[Xen-devel] [PATCH] xen/mm: Avoid assuming PG_state_inuse == 0 in assign_pages()

From: Julien Grall <julien@xen.org>
To: xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Julien Grall <julien@xen.org>, Wei Liu <wl@xen.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Julien Grall <jgrall@amazon.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	Jan Beulich <jbeulich@suse.com>
Subject: [Xen-devel] [PATCH] xen/mm: Avoid assuming PG_state_inuse == 0 in assign_pages()
Date: Tue,  4 Feb 2020 13:33:57 +0000	[thread overview]
Message-ID: <20200204133357.32101-1-julien@xen.org> (raw)

From: Julien Grall <jgrall@amazon.com>

At the moment, assign_pages() relies on PG_state_inuse to be 0. This
makes the code slightly more difficult to understand.

Rework the code to explicitly check against PG_state_inuse.

Signed-off-by: Julien Grall <jgrall@amazon.com>
---
 xen/common/page_alloc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 97902d42c1..54773bc42f 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2286,10 +2286,11 @@ int assign_pages(
     for ( i = 0; i < (1 << order); i++ )
     {
         ASSERT(page_get_owner(&pg[i]) == NULL);
-        ASSERT(!pg[i].count_info);
+        ASSERT(page_state_is(&pg[i], inuse));
+        ASSERT(!(pg[i].count_info & (~PGC_state)));
         page_set_owner(&pg[i], d);
         smp_wmb(); /* Domain pointer must be visible before updating refcnt. */
-        pg[i].count_info = PGC_allocated | 1;
+        pg[i].count_info = PGC_state_inuse | PGC_allocated | 1;
         page_list_add_tail(&pg[i], &d->page_list);
     }
 
-- 
2.17.1


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