[PATCH] memory hotplug locking: node_size_lock

pgdat->node_size_lock is basically only neeeded in one place in the normal
code: show_mem(), which is the arch-specific sysrq-m printing function.

Strictly speaking, the architectures not doing memory hotplug do no need this
locking in show_mem().  However, they are all included for completeness.  This
should also make any future consolidation of all of the implementations a
little more straightforward.

This lock is also held in the sparsemem code during a memory removal, as
sections are invalidated.  This is the place there pfn_valid() is made false
for a memory area that's being removed.  The lock is only required when doing
pfn_valid() operations on memory which the user does not already have a
reference on the page, such as in show_mem().

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/ppc64/mm/init.c b/arch/ppc64/mm/init.c
index a45584b3440c..975b26de34d6 100644
--- a/arch/ppc64/mm/init.c
+++ b/arch/ppc64/mm/init.c
@@ -104,6 +104,8 @@ void show_mem(void)
         show_free_areas();
         printk("Free swap:       %6ldkB\n", nr_swap_pages<<(PAGE_SHIFT-10));
         for_each_pgdat(pgdat) {
+                unsigned long flags;
+                pgdat_resize_lock(pgdat, &flags);
                 for (i = 0; i < pgdat->node_spanned_pages; i++) {
                         page = pgdat_page_nr(pgdat, i);
                         total++;
@@ -114,6 +116,7 @@ void show_mem(void)
                         else if (page_count(page))
                                 shared += page_count(page) - 1;
                 }
+                pgdat_resize_unlock(pgdat, &flags);
         }
         printk("%ld pages of RAM\n", total);
         printk("%ld reserved pages\n", reserved);
@@ -647,11 +650,14 @@ void __init mem_init(void)
 #endif
 
         for_each_pgdat(pgdat) {
+                unsigned long flags;
+                pgdat_resize_lock(pgdat, &flags);
                 for (i = 0; i < pgdat->node_spanned_pages; i++) {
                         page = pgdat_page_nr(pgdat, i);
                         if (PageReserved(page))
                                 reservedpages++;
                 }
+                pgdat_resize_unlock(pgdat, &flags);
         }
 
         codesize = (unsigned long)&_etext - (unsigned long)&_stext;