Page host virtual assist: volatile swap cache.

diff -urpN linux-2.6/include/linux/pagemap.h linux-2.6-patched/include/linux/pagemap.h
@@ -81,6 +81,13 @@ unsigned find_get_pages(struct address_s
 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
 			int tag, unsigned int nr_pages, struct page **pages);
 
+#if defined(CONFIG_PAGE_HVA)
+extern struct page * find_get_page_nohv(struct address_space *mapping,
+				unsigned long index);
+#else
+#define find_get_page_nohv(mapping, index)	find_get_page(mapping, index)
+#endif
+
 /*
  * Returns locked page at given index in given cache, creating it if needed.
  */

diff -urpN linux-2.6/mm/filemap.c linux-2.6-patched/mm/filemap.c
@@ -574,6 +574,25 @@ struct page * find_get_page(struct addre
 
 EXPORT_SYMBOL(find_get_page);
 
+#if defined(CONFIG_PAGE_HVA)
+
+struct page * find_get_page_nohv(struct address_space *mapping,
+				unsigned long offset)
+{
+	struct page *page;
+
+	read_lock_irq(&mapping->tree_lock);
+	page = radix_tree_lookup(&mapping->page_tree, offset);
+	if (page)
+		page_cache_get(page);
+	read_unlock_irq(&mapping->tree_lock);
+	return page;
+}
+
+EXPORT_SYMBOL(find_get_page_nohv);
+
+#endif
+
 /*
  * Same as above, but trylock it instead of incrementing the count.
  */

diff -urpN linux-2.6/mm/memory.c linux-2.6-patched/mm/memory.c
@@ -1967,8 +1967,16 @@ static int do_swap_page(struct mm_struct
 	unlock_page(page);
 
 	if (write_access) {
-		if (do_wp_page(mm, vma, address,
-				page_table, pmd, ptl, pte) == VM_FAULT_OOM)
+		int rc = do_wp_page(mm, vma, address, page_table,
+				    pmd, ptl, pte);
+		if (page_hva_enabled() && rc == VM_FAULT_MAJOR)
+			/*
+			 * A discard removed the page, and do_wp_page called
+			 * page_hva_discard_page which removed the pte as well.
+			 * handle_pte_fault needs to be repeated.
+			 */
+			ret = VM_FAULT_MINOR;
+		else if (rc == VM_FAULT_OOM)
 			ret = VM_FAULT_OOM;
 		goto out;
 	}

diff -urpN linux-2.6/mm/page_hva.c linux-2.6-patched/mm/page_hva.c
@@ -17,6 +17,7 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/buffer_head.h>
+#include <linux/swap.h>
 
 #include "internal.h"
 

@@ -32,7 +33,7 @@ static inline int __page_hva_discardable
 	 */
 	if (PageDirty(page) || PageReserved(page) || PageWriteback(page) ||
 	    PageLocked(page) || PagePrivate(page) || PageDiscarded(page) ||
-	    !PageUptodate(page) || PageAnon(page))
+	    !PageUptodate(page) || (PageAnon(page) && !PageSwapCache(page)))
 		return 0;
 
 	/*

@@ -149,11 +150,11 @@ static void __page_hva_discard_page(stru
 	del_page_from_lru(zone, page);
 	spin_unlock_irq(&zone->lru_lock);
 
-	/* We can't handle swap cache pages (yet). */
-	BUG_ON(PageSwapCache(page));
-
-	/* Remove page from page cache. */
-	remove_from_page_cache(page);
+	/* Remove page from page/swap cache. */
+	if (PageSwapCache(page))
+		delete_from_swap_cache(page);
+	else
+		remove_from_page_cache(page);
 }
 
 /**

76 lines not on this page · raw message

diff -urpN linux-2.6/mm/swapfile.c linux-2.6-patched/mm/swapfile.c
@@ -401,7 +401,12 @@ void free_swap_and_cache(swp_entry_t ent
 	p = swap_info_get(entry);
 	if (p) {
 		if (swap_entry_free(p, swp_offset(entry)) == 1) {
-			page = find_get_page(&swapper_space, entry.val);
+			/*
+			 * Use find_get_page_nohv to avoid the deadlock
+			 * on the swap_lock and the page table lock if
+			 * the page has been discarded.
+			 */
+			page = find_get_page_nohv(&swapper_space, entry.val);
 			if (page && unlikely(TestSetPageLocked(page))) {
 				page_cache_release(page);
 				page = NULL;

@@ -418,8 +423,17 @@ void free_swap_and_cache(swp_entry_t ent
 		/* Also recheck PageSwapCache after page is locked (above) */
 		if (PageSwapCache(page) && !PageWriteback(page) &&
 					(one_user || vm_swap_full())) {
-			delete_from_swap_cache(page);
-			SetPageDirty(page);
+			/*
+			 * The caller of free_swap_and_cache holds a
+			 * page table lock for this page. A discarded
+			 * page can not be removed at this point. To be
+			 * able to reload the page from swap the swap
+			 * slot may not be freed.
+			 */
+			if (likely(page_hva_make_stable(page))) {
+				delete_from_swap_cache(page);
+				SetPageDirty(page);
+			}
 		}
 		unlock_page(page);
 		page_cache_release(page);