, u64 start, u64 size)
+int __ref remove_memory(int nid, u64 start, u64 size)
  {
-	int ret = -EBUSY;
+	int ret = 0;
  	lock_memory_hotplug();
  	/*
  	 * The memory might become online by other task, even if you offine it.

@@ -1025,8 +1025,13 @@ int remove_memory(int nid, u64 start, u6
  			"because the memmory range is online\n",
  			start, start + size);
  		ret = -EAGAIN;
+		goto out;
  	}
  
+	/* remove memmap entry */
+	firmware_map_remove(start, start + size, "System RAM");
+
+out:
  	unlock_memory_hotplug();
  	return ret;
  

Index: linux-3.5-rc6/include/linux/firmware-map.h
===================================================================

--- linux-3.5-rc6.orig/include/linux/firmware-map.h	2012-07-18 17:19:37.007382563 +0900
+++ linux-3.5-rc6/include/linux/firmware-map.h	2012-07-18 17:42:20.804730245 +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-rc6/drivers/firmware/memmap.c
===================================================================

--- linux-3.5-rc6.orig/drivers/firmware/memmap.c	2012-07-18 17:19:43.618300182 +0900
+++ linux-3.5-rc6/drivers/firmware/memmap.c	2012-07-18 17:42:20.846729721 +0900

@@ -21,6 +21,7 @@
  #include <linux/types.h>
  #include <linux/bootmem.h>
  #include <linux/slab.h>
+#include <linux/mm.h>
  
  /*
   * Data types ------------------------------------------------------------------

@@ -79,7 +80,22 @@ static const struct sysfs_ops memmap_att
  	.show = memmap_attr_show,
  };
  
+#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
+
+static void release_firmware_map_entry(struct kobject *kobj)
+{
+	struct firmware_map_entry *entry = to_memmap_entry(kobj);
+	struct page *page;
+
+	page = virt_to_page(entry);
+	if (PageSlab(page) || PageCompound(page))
+		kfree(entry);

IIRC, this function's implementation is changed. Why do you do it?
If PageCompound(page), should we check page->first_page's flags?

I forgot to write the change to change log. Jiang and Christoph discussed
how to find the slab page:

- https://lkml.org/lkml/2012/7/6/333

Then, Christoph proposed this method.  So I changed it.

Thanks,
Yasuaki Ishimatsu

Thanks
Wen Congyang

quoted

+
+	/* There is no way to free memory allocated from bootmem*/
+}
+
  static struct kobj_type memmap_ktype = {
+	.release	= release_firmware_map_entry,
  	.sysfs_ops	= &memmap_attr_ops,
  	.default_attrs	= def_attrs,
  };

@@ -123,6 +139,16 @@ static int firmware_map_add_entry(u64 st
  	return 0;
  }
  
+/**
+ * firmware_map_remove_entry() - Does the real work to remove a firmware
+ * memmap entry.
+ * @entry: removed entry.
+ **/
+static inline void firmware_map_remove_entry(struct firmware_map_entry *entry)
+{
+	list_del(&entry->list);
+}
+
  /*
   * Add memmap entry on sysfs
   */

@@ -144,6 +170,31 @@ static int add_sysfs_fw_map_entry(struct
  	return 0;
  }
  
+/*
+ * Remove memmap entry on sysfs
+ */
+static inline void remove_sysfs_fw_map_entry(struct firmware_map_entry *entry)
+{
+	kobject_put(&entry->kobj);
+}
+
+/*
+ * Search memmap entry
+ */
+
+struct firmware_map_entry * __meminit
+find_firmware_map_entry(u64 start, u64 end, const char *type)
+{
+	struct firmware_map_entry *entry;
+
+	list_for_each_entry(entry, &map_entries, list)
+		if ((entry->start == start) && (entry->end == end) &&
+		    (!strcmp(entry->type, type)))
+			return entry;
+
+	return NULL;
+}
+
  /**
   * firmware_map_add_hotplug() - Adds a firmware mapping entry when we do
   * memory hotplug.

@@ -196,6 +247,32 @@ int __init firmware_map_add_early(u64 st
  	return firmware_map_add_entry(start, end, type, entry);
  }
  
+/**
+ * firmware_map_remove() - remove a firmware mapping entry
+ * @start: Start of the memory range.
+ * @end:   End of the memory range.
+ * @type:  Type of the memory range.
+ *
+ * removes a firmware mapping entry.
+ *
+ * Returns 0 on success, or -EINVAL if no entry.
+ **/
+int __meminit firmware_map_remove(u64 start, u64 end, const char *type)
+{
+	struct firmware_map_entry *entry;
+
+	entry = find_firmware_map_entry(start, end - 1, type);
+	if (!entry)
+		return -EINVAL;
+
+	firmware_map_remove_entry(entry);
+
+	/* remove the memmap entry */
+	remove_sysfs_fw_map_entry(entry);
+
+	return 0;
+}
+
  /*
   * Sysfs functions -------------------------------------------------------------
   */

@@ -218,7 +295,6 @@ static ssize_t type_show(struct firmware
  }
  
  #define to_memmap_attr(_attr) container_of(_attr, struct memmap_attribute, attr)
-#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
  
  static ssize_t memmap_attr_show(struct kobject *kobj,
  				struct attribute *attr, char *buf)

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