svn commit: r365437 - head/sys/vm
Mark Johnston
markj at FreeBSD.org
Mon Sep 7 23:28:33 UTC 2020
Author: markj
Date: Mon Sep 7 23:28:33 2020
New Revision: 365437
URL: https://svnweb.freebsd.org/changeset/base/365437
Log:
vm_object_split(): Handle orig_object type changes.
orig_object->type can change from OBJT_DEFAULT to OBJT_SWAP while
vm_object_split() is sleeping. In this case some pages in new_object
may be left unbusied, but vm_object_split() attempts to unbusy all of
them.
Track the beginning of the busied range. Add an assertion to verify
that pages are not re-added to the source object while sleeping.
Reported by: Olympios Petrakis <olympios.petrakis at netapp.com>
Reviewed by: alc, kib
Tested by: pho
MFC after: 1 week
Sponsored by: NetApp, Inc.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D26223
Modified:
head/sys/vm/vm_object.c
Modified: head/sys/vm/vm_object.c
==============================================================================
--- head/sys/vm/vm_object.c Mon Sep 7 23:22:16 2020 (r365436)
+++ head/sys/vm/vm_object.c Mon Sep 7 23:28:33 2020 (r365437)
@@ -1496,7 +1496,7 @@ vm_object_shadow(vm_object_t *object, vm_ooffset_t *of
void
vm_object_split(vm_map_entry_t entry)
{
- vm_page_t m, m_next;
+ vm_page_t m, m_busy, m_next;
vm_object_t orig_object, new_object, backing_object;
vm_pindex_t idx, offidxstart;
vm_size_t size;
@@ -1553,8 +1553,14 @@ vm_object_split(vm_map_entry_t entry)
* that the object is in transition.
*/
vm_object_set_flag(orig_object, OBJ_SPLIT);
+ m_busy = NULL;
+#ifdef INVARIANTS
+ idx = 0;
+#endif
retry:
m = vm_page_find_least(orig_object, offidxstart);
+ KASSERT(m == NULL || idx <= m->pindex - offidxstart,
+ ("%s: object %p was repopulated", __func__, orig_object));
for (; m != NULL && (idx = m->pindex - offidxstart) < size;
m = m_next) {
m_next = TAILQ_NEXT(m, listq);
@@ -1609,8 +1615,15 @@ retry:
*/
vm_reserv_rename(m, new_object, orig_object, offidxstart);
#endif
+
+ /*
+ * orig_object's type may change while sleeping, so keep track
+ * of the beginning of the busied range.
+ */
if (orig_object->type != OBJT_SWAP)
vm_page_xunbusy(m);
+ else if (m_busy == NULL)
+ m_busy = m;
}
if (orig_object->type == OBJT_SWAP) {
/*
@@ -1618,8 +1631,9 @@ retry:
* and new_object's locks are released and reacquired.
*/
swap_pager_copy(orig_object, new_object, offidxstart, 0);
- TAILQ_FOREACH(m, &new_object->memq, listq)
- vm_page_xunbusy(m);
+ if (m_busy != NULL)
+ TAILQ_FOREACH_FROM(m_busy, &new_object->memq, listq)
+ vm_page_xunbusy(m_busy);
}
vm_object_clear_flag(orig_object, OBJ_SPLIT);
VM_OBJECT_WUNLOCK(orig_object);
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