From 1f348a695fa0a22ee1e99c8972181de859ec3d87 Mon Sep 17 00:00:00 2001 From: Andres Lagar-Cavilla Date: Thu, 5 Apr 2012 11:06:03 +0100 Subject: [PATCH] x86/mm: Take care of domain reference for shared pages Making a page sharable removes it from the previous owner's list. Making it private adds it. These actions are similar to freeing or allocating a page. Except that they were not minding the domain reference that is taken/dropped when the first/last page is allocated/freed. Without fixing this, a domain might remain zombie when destroyed if all its pages are shared. Signed-off-by: Andres Lagar-Cavilla Acked-by: Tim Deegan Committed-by: Tim Deegan --- xen/arch/x86/mm/mem_sharing.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c index c838fd848f..11c4ff62e5 100644 --- a/xen/arch/x86/mm/mem_sharing.c +++ b/xen/arch/x86/mm/mem_sharing.c @@ -401,6 +401,7 @@ static int page_make_sharable(struct domain *d, struct page_info *page, int expected_refcnt) { + int drop_dom_ref; spin_lock(&d->page_alloc_lock); /* Change page type and count atomically */ @@ -430,8 +431,12 @@ static int page_make_sharable(struct domain *d, page_set_owner(page, dom_cow); d->tot_pages--; + drop_dom_ref = (d->tot_pages == 0); page_list_del(page, &d->page_list); spin_unlock(&d->page_alloc_lock); + + if ( drop_dom_ref ) + put_domain(d); return 0; } @@ -466,7 +471,8 @@ static int page_make_private(struct domain *d, struct page_info *page) ASSERT(page_get_owner(page) == dom_cow); page_set_owner(page, d); - d->tot_pages++; + if ( d->tot_pages++ == 0 ) + get_domain(d); page_list_add_tail(page, &d->page_list); spin_unlock(&d->page_alloc_lock); -- 2.30.2