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Complete the vm object locking in vm_object_backing_scan(); specifically,

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deal with the case where we need to sleep on a busy page with two vm object
locks held.
This commit is contained in:
Alan Cox 2003-06-22 02:35:06 +00:00
parent e3ee6a27a9
commit 7ca33ad1e8
1 changed files with 12 additions and 5 deletions
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17
sys/vm/vm_object.c
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@ -1272,7 +1272,8 @@ vm_object_backing_scan(vm_object_t object, int op)
vm_pindex_t backing_offset_index;
s = splvm();
GIANT_REQUIRED;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
VM_OBJECT_LOCK_ASSERT(object->backing_object, MA_OWNED);
backing_object = object->backing_object;
backing_offset_index = OFF_TO_IDX(object->backing_object_offset);
@ -1364,7 +1365,15 @@ vm_object_backing_scan(vm_object_t object, int op)
continue;
}
} else if (op & OBSC_COLLAPSE_WAIT) {
if (vm_page_sleep_if_busy(p, TRUE, "vmocol")) {
if ((p->flags & PG_BUSY) || p->busy) {
vm_page_flag_set(p,
PG_WANTED | PG_REFERENCED);
VM_OBJECT_UNLOCK(backing_object);
VM_OBJECT_UNLOCK(object);
msleep(p, &vm_page_queue_mtx,
PDROP | PVM, "vmocol", 0);
VM_OBJECT_LOCK(object);
VM_OBJECT_LOCK(backing_object);
/*
* If we slept, anything could have
* happened. Since the object is
@ -1536,7 +1545,6 @@ vm_object_collapse(vm_object_t object)
* case.
*/
if (backing_object->ref_count == 1) {
/* XXX */ VM_OBJECT_UNLOCK(object);
/*
* If there is exactly one reference to the backing
* object, we can collapse it into the parent.
@ -1557,7 +1565,6 @@ vm_object_collapse(vm_object_t object)
* new swapper is able to optimize the
* destroy-source case.
*/
VM_OBJECT_LOCK(object);
vm_object_pip_add(object, 1);
VM_OBJECT_UNLOCK(object);
swap_pager_copy(
@ -1566,7 +1573,6 @@ vm_object_collapse(vm_object_t object)
OFF_TO_IDX(object->backing_object_offset), TRUE);
VM_OBJECT_LOCK(object);
vm_object_pip_wakeup(object);
VM_OBJECT_UNLOCK(object);
VM_OBJECT_LOCK(backing_object);
vm_object_pip_wakeup(backing_object);
@ -1602,6 +1608,7 @@ vm_object_collapse(vm_object_t object)
object->backing_object_offset +=
backing_object->backing_object_offset;
/* XXX */ VM_OBJECT_UNLOCK(object);
/*
* Discard backing_object.