Author: kib
Date: Wed Sep 11 04:55:10 2019
New Revision: 352202
URL: https://svnweb.freebsd.org/changeset/base/352202
Log:
MFC r351830:
madvise(MADV_FREE): Quick fix to time rewind.
PR: 240061
Modified:
stable/12/sys/vm/vm_map.c
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/vm/vm_map.c
==============================================================================
--- stable/12/sys/vm/vm_map.c Wed Sep 11 03:25:30 2019 (r352201)
+++ stable/12/sys/vm/vm_map.c Wed Sep 11 04:55:10 2019 (r352202)
@@ -2735,6 +2735,18 @@ vm_map_madvise(
if (current->eflags & MAP_ENTRY_IS_SUB_MAP)
continue;
+ /*
+ * MADV_FREE would otherwise rewind time to
+ * the creation of the shadow object. Because
+ * we hold the VM map read-locked, neither the
+ * entry's object nor the presence of a
+ * backing object can change.
+ */
+ if (behav == MADV_FREE &&
+ current->object.vm_object != NULL &&
+ current->object.vm_object->backing_object != NULL)
+ continue;
+
pstart = OFF_TO_IDX(current->offset);
pend = pstart + atop(current->end - current->start);
useStart = current->start;
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