Re: [PATCH] Add "removable" to /sysfs to show memblock removability

[Badari Pulavarty <pbadari@us.ibm.com>]

On Thu, 2007-10-25 at 15:45 -0700, Dave Hansen wrote:
> On Thu, 2007-10-25 at 15:35 -0700, Badari Pulavarty wrote:
> > 
> > +static ssize_t show_mem_removable(struct sys_device *dev, char *buf)
> > +{
> > +       unsigned long start_pfn;
> > +       struct memory_block *mem =
> > +               container_of(dev, struct memory_block, sysdev);
> > +
> > +       start_pfn = section_nr_to_pfn(mem->phys_index);
> > +       if (is_mem_section_removable(start_pfn, PAGES_PER_SECTION))
> > +               return sprintf(buf, "True\n");
> > +       else
> > +               return sprintf(buf, "False\n");
> > + 
> 
> Yeah, that's what I had in mind.  The only other thing I might suggest
> would be to do a number instead of true/false here.  Just so that we
> _can_ have scores in the future.  Otherwise fine with me.

Good point. Here is the updated version. Thanks for your suggestions.

Thanks,
Badari

Each section of the memory has attributes in /sysfs. This patch adds 
file "removable" to show if this memory block is removable. This
helps user-level agents to identify section of the memory for hotplug 
memory remove.

Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com> 

 drivers/base/memory.c           |   19 +++++++++++++++++++
 include/linux/pageblock-flags.h |    2 ++
 mm/page_alloc.c                 |   27 +++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

Index: linux-2.6.24-rc1/drivers/base/memory.c
===================================================================
--- linux-2.6.24-rc1.orig/drivers/base/memory.c	2007-10-23 20:50:57.000000000 -0700
+++ linux-2.6.24-rc1/drivers/base/memory.c	2007-10-25 18:25:07.000000000 -0700
@@ -105,6 +105,21 @@ static ssize_t show_mem_phys_index(struc
 }
 
 /*
+ * show memory migrate type
+ */
+static ssize_t show_mem_removable(struct sys_device *dev, char *buf)
+{
+	unsigned long start_pfn;
+	int ret;
+	struct memory_block *mem =
+		container_of(dev, struct memory_block, sysdev);
+
+	start_pfn = section_nr_to_pfn(mem->phys_index);
+	ret = is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
+	return sprintf(buf, "%d\n", ret);
+}
+
+/*
  * online, offline, going offline, etc.
  */
 static ssize_t show_mem_state(struct sys_device *dev, char *buf)
@@ -263,6 +278,7 @@ static ssize_t show_phys_device(struct s
 static SYSDEV_ATTR(phys_index, 0444, show_mem_phys_index, NULL);
 static SYSDEV_ATTR(state, 0644, show_mem_state, store_mem_state);
 static SYSDEV_ATTR(phys_device, 0444, show_phys_device, NULL);
+static SYSDEV_ATTR(removable, 0444, show_mem_removable, NULL);
 
 #define mem_create_simple_file(mem, attr_name)	\
 	sysdev_create_file(&mem->sysdev, &attr_##attr_name)
@@ -351,6 +367,8 @@ static int add_memory_block(unsigned lon
 		ret = mem_create_simple_file(mem, state);
 	if (!ret)
 		ret = mem_create_simple_file(mem, phys_device);
+	if (!ret)
+		ret = mem_create_simple_file(mem, removable);
 
 	return ret;
 }
@@ -395,6 +413,7 @@ int remove_memory_block(unsigned long no
 	mem_remove_simple_file(mem, phys_index);
 	mem_remove_simple_file(mem, state);
 	mem_remove_simple_file(mem, phys_device);
+	mem_remove_simple_file(mem, removable);
 	unregister_memory(mem, section, NULL);
 
 	return 0;
Index: linux-2.6.24-rc1/include/linux/pageblock-flags.h
===================================================================
--- linux-2.6.24-rc1.orig/include/linux/pageblock-flags.h	2007-10-23 20:50:57.000000000 -0700
+++ linux-2.6.24-rc1/include/linux/pageblock-flags.h	2007-10-25 17:14:54.000000000 -0700
@@ -67,6 +67,8 @@ unsigned long get_pageblock_flags_group(
 void set_pageblock_flags_group(struct page *page, unsigned long flags,
 					int start_bitidx, int end_bitidx);
 
+int is_mem_section_removable(unsigned long pfn, unsigned long nr_pages);
+
 #define get_pageblock_flags(page) \
 			get_pageblock_flags_group(page, 0, NR_PAGEBLOCK_BITS-1)
 #define set_pageblock_flags(page) \
Index: linux-2.6.24-rc1/mm/page_alloc.c
===================================================================
--- linux-2.6.24-rc1.orig/mm/page_alloc.c	2007-10-23 20:50:57.000000000 -0700
+++ linux-2.6.24-rc1/mm/page_alloc.c	2007-10-25 17:29:30.000000000 -0700
@@ -4489,6 +4489,33 @@ out:
 	spin_unlock_irqrestore(&zone->lock, flags);
 }
 
+/*
+ * Find out if this section of the memory is removable.
+ */
+int
+is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
+{
+	int type, i = 0;
+	struct page *page;
+
+	/*
+	 * Check all pageblocks in the section to ensure they are all
+	 * removable.
+	 */
+	page = pfn_to_page(start_pfn);
+	while (i < nr_pages) {
+		type = get_pageblock_migratetype(page + i);
+
+		/*
+		 * For now, we can remove sections with only MOVABLE pages.
+		 */
+		if (type != MIGRATE_MOVABLE)
+			return 0;
+		i += pageblock_nr_pages;
+	}
+	return 1;
+}
+
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /*
  * All pages in the range must be isolated before calling this.


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