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diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -348,13 +348,38 @@
MPASS(fs->vp == NULL);
+ /*
+ * If we fail, vast majority of the time it is because the page is not
+ * there to begin with. Opportunistically perform the lookup and
+ * subsequent checks without the object lock, revalidate later.
+ *
+ * Note: a busy page can be mapped for read|execute access.
+ */
+ m = vm_page_lookup_unlocked(fs->first_object, fs->first_pindex);
+ if (m == NULL || !vm_page_all_valid(m) ||
+ ((fs->prot & VM_PROT_WRITE) != 0 && vm_page_busied(m))) {
+ VM_OBJECT_WLOCK(fs->first_object);
+ return (FAULT_FAILURE);
+ }
+
vaddr = fs->vaddr;
- vm_object_busy(fs->first_object);
- m = vm_page_lookup(fs->first_object, fs->first_pindex);
- /* A busy page can be mapped for read|execute access. */
- if (m == NULL || ((fs->prot & VM_PROT_WRITE) != 0 &&
- vm_page_busied(m)) || !vm_page_all_valid(m))
+
+ VM_OBJECT_RLOCK(fs->first_object);
+
+ /*
+ * Now that we stabilized the state, revalidate the page is in the shape
+ * we encountered above.
+ */
+
+ if (m->object != fs->first_object || m->pindex != fs->first_pindex)
goto fail;
+
+ vm_object_busy(fs->first_object);
+
+ if (!vm_page_all_valid(m) ||
+ ((fs->prot & VM_PROT_WRITE) != 0 && vm_page_busied(m)))
+ goto fail_busy;
+
m_map = m;
psind = 0;
#if VM_NRESERVLEVEL > 0
@@ -390,7 +415,7 @@
if (pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type |
PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind) !=
KERN_SUCCESS)
- goto fail;
+ goto fail_busy;
if (fs->m_hold != NULL) {
(*fs->m_hold) = m;
vm_page_wire(m);
@@ -403,8 +428,13 @@
vm_map_lookup_done(fs->map, fs->entry);
curthread->td_ru.ru_minflt++;
return (FAULT_SUCCESS);
-fail:
+fail_busy:
vm_object_unbusy(fs->first_object);
+fail:
+ if (!VM_OBJECT_TRYUPGRADE(fs->first_object)) {
+ VM_OBJECT_RUNLOCK(fs->first_object);
+ VM_OBJECT_WLOCK(fs->first_object);
+ }
return (FAULT_FAILURE);
}
@@ -1556,14 +1586,12 @@
if (fs.vp == NULL /* avoid locked vnode leak */ &&
(fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) == 0 &&
(fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) {
- VM_OBJECT_RLOCK(fs.first_object);
res = vm_fault_soft_fast(&fs);
- if (res == FAULT_SUCCESS)
+ if (res == FAULT_SUCCESS) {
+ VM_OBJECT_ASSERT_UNLOCKED(fs.first_object);
return (KERN_SUCCESS);
- if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
- VM_OBJECT_RUNLOCK(fs.first_object);
- VM_OBJECT_WLOCK(fs.first_object);
}
+ VM_OBJECT_ASSERT_WLOCKED(fs.first_object);
} else {
VM_OBJECT_WLOCK(fs.first_object);
}

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