Author: kib
Date: Tue Dec 15 12:58:33 2015
New Revision: 292261
URL: https://svnweb.freebsd.org/changeset/base/292261
Log:
MFC r291576:
Handle invalid pages found during the sleepable collapse scan, do not free
the shadow page swap space. Combine the sleep code.
Modified:
stable/10/sys/vm/vm_object.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/vm/vm_object.c
==============================================================================
--- stable/10/sys/vm/vm_object.c Tue Dec 15 12:52:45 2015
(r292260)
+++ stable/10/sys/vm/vm_object.c Tue Dec 15 12:58:33 2015
(r292261)
@@ -1424,13 +1424,40 @@ retry:
#define OBSC_COLLAPSE_NOWAIT 0x0002
#define OBSC_COLLAPSE_WAIT 0x0004
-static int
+static vm_page_t
+vm_object_backing_scan_wait(vm_object_t object, vm_page_t p, vm_page_t next,
+ int op)
+{
+ vm_object_t backing_object;
+
+ VM_OBJECT_ASSERT_WLOCKED(object);
+ backing_object = object->backing_object;
+ VM_OBJECT_ASSERT_WLOCKED(backing_object);
+
+ KASSERT(p == NULL || vm_page_busied(p), ("unbusy page %p", p));
+ KASSERT(p == NULL || p->object == object || p->object == backing_object,
+ ("invalid ownership %p %p %p", p, object, backing_object));
+ if ((op & OBSC_COLLAPSE_NOWAIT) != 0)
+ return (next);
+ if (p != NULL)
+ vm_page_lock(p);
+ VM_OBJECT_WUNLOCK(object);
+ VM_OBJECT_WUNLOCK(backing_object);
+ if (p == NULL)
+ VM_WAIT;
+ else
+ vm_page_busy_sleep(p, "vmocol");
+ VM_OBJECT_WLOCK(object);
+ VM_OBJECT_WLOCK(backing_object);
+ return (TAILQ_FIRST(&backing_object->memq));
+}
+
+static bool
vm_object_backing_scan(vm_object_t object, int op)
{
- int r = 1;
- vm_page_t p;
vm_object_t backing_object;
- vm_pindex_t backing_offset_index;
+ vm_page_t next, p, pp;
+ vm_pindex_t backing_offset_index, new_pindex;
VM_OBJECT_ASSERT_WLOCKED(object);
VM_OBJECT_ASSERT_WLOCKED(object->backing_object);
@@ -1452,7 +1479,7 @@ vm_object_backing_scan(vm_object_t objec
* shadow test may succeed! XXX
*/
if (backing_object->type != OBJT_DEFAULT) {
- return (0);
+ return (false);
}
}
if (op & OBSC_COLLAPSE_WAIT) {
@@ -1464,24 +1491,19 @@ vm_object_backing_scan(vm_object_t objec
*/
p = TAILQ_FIRST(&backing_object->memq);
while (p) {
- vm_page_t next = TAILQ_NEXT(p, listq);
- vm_pindex_t new_pindex = p->pindex - backing_offset_index;
-
+ next = TAILQ_NEXT(p, listq);
+ new_pindex = p->pindex - backing_offset_index;
if (op & OBSC_TEST_ALL_SHADOWED) {
- vm_page_t pp;
-
/*
* Ignore pages outside the parent object's range
* and outside the parent object's mapping of the
* backing object.
*
- * note that we do not busy the backing object's
+ * Note that we do not busy the backing object's
* page.
*/
- if (
- p->pindex < backing_offset_index ||
- new_pindex >= object->size
- ) {
+ if (p->pindex < backing_offset_index ||
+ new_pindex >= object->size) {
p = next;
continue;
}
@@ -1497,55 +1519,26 @@ vm_object_backing_scan(vm_object_t objec
*/
pp = vm_page_lookup(object, new_pindex);
- if (
- (pp == NULL || pp->valid == 0) &&
- !vm_pager_has_page(object, new_pindex, NULL, NULL)
- ) {
- r = 0;
- break;
- }
+ if ((pp == NULL || pp->valid == 0) &&
+ !vm_pager_has_page(object, new_pindex, NULL, NULL))
+ return (false);
}
/*
* Check for busy page
*/
if (op & (OBSC_COLLAPSE_WAIT | OBSC_COLLAPSE_NOWAIT)) {
- vm_page_t pp;
-
- if (op & OBSC_COLLAPSE_NOWAIT) {
- if (!p->valid || vm_page_busied(p)) {
- p = next;
- continue;
- }
- } else if (op & OBSC_COLLAPSE_WAIT) {
- if (vm_page_busied(p)) {
- VM_OBJECT_WUNLOCK(object);
- vm_page_lock(p);
- VM_OBJECT_WUNLOCK(backing_object);
- vm_page_busy_sleep(p, "vmocol");
- VM_OBJECT_WLOCK(object);
- VM_OBJECT_WLOCK(backing_object);
- /*
- * If we slept, anything could have
- * happened. Since the object is
- * marked dead, the backing offset
- * should not have changed so we
- * just restart our scan.
- */
- p = TAILQ_FIRST(&backing_object->memq);
- continue;
- }
+ if (vm_page_busied(p)) {
+ p = vm_object_backing_scan_wait(object, p,
+ next, op);
+ continue;
}
- KASSERT(
- p->object == backing_object,
- ("vm_object_backing_scan: object mismatch")
- );
-
- if (
- p->pindex < backing_offset_index ||
- new_pindex >= object->size
- ) {
+ KASSERT(p->object == backing_object,
+ ("vm_object_backing_scan: object mismatch"));
+
+ if (p->pindex < backing_offset_index ||
+ new_pindex >= object->size) {
if (backing_object->type == OBJT_SWAP)
swap_pager_freespace(backing_object,
p->pindex, 1);
@@ -1567,43 +1560,45 @@ 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)
- ) {
- if (backing_object->type == OBJT_SWAP)
- swap_pager_freespace(backing_object,
- p->pindex, 1);
-
+ if (pp != NULL && vm_page_busied(pp)) {
/*
- * 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.
+ * The page in the parent is busy and
+ * possibly not (yet) valid. Until
+ * its state is finalized by the busy
+ * bit owner, we can't tell whether it
+ * shadows the original page.
+ * Therefore, we must either skip it
+ * and the original (backing_object)
+ * page or wait for its state to be
+ * finalized.
*
- * 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.
+ * This is due to a race with 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;
+ p = vm_object_backing_scan_wait(object, pp,
+ next, op);
continue;
}
- if (
- pp != NULL ||
- vm_pager_has_page(object, new_pindex, NULL, NULL)
- ) {
- if (backing_object->type == OBJT_SWAP)
- swap_pager_freespace(backing_object,
- p->pindex, 1);
+ KASSERT(pp == NULL || pp->valid != 0,
+ ("unbusy invalid page %p", pp));
+
+ if (pp != NULL || vm_pager_has_page(object,
+ new_pindex, NULL, NULL)) {
/*
- * page already exists in parent OR swap exists
- * for this location in the parent. Destroy
- * the original page from the backing object.
- *
- * Leave the parent's page alone
+ * The page already exists in the
+ * parent OR swap exists for this
+ * location in the parent. Leave the
+ * parent's page alone. Destroy the
+ * original page from the backing
+ * object.
*/
+ if (backing_object->type == OBJT_SWAP)
+ swap_pager_freespace(backing_object,
+ p->pindex, 1);
vm_page_lock(p);
KASSERT(!pmap_page_is_mapped(p),
("freeing mapped page %p", p));
@@ -1625,16 +1620,8 @@ vm_object_backing_scan(vm_object_t objec
* vm_page_rename() will handle dirty and cache.
*/
if (vm_page_rename(p, object, new_pindex)) {
- if (op & OBSC_COLLAPSE_NOWAIT) {
- p = next;
- continue;
- }
- VM_OBJECT_WUNLOCK(backing_object);
- VM_OBJECT_WUNLOCK(object);
- VM_WAIT;
- VM_OBJECT_WLOCK(object);
- VM_OBJECT_WLOCK(backing_object);
- p = TAILQ_FIRST(&backing_object->memq);
+ p = vm_object_backing_scan_wait(object, NULL,
+ next, op);
continue;
}
@@ -1653,7 +1640,7 @@ vm_object_backing_scan(vm_object_t objec
}
p = next;
}
- return (r);
+ return (true);
}
@@ -1820,8 +1807,8 @@ vm_object_collapse(vm_object_t object)
* there is nothing we can do so we give up.
*/
if (object->resident_page_count != object->size &&
- vm_object_backing_scan(object,
- OBSC_TEST_ALL_SHADOWED) == 0) {
+ !vm_object_backing_scan(object,
+ OBSC_TEST_ALL_SHADOWED)) {
VM_OBJECT_WUNLOCK(backing_object);
break;
}
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