[PATCH] Fix NULL pointer dereference in node_read_numastat()
[linux-2.6.git] / mm / swap_state.c
index a063a90..e0e1583 100644 (file)
@@ -14,6 +14,8 @@
 #include <linux/pagemap.h>
 #include <linux/buffer_head.h>
 #include <linux/backing-dev.h>
+#include <linux/pagevec.h>
+#include <linux/migrate.h>
 
 #include <asm/pgtable.h>
 
@@ -26,6 +28,7 @@ static struct address_space_operations swap_aops = {
        .writepage      = swap_writepage,
        .sync_page      = block_sync_page,
        .set_page_dirty = __set_page_dirty_nobuffers,
+       .migratepage    = migrate_page,
 };
 
 static struct backing_dev_info swap_backing_dev_info = {
@@ -40,7 +43,6 @@ struct address_space swapper_space = {
        .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
        .backing_dev_info = &swap_backing_dev_info,
 };
-EXPORT_SYMBOL(swapper_space);
 
 #define INC_CACHE_INFO(x)      do { swap_cache_info.x++; } while (0)
 
@@ -67,8 +69,8 @@ void show_swap_cache_info(void)
  * __add_to_swap_cache resembles add_to_page_cache on swapper_space,
  * but sets SwapCache flag and private instead of mapping and index.
  */
-static int __add_to_swap_cache(struct page *page,
-               swp_entry_t entry, int gfp_mask)
+static int __add_to_swap_cache(struct page *page, swp_entry_t entry,
+                              gfp_t gfp_mask)
 {
        int error;
 
@@ -83,7 +85,7 @@ static int __add_to_swap_cache(struct page *page,
                        page_cache_get(page);
                        SetPageLocked(page);
                        SetPageSwapCache(page);
-                       page->private = entry.val;
+                       set_page_private(page, entry.val);
                        total_swapcache_pages++;
                        pagecache_acct(1);
                }
@@ -124,9 +126,10 @@ void __delete_from_swap_cache(struct page *page)
        BUG_ON(!PageLocked(page));
        BUG_ON(!PageSwapCache(page));
        BUG_ON(PageWriteback(page));
+       BUG_ON(PagePrivate(page));
 
-       radix_tree_delete(&swapper_space.page_tree, page->private);
-       page->private = 0;
+       radix_tree_delete(&swapper_space.page_tree, page_private(page));
+       set_page_private(page, 0);
        ClearPageSwapCache(page);
        total_swapcache_pages--;
        pagecache_acct(-1);
@@ -140,43 +143,31 @@ void __delete_from_swap_cache(struct page *page)
  * Allocate swap space for the page and add the page to the
  * swap cache.  Caller needs to hold the page lock. 
  */
-int add_to_swap(struct page * page)
+int add_to_swap(struct page * page, gfp_t gfp_mask)
 {
        swp_entry_t entry;
-       int pf_flags;
        int err;
 
-       if (!PageLocked(page))
-               BUG();
+       BUG_ON(!PageLocked(page));
 
        for (;;) {
                entry = get_swap_page();
                if (!entry.val)
                        return 0;
 
-               /* Radix-tree node allocations are performing
-                * GFP_ATOMIC allocations under PF_MEMALLOC.  
-                * They can completely exhaust the page allocator.  
-                *
-                * So PF_MEMALLOC is dropped here.  This causes the slab 
-                * allocations to fail earlier, so radix-tree nodes will 
-                * then be allocated from the mempool reserves.
+               /*
+                * Radix-tree node allocations from PF_MEMALLOC contexts could
+                * completely exhaust the page allocator. __GFP_NOMEMALLOC
+                * stops emergency reserves from being allocated.
                 *
-                * We're still using __GFP_HIGH for radix-tree node
-                * allocations, so some of the emergency pools are available,
-                * just not all of them.
+                * TODO: this could cause a theoretical memory reclaim
+                * deadlock in the swap out path.
                 */
-
-               pf_flags = current->flags;
-               current->flags &= ~PF_MEMALLOC;
-
                /*
                 * Add it to the swap cache and mark it dirty
                 */
-               err = __add_to_swap_cache(page, entry, GFP_ATOMIC|__GFP_NOWARN);
-
-               if (pf_flags & PF_MEMALLOC)
-                       current->flags |= PF_MEMALLOC;
+               err = __add_to_swap_cache(page, entry,
+                               gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN);
 
                switch (err) {
                case 0:                         /* Success */
@@ -207,12 +198,7 @@ void delete_from_swap_cache(struct page *page)
 {
        swp_entry_t entry;
 
-       BUG_ON(!PageSwapCache(page));
-       BUG_ON(!PageLocked(page));
-       BUG_ON(PageWriteback(page));
-       BUG_ON(PagePrivate(page));
-  
-       entry.val = page->private;
+       entry.val = page_private(page);
 
        write_lock_irq(&swapper_space.tree_lock);
        __delete_from_swap_cache(page);
@@ -274,8 +260,7 @@ static inline void free_swap_cache(struct page *page)
 
 /* 
  * Perform a free_page(), also freeing any swap cache associated with
- * this page if it is the last user of the page. Can not do a lock_page,
- * as we are holding the page_table_lock spinlock.
+ * this page if it is the last user of the page.
  */
 void free_page_and_swap_cache(struct page *page)
 {
@@ -289,12 +274,11 @@ void free_page_and_swap_cache(struct page *page)
  */
 void free_pages_and_swap_cache(struct page **pages, int nr)
 {
-       int chunk = 16;
        struct page **pagep = pages;
 
        lru_add_drain();
        while (nr) {
-               int todo = min(chunk, nr);
+               int todo = min(nr, PAGEVEC_SIZE);
                int i;
 
                for (i = 0; i < todo; i++)