WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] [PATCH 2/3 v4] xen-balloon: Add interface to retrieve balloo

To: Ian.Campbell@xxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH 2/3 v4] xen-balloon: Add interface to retrieve ballooned pages
From: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
Date: Tue, 8 Mar 2011 14:49:56 -0500
Cc: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, konrad.wilk@xxxxxxxxxx
Delivery-date: Tue, 08 Mar 2011 11:55:08 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <1299604312.17339.542.camel@xxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <1299604312.17339.542.camel@xxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Pages that have been ballooned are useful for other Xen drivers doing
grant table actions, because these pages have valid struct page/PFNs but
have no valid MFN so are available for remapping.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
 drivers/xen/balloon.c |   65 ++++++++++++++++++++++++++++++++++++++++++++++--
 include/xen/balloon.h |    3 ++
 2 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index b0a7a92..d187fce 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -116,14 +116,17 @@ static void balloon_append(struct page *page)
 }
 
 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
-static struct page *balloon_retrieve(void)
+static struct page *balloon_retrieve(bool prefer_highmem)
 {
        struct page *page;
 
        if (list_empty(&ballooned_pages))
                return NULL;
 
-       page = list_entry(ballooned_pages.next, struct page, lru);
+       if (prefer_highmem)
+               page = list_entry(ballooned_pages.prev, struct page, lru);
+       else
+               page = list_entry(ballooned_pages.next, struct page, lru);
        list_del(&page->lru);
 
        if (PageHighMem(page)) {
@@ -198,7 +201,7 @@ static int increase_reservation(unsigned long nr_pages)
                goto out;
 
        for (i = 0; i < rc; i++) {
-               page = balloon_retrieve();
+               page = balloon_retrieve(0);
                BUG_ON(page == NULL);
 
                pfn = page_to_pfn(page);
@@ -328,6 +331,62 @@ void balloon_set_new_target(unsigned long target)
 }
 EXPORT_SYMBOL_GPL(balloon_set_new_target);
 
+/**
+ * alloc_xenballooned_pages - get pages that have been ballooned out
+ * @nr_pages: Number of pages to get
+ * @pages: pages returned
+ * @return 0 on success, error otherwise
+ */
+int alloc_xenballooned_pages(int nr_pages, struct page** pages)
+{
+       int pgno = 0;
+       struct page* page;
+       mutex_lock(&balloon_mutex);
+       while (pgno < nr_pages) {
+               page = balloon_retrieve(1);
+               if (page) {
+                       pages[pgno++] = page;
+               } else {
+                       if (decrease_reservation(nr_pages - pgno))
+                               goto out_undo;
+               }
+       }
+       mutex_unlock(&balloon_mutex);
+       return 0;
+ out_undo:
+       while (pgno)
+               balloon_append(pages[--pgno]);
+       /* Free the memory back to the kernel soon */
+       schedule_work(&balloon_worker);
+       mutex_unlock(&balloon_mutex);
+       return -ENOMEM;
+}
+EXPORT_SYMBOL(alloc_xenballooned_pages);
+
+/**
+ * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
+ * @nr_pages: Number of pages
+ * @pages: pages to return
+ */
+void free_xenballooned_pages(int nr_pages, struct page** pages)
+{
+       int i;
+
+       mutex_lock(&balloon_mutex);
+
+       for (i = 0; i < nr_pages; i++) {
+               if (pages[i])
+                       balloon_append(pages[i]);
+       }
+
+       /* The balloon may be too large now. Shrink it if needed. */
+       if (current_target() != balloon_stats.current_pages)
+               schedule_work(&balloon_worker);
+
+       mutex_unlock(&balloon_mutex);
+}
+EXPORT_SYMBOL(free_xenballooned_pages);
+
 static int __init balloon_init(void)
 {
        unsigned long pfn, nr_pages, extra_pfn_end;
diff --git a/include/xen/balloon.h b/include/xen/balloon.h
index b2b7c21..72a6927 100644
--- a/include/xen/balloon.h
+++ b/include/xen/balloon.h
@@ -19,3 +19,6 @@ struct balloon_stats {
 extern struct balloon_stats balloon_stats;
 
 void balloon_set_new_target(unsigned long target);
+
+int alloc_xenballooned_pages(int nr_pages, struct page** pages);
+void free_xenballooned_pages(int nr_pages, struct page** pages);
-- 
1.7.3.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel