Re: [PATCH 1/2] Page migration via Swap V2: Page Eviction

Christoph Lameter
2005-10-18T16:38:24Z

On Mon, 17 Oct 2005, Andrew Morton wrote:

> This needs the (uncommented (grr)) smp_rmb() copied-and-pasted as well.
>
> It's a shame about the copy-and-pasting :( Is it unavoidable?

Well there is a way at least to extract a major section from it that
includes the smb_rmb().

Index: linux-2.6.14-rc4-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.14-rc4-mm1.orig/mm/vmscan.c 2005-10-18 09:36:36.000000000 -0700
+++ linux-2.6.14-rc4-mm1/mm/vmscan.c 2005-10-18 09:36:42.000000000 -0700
@@ -370,6 +370,42 @@ static pageout_t pageout(struct page *pa
return PAGE_CLEAN;
}

+static inline int remove_mapping(struct address_space *mapping,
+ struct page *page)
+{
+ if (!mapping)
+ return 0; /* truncate got there first */
+
+ write_lock_irq(&mapping->tree_lock);
+
+ /*
+ * The non-racy check for busy page. It is critical to check
+ * PageDirty _after_ making sure that the page is freeable and
+ * not in use by anybody. (pagecache + us == 2)
+ */
+ if (page_count(page) != 2 || PageDirty(page)) {
+ write_unlock_irq(&mapping->tree_lock);
+ return 0;
+ }
+
+#ifdef CONFIG_SWAP
+ if (PageSwapCache(page)) {
+ swp_entry_t swap = { .val = page->private };
+ add_to_swapped_list(swap.val);
+ __delete_from_swap_cache(page);
+ write_unlock_irq(&mapping->tree_lock);
+ swap_free(swap);
+ __put_page(page); /* The pagecache ref */
+ return 1;
+ }
+#endif /* CONFIG_SWAP */
+
+ __remove_from_page_cache(page);
+ write_unlock_irq(&mapping->tree_lock);
+ __put_page(page);
+ return 1;
+}
+
/*
* shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
*/
@@ -508,36 +544,8 @@ static int shrink_list(struct list_head
goto free_it;
}

- if (!mapping)
- goto keep_locked; /* truncate got there first */
-
- write_lock_irq(&mapping->tree_lock);
-
- /*
- * The non-racy check for busy page. It is critical to check
- * PageDirty _after_ making sure that the page is freeable and
- * not in use by anybody. (pagecache + us == 2)
- */
- if (page_count(page) != 2 || PageDirty(page)) {
- write_unlock_irq(&mapping->tree_lock);
+ if (!remove_mapping(mapping, page))
goto keep_locked;
- }
-
-#ifdef CONFIG_SWAP
- if (PageSwapCache(page)) {
- swp_entry_t swap = { .val = page->private };
- add_to_swapped_list(swap.val);
- __delete_from_swap_cache(page);
- write_unlock_irq(&mapping->tree_lock);
- swap_free(swap);
- __put_page(page); /* The pagecache ref */
- goto free_it;
- }
-#endif /* CONFIG_SWAP */
-
- __remove_from_page_cache(page);
- write_unlock_irq(&mapping->tree_lock);
- __put_page(page);

free_it:
unlock_page(page);
@@ -646,31 +654,9 @@ redo:
goto free_it;
}

- if (!mapping)
+ if (!remove_mapping(mapping, page))
goto retry_later_locked; /* truncate got there first */

- write_lock_irq(&mapping->tree_lock);
-
- if (page_count(page) != 2 || PageDirty(page)) {
- write_unlock_irq(&mapping->tree_lock);
- goto retry_later_locked;
- }
-
-#ifdef CONFIG_SWAP
- if (PageSwapCache(page)) {
- swp_entry_t swap = { .val = page->private };
- __delete_from_swap_cache(page);
- write_unlock_irq(&mapping->tree_lock);
- swap_free(swap);
- __put_page(page); /* The pagecache ref */
- goto free_it;
- }
-#endif /* CONFIG_SWAP */
-
- __remove_from_page_cache(page);
- write_unlock_irq(&mapping->tree_lock);
- __put_page(page);
-
free_it:
/*
* We may free pages that were taken off the active list