Author: mlaier
Date: Mon May 9 20:27:49 2011
New Revision: 221714
URL: http://svn.freebsd.org/changeset/base/221714
Log:
Another long standing vm bug found at Isilon:
Fix a race between vm_object_collapse and vm_fault.
Reviewed by: alc@
MFC after: 3 days
Modified:
head/sys/vm/vm_object.c
Modified: head/sys/vm/vm_object.c
==============================================================================
--- head/sys/vm/vm_object.c Mon May 9 20:20:43 2011 (r221713)
+++ head/sys/vm/vm_object.c Mon May 9 20:27:49 2011 (r221714)
@@ -1468,6 +1468,24 @@ vm_object_backing_scan(vm_object_t objec
pp = vm_page_lookup(object, new_pindex);
if (
+ (op & OBSC_COLLAPSE_NOWAIT) != 0 &&
+ (pp != NULL && pp->valid == 0)
+ ) {
+ /*
+ * The page in the parent is not (yet) valid.
+ * We don't know anything about the state of
+ * the original page. It might be mapped,
+ * so we must avoid the next if here.
+ *
+ * This is due to a race in vm_fault() where
+ * we must unbusy the original (backing_obj)
+ * page before we can (re)lock the parent.
+ * Hence we can get here.
+ */
+ p = next;
+ continue;
+ }
+ if (
pp != NULL ||
vm_pager_has_page(object, new_pindex, NULL, NULL)
) {
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