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Index: sys/vm/vm_fault.c
===================================================================
--- sys/vm/vm_fault.c
+++ sys/vm/vm_fault.c
@@ -1047,11 +1047,74 @@
curthread->td_cow++;
}
+enum object_locked { UNLOCKED, RLOCK, WLOCK };
+
+static void
+vm_fault_object_unlock(struct faultstate *fs, enum object_locked objlocked)
+{
+
+ switch (objlocked) {
+ case RLOCK:
+ VM_OBJECT_RUNLOCK(fs->object);
+ return;
+ case WLOCK:
+ VM_OBJECT_WUNLOCK(fs->object);
+ return;
+ case UNLOCKED:
+ panic("object %p already unlocked", fs->object);
+ }
+
+ __assert_unreachable();
+}
+
+static bool
+vm_fault_object_upgrade_cond(struct faultstate *fs, enum object_locked *objlocked)
+{
+
+ switch (*objlocked) {
+ case WLOCK:
+ VM_OBJECT_ASSERT_WLOCKED(fs->object);
+ return (true);
+ case RLOCK:
+ *objlocked = WLOCK;
+ if (VM_OBJECT_TRYUPGRADE(fs->object))
+ return (true);
+
+ VM_OBJECT_RUNLOCK(fs->object);
+ VM_OBJECT_WLOCK(fs->object);
+ return (false);
+ case UNLOCKED:
+ panic("object %p not locked", fs->object);
+ }
+
+ __assert_unreachable();
+}
+
+static void
+vm_fault_object_lock_assert(struct faultstate *fs, enum object_locked objlocked)
+{
+
+ switch (objlocked) {
+ case WLOCK:
+ VM_OBJECT_ASSERT_WLOCKED(fs->object);
+ return;
+ case RLOCK:
+ VM_OBJECT_ASSERT_RLOCKED(fs->object);
+ return;
+ case UNLOCKED:
+ panic("object %p not locked", fs->object);
+ }
+
+ __assert_unreachable();
+}
+
static bool
-vm_fault_next(struct faultstate *fs)
+vm_fault_next(struct faultstate *fs, enum object_locked *objlocked)
{
vm_object_t next_object;
+ vm_fault_object_lock_assert(fs, *objlocked);
+
/*
* The requested page does not exist at this object/
* offset. Remove the invalid page from the object,
@@ -1072,19 +1135,19 @@
* Move on to the next object. Lock the next object before
* unlocking the current one.
*/
- VM_OBJECT_ASSERT_WLOCKED(fs->object);
next_object = fs->object->backing_object;
if (next_object == NULL)
return (false);
MPASS(fs->first_m != NULL);
KASSERT(fs->object != next_object, ("object loop %p", next_object));
- VM_OBJECT_WLOCK(next_object);
+ VM_OBJECT_RLOCK(next_object);
vm_object_pip_add(next_object, 1);
if (fs->object != fs->first_object)
vm_object_pip_wakeup(fs->object);
fs->pindex += OFF_TO_IDX(fs->object->backing_object_offset);
- VM_OBJECT_WUNLOCK(fs->object);
+ vm_fault_object_unlock(fs, *objlocked);
fs->object = next_object;
+ *objlocked = RLOCK;
return (true);
}
@@ -1348,7 +1411,7 @@
* page except, perhaps, to pmap it.
*/
static void
-vm_fault_busy_sleep(struct faultstate *fs)
+vm_fault_busy_sleep(struct faultstate *fs, enum object_locked objlocked)
{
/*
* Reference the page before unlocking and
@@ -1364,7 +1427,7 @@
unlock_map(fs);
if (fs->m != vm_page_lookup(fs->object, fs->pindex) ||
!vm_page_busy_sleep(fs->m, "vmpfw", 0))
- VM_OBJECT_WUNLOCK(fs->object);
+ vm_fault_object_unlock(fs, objlocked);
VM_CNT_INC(v_intrans);
vm_object_deallocate(fs->first_object);
}
@@ -1378,19 +1441,24 @@
* Otherwise, the object will be unlocked upon return.
*/
static enum fault_status
-vm_fault_object(struct faultstate *fs, int *behindp, int *aheadp)
+vm_fault_object(struct faultstate *fs, int *behindp, int *aheadp,
+ enum object_locked *objlocked)
{
enum fault_status res;
bool dead;
+ VM_OBJECT_ASSERT_LOCKED(fs->object);
+
+again:
/*
* If the object is marked for imminent termination, we retry
* here, since the collapse pass has raced with us. Otherwise,
* if we see terminally dead object, return fail.
*/
- if ((fs->object->flags & OBJ_DEAD) != 0) {
+ if (__predict_false((fs->object->flags & OBJ_DEAD) != 0)) {
dead = fs->object->type == OBJT_DEAD;
- unlock_and_deallocate(fs);
+ vm_fault_object_unlock(fs, *objlocked);
+ fault_deallocate(fs);
if (dead)
return (FAULT_PROTECTION_FAILURE);
pause("vmf_de", 1);
@@ -1403,7 +1471,7 @@
fs->m = vm_page_lookup(fs->object, fs->pindex);
if (fs->m != NULL) {
if (!vm_page_tryxbusy(fs->m)) {
- vm_fault_busy_sleep(fs);
+ vm_fault_busy_sleep(fs, *objlocked);
return (FAULT_RESTART);
}
@@ -1413,10 +1481,14 @@
* done.
*/
if (vm_page_all_valid(fs->m)) {
- VM_OBJECT_WUNLOCK(fs->object);
+ vm_fault_object_unlock(fs, *objlocked);
return (FAULT_SOFT);
}
}
+
+ if (!vm_fault_object_upgrade_cond(fs, objlocked))
+ goto again;
+
VM_OBJECT_ASSERT_WLOCKED(fs->object);
/*
@@ -1465,6 +1537,7 @@
struct faultstate fs;
int ahead, behind, faultcount, rv;
enum fault_status res;
+ enum object_locked objlocked;
bool hardfault;
VM_CNT_INC(v_vm_faults);
@@ -1557,11 +1630,12 @@
}
}
+ objlocked = WLOCK;
while (TRUE) {
KASSERT(fs.m == NULL,
("page still set %p at loop start", fs.m));
- res = vm_fault_object(&fs, &behind, &ahead);
+ res = vm_fault_object(&fs, &behind, &ahead, &objlocked);
switch (res) {
case FAULT_SOFT:
goto found;
@@ -1590,15 +1664,16 @@
* traverse into a backing object or zero fill if none is
* found.
*/
- if (vm_fault_next(&fs))
+ if (vm_fault_next(&fs, &objlocked))
continue;
if ((fs.fault_flags & VM_FAULT_NOFILL) != 0) {
if (fs.first_object == fs.object)
fault_page_free(&fs.first_m);
- unlock_and_deallocate(&fs);
+ vm_fault_object_unlock(&fs, objlocked);
+ fault_deallocate(&fs);
return (KERN_OUT_OF_BOUNDS);
}
- VM_OBJECT_WUNLOCK(fs.object);
+ vm_fault_object_unlock(&fs, objlocked);
vm_fault_zerofill(&fs);
/* Don't try to prefault neighboring pages. */
faultcount = 1;

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