hotplug memory remove: generic __remove_pages() support

Generic helper function to remove section mappings and sysfs entries for the
section of the memory we are removing.  offline_pages() correctly adjusted
zone and marked the pages reserved.

TODO: Yasunori Goto is working on patches to free up allocations from bootmem.

Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Acked-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 42 insertions, 3 deletions

diff --git a/mm/sparse.c b/mm/sparse.c
index 7e9191381f86..186a85bf7912 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -208,12 +208,13 @@ static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long p
 }
 
 /*
- * We need this if we ever free the mem_maps.  While not implemented yet,
- * this function is included for parity with its sibling.
+ * Decode mem_map from the coded memmap
  */
-static __attribute((unused))
+static
 struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum)
 {
+        /* mask off the extra low bits of information */
+        coded_mem_map &= SECTION_MAP_MASK;
         return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum);
 }
 
@@ -404,6 +405,28 @@ static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
+static void free_section_usemap(struct page *memmap, unsigned long *usemap)
+{
+        if (!usemap)
+                return;
+
+        /*
+         * Check to see if allocation came from hot-plug-add
+         */
+        if (PageSlab(virt_to_page(usemap))) {
+                kfree(usemap);
+                if (memmap)
+                        __kfree_section_memmap(memmap, PAGES_PER_SECTION);
+                return;
+        }
+
+        /*
+         * TODO: Allocations came from bootmem - how do I free up ?
+         */
+        printk(KERN_WARNING "Not freeing up allocations from bootmem "
+                        "- leaking memory\n");
+}
+
 /*
  * returns the number of sections whose mem_maps were properly
  * set.  If this is <=0, then that means that the passed-in
@@ -456,4 +479,20 @@ out:
         }
         return ret;
 }
+
+void sparse_remove_one_section(struct zone *zone, struct mem_section *ms)
+{
+        struct page *memmap = NULL;
+        unsigned long *usemap = NULL;
+
+        if (ms->section_mem_map) {
+                usemap = ms->pageblock_flags;
+                memmap = sparse_decode_mem_map(ms->section_mem_map,
+                                                __section_nr(ms));
+                ms->section_mem_map = 0;
+                ms->pageblock_flags = NULL;
+        }
+
+        free_section_usemap(memmap, usemap);
+}
 #endif