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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
@@ -127,6 +127,7 @@
vm_prot_t prot;
int fault_flags;
boolean_t wired;
+ bool can_read_lock;
/* Control state. */
struct timeval oom_start_time;
@@ -212,7 +213,7 @@
m = *mp;
if (m != NULL) {
- VM_OBJECT_ASSERT_WLOCKED(m->object);
+ VM_OBJECT_ASSERT_LOCKED(m->object);
if (!vm_page_wired(m))
vm_page_free(m);
else
@@ -278,7 +279,7 @@
unlock_and_deallocate(struct faultstate *fs)
{
- VM_OBJECT_WUNLOCK(fs->object);
+ VM_OBJECT_UNLOCK(fs->object);
fault_deallocate(fs);
}
@@ -1047,6 +1048,11 @@
{
vm_object_t next_object;
+ if (fs->object == fs->first_object || !fs->can_read_lock)
+ VM_OBJECT_ASSERT_WLOCKED(fs->object);
+ else
+ VM_OBJECT_ASSERT_LOCKED(fs->object);
+
/*
* The requested page does not exist at this object/
* offset. Remove the invalid page from the object,
@@ -1067,18 +1073,20 @@
* 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);
+ if (fs->can_read_lock)
+ VM_OBJECT_RLOCK(next_object);
+ else
+ VM_OBJECT_WLOCK(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_OBJECT_UNLOCK(fs->object);
fs->object = next_object;
return (true);
@@ -1363,7 +1371,7 @@
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_OBJECT_UNLOCK(fs->object);
VM_CNT_INC(v_intrans);
vm_object_deallocate(fs->first_object);
}
@@ -1382,6 +1390,11 @@
enum fault_status res;
bool dead;
+ if (fs->object == fs->first_object || !fs->can_read_lock)
+ VM_OBJECT_ASSERT_WLOCKED(fs->object);
+ else
+ VM_OBJECT_ASSERT_LOCKED(fs->object);
+
/*
* If the object is marked for imminent termination, we retry
* here, since the collapse pass has raced with us. Otherwise,
@@ -1412,11 +1425,10 @@
* done.
*/
if (vm_page_all_valid(fs->m)) {
- VM_OBJECT_WUNLOCK(fs->object);
+ VM_OBJECT_UNLOCK(fs->object);
return (FAULT_SOFT);
}
}
- VM_OBJECT_ASSERT_WLOCKED(fs->object);
/*
* Page is not resident. If the pager might contain the page
@@ -1425,6 +1437,12 @@
*/
if (fs->m == NULL && (fault_object_needs_getpages(fs->object) ||
fs->object == fs->first_object)) {
+ if (!VM_OBJECT_WOWNED(fs->object) && !VM_OBJECT_TRYUPGRADE(fs->object)) {
+ MPASS(fs->can_read_lock);
+ fs->can_read_lock = false;
+ unlock_and_deallocate(fs);
+ return (FAULT_RESTART);
+ }
res = vm_fault_allocate(fs);
if (res != FAULT_CONTINUE)
return (res);
@@ -1447,10 +1465,14 @@
* prevents simultaneous faults and collapses while
* the object lock is dropped.
*/
- VM_OBJECT_WUNLOCK(fs->object);
+ VM_OBJECT_UNLOCK(fs->object);
res = vm_fault_getpages(fs, behindp, aheadp);
- if (res == FAULT_CONTINUE)
- VM_OBJECT_WLOCK(fs->object);
+ if (res == FAULT_CONTINUE) {
+ if (fs->object == fs->first_object || !fs->can_read_lock)
+ VM_OBJECT_WLOCK(fs->object);
+ else
+ VM_OBJECT_RLOCK(fs->object);
+ }
} else {
res = FAULT_CONTINUE;
}
@@ -1479,6 +1501,7 @@
fs.lookup_still_valid = false;
fs.oom_started = false;
fs.nera = -1;
+ fs.can_read_lock = true;
faultcount = 0;
hardfault = false;
@@ -1597,7 +1620,7 @@
unlock_and_deallocate(&fs);
return (KERN_OUT_OF_BOUNDS);
}
- VM_OBJECT_WUNLOCK(fs.object);
+ VM_OBJECT_UNLOCK(fs.object);
vm_fault_zerofill(&fs);
/* Don't try to prefault neighboring pages. */
faultcount = 1;
diff --git a/sys/vm/vm_object.h b/sys/vm/vm_object.h
--- a/sys/vm/vm_object.h
+++ b/sys/vm/vm_object.h
@@ -267,6 +267,8 @@
rw_wowned(&(object)->lock)
#define VM_OBJECT_WUNLOCK(object) \
rw_wunlock(&(object)->lock)
+#define VM_OBJECT_UNLOCK(object) \
+ rw_unlock(&(object)->lock)
#define VM_OBJECT_DROP(object) \
lock_class_rw.lc_unlock(&(object)->lock.lock_object)
#define VM_OBJECT_PICKUP(object, state) \

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