Page MenuHomeFreeBSD
Files F158266914

D23185.id66764.diff
No OneTemporary
Actions

D23185.id66764.diff
View Options

Index: sys/kern/vfs_subr.c
===================================================================
--- sys/kern/vfs_subr.c
+++ sys/kern/vfs_subr.c
@@ -2756,13 +2756,10 @@
* see doomed vnodes. If inactive processing was delayed in
* vput try to do it here.
*
- * Both holdcnt and usecount can be manipulated using atomics without holding
- * any locks except in these cases which require the vnode interlock:
- * holdcnt: 1->0 and 0->1
- * usecount: 0->1
+ * usecount is manipulated using atomics without holding any locks.
*
- * usecount is permitted to transition 1->0 without the interlock because
- * vnode is kept live by holdcnt.
+ * holdcnt can be manipulated using atomics without holding any locks,
+ * except when transitioning 1<->0, in which case the interlock is held.
*/
static enum vgetstate __always_inline
_vget_prep(struct vnode *vp, bool interlock)
@@ -2799,10 +2796,46 @@
return (vget_finish(vp, flags, vs));
}
+static int __noinline
+vget_finish_vchr(struct vnode *vp)
+{
+
+ VNASSERT(vp->v_type == VCHR, vp, ("type != VCHR)"));
+
+ /*
+ * See the comment in vget_finish before usecount bump.
+ */
+ if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
+#ifdef INVARIANTS
+ int old = atomic_fetchadd_int(&vp->v_holdcnt, -1);
+ VNASSERT(old > 0, vp, ("%s: wrong hold count %d", __func__, old));
+#else
+ refcount_release(&vp->v_holdcnt);
+#endif
+ return (0);
+ }
+
+ VI_LOCK(vp);
+ if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
+#ifdef INVARIANTS
+ int old = atomic_fetchadd_int(&vp->v_holdcnt, -1);
+ VNASSERT(old > 1, vp, ("%s: wrong hold count %d", __func__, old));
+#else
+ refcount_release(&vp->v_holdcnt);
+#endif
+ VI_UNLOCK(vp);
+ return (0);
+ }
+ v_incr_devcount(vp);
+ refcount_acquire(&vp->v_usecount);
+ VI_UNLOCK(vp);
+ return (0);
+}
+
int
vget_finish(struct vnode *vp, int flags, enum vgetstate vs)
{
- int error;
+ int error, old;
VNASSERT((flags & LK_TYPE_MASK) != 0, vp,
("%s: invalid lock operation", __func__));
@@ -2832,69 +2865,106 @@
return (0);
}
+ if (__predict_false(vp->v_type == VCHR))
+ return (vget_finish_vchr(vp));
+
/*
* We hold the vnode. If the usecount is 0 it will be utilized to keep
* the vnode around. Otherwise someone else lended their hold count and
* we have to drop ours.
*/
- if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
+ old = atomic_fetchadd_int(&vp->v_usecount, 1);
+ VNASSERT(old >= 0, vp, ("%s: wrong use count %d", __func__, old));
+ if (old != 0) {
#ifdef INVARIANTS
- int old = atomic_fetchadd_int(&vp->v_holdcnt, -1);
+ old = atomic_fetchadd_int(&vp->v_holdcnt, -1);
VNASSERT(old > 1, vp, ("%s: wrong hold count %d", __func__, old));
#else
refcount_release(&vp->v_holdcnt);
#endif
- return (0);
}
+ return (0);
+}
+
+/*
+ * Increase the reference (use) and hold count of a vnode.
+ * This will also remove the vnode from the free list if it is presently free.
+ */
+static void
+vref_vchr(struct vnode *vp, bool interlock)
+{
/*
- * We don't guarantee that any particular close will
- * trigger inactive processing so just make a best effort
- * here at preventing a reference to a removed file. If
- * we don't succeed no harm is done.
- *
- * Upgrade our holdcnt to a usecount.
- */
- VI_LOCK(vp);
- /*
- * See the previous section. By the time we get here we may find
- * ourselves in the same spot.
+ * See the comment in vget_finish before usecount bump.
*/
+ if (!interlock) {
+ if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
+ VNODE_REFCOUNT_FENCE_ACQ();
+ VNASSERT(vp->v_holdcnt > 0, vp,
+ ("%s: active vnode not held", __func__));
+ return;
+ }
+ VI_LOCK(vp);
+ /*
+ * By the time we get here the vnode might have been doomed, at
+ * which point the 0->1 use count transition is no longer
+ * protected by the interlock. Since it can't bounce back to
+ * VCHR and requires vref semantics, punt it back
+ */
+ if (__predict_false(vp->v_type == VBAD)) {
+ VI_UNLOCK(vp);
+ vref(vp);
+ return;
+ }
+ }
+ VNASSERT(vp->v_type == VCHR, vp, ("type != VCHR)"));
if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
-#ifdef INVARIANTS
- int old = atomic_fetchadd_int(&vp->v_holdcnt, -1);
- VNASSERT(old > 1, vp, ("%s: wrong hold count %d", __func__, old));
-#else
- refcount_release(&vp->v_holdcnt);
-#endif
- VI_UNLOCK(vp);
- return (0);
+ VNODE_REFCOUNT_FENCE_ACQ();
+ VNASSERT(vp->v_holdcnt > 0, vp,
+ ("%s: active vnode not held", __func__));
+ if (!interlock)
+ VI_UNLOCK(vp);
+ return;
}
+ vhold(vp);
v_incr_devcount(vp);
refcount_acquire(&vp->v_usecount);
- VI_UNLOCK(vp);
- return (0);
+ if (!interlock)
+ VI_UNLOCK(vp);
+ return;
}
-/*
- * Increase the reference (use) and hold count of a vnode.
- * This will also remove the vnode from the free list if it is presently free.
- */
void
vref(struct vnode *vp)
{
+ int old;
- ASSERT_VI_UNLOCKED(vp, __func__);
CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
+ if (__predict_false(vp->v_type == VCHR)) {
+ vref_vchr(vp, false);
+ return;
+ }
+
if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
VNODE_REFCOUNT_FENCE_ACQ();
VNASSERT(vp->v_holdcnt > 0, vp,
("%s: active vnode not held", __func__));
return;
}
- VI_LOCK(vp);
- vrefl(vp);
- VI_UNLOCK(vp);
+ vhold(vp);
+ /*
+ * See the comment in vget_finish.
+ */
+ old = atomic_fetchadd_int(&vp->v_usecount, 1);
+ VNASSERT(old >= 0, vp, ("%s: wrong use count %d", __func__, old));
+ if (old != 0) {
+#ifdef INVARIANTS
+ old = atomic_fetchadd_int(&vp->v_holdcnt, -1);
+ VNASSERT(old > 1, vp, ("%s: wrong hold count %d", __func__, old));
+#else
+ refcount_release(&vp->v_holdcnt);
+#endif
+ }
}
void
@@ -2903,15 +2973,11 @@
ASSERT_VI_LOCKED(vp, __func__);
CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
- if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
- VNODE_REFCOUNT_FENCE_ACQ();
- VNASSERT(vp->v_holdcnt > 0, vp,
- ("%s: active vnode not held", __func__));
+ if (__predict_false(vp->v_type == VCHR)) {
+ vref_vchr(vp, true);
return;
}
- vholdl(vp);
- v_incr_devcount(vp);
- refcount_acquire(&vp->v_usecount);
+ vref(vp);
}
void
@@ -3079,8 +3145,6 @@
}
break;
}
- VNASSERT(vp->v_usecount == 0 || (vp->v_iflag & VI_OWEINACT) == 0, vp,
- ("vnode with usecount and VI_OWEINACT set"));
if (error == 0) {
vinactive(vp);
if (func != VPUTX_VUNREF)

File Metadata

Mime Type
text/plain
Expires
Sun, May 31, 2:14 PM (15 h, 2 m)
Storage Engine
blob
Storage Format
Raw Data
Storage Handle
33652640
Default Alt Text
D23185.id66764.diff (6 KB)

Event Timeline