Author: mjg
Date: Fri Aug 21 21:24:14 2020
New Revision: 364464
URL: https://svnweb.freebsd.org/changeset/base/364464
Log:
vfs: fix freevnode accounting
Most notably add the missing decrement to vhold_smr.
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Reported by: Dan Nelson <dnelson_1...@yahoo.com>
Fixes: r362827 ("vfs: protect vnodes with smr")
Modified:
head/sys/kern/vfs_subr.c
Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c Fri Aug 21 20:10:29 2020 (r364463)
+++ head/sys/kern/vfs_subr.c Fri Aug 21 21:24:14 2020 (r364464)
@@ -1293,6 +1293,28 @@ static int vnlruproc_sig;
*/
#define VNLRU_FREEVNODES_SLOP 128
+static __inline void
+vn_freevnodes_inc(void)
+{
+ struct vdbatch *vd;
+
+ critical_enter();
+ vd = DPCPU_PTR(vd);
+ vd->freevnodes++;
+ critical_exit();
+}
+
+static __inline void
+vn_freevnodes_dec(void)
+{
+ struct vdbatch *vd;
+
+ critical_enter();
+ vd = DPCPU_PTR(vd);
+ vd->freevnodes--;
+ critical_exit();
+}
+
static u_long
vnlru_read_freevnodes(void)
{
@@ -3195,19 +3217,14 @@ vunref(struct vnode *vp)
void
vhold(struct vnode *vp)
{
- struct vdbatch *vd;
int old;
CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
old = atomic_fetchadd_int(&vp->v_holdcnt, 1);
VNASSERT(old >= 0 && (old & VHOLD_ALL_FLAGS) == 0, vp,
("%s: wrong hold count %d", __func__, old));
- if (old != 0)
- return;
- critical_enter();
- vd = DPCPU_PTR(vd);
- vd->freevnodes--;
- critical_exit();
+ if (old == 0)
+ vn_freevnodes_dec();
}
void
@@ -3268,8 +3285,11 @@ vhold_smr(struct vnode *vp)
}
VNASSERT(count >= 0, vp, ("invalid hold count %d\n", count));
- if (atomic_fcmpset_int(&vp->v_holdcnt, &count, count + 1))
+ if (atomic_fcmpset_int(&vp->v_holdcnt, &count, count + 1)) {
+ if (count == 0)
+ vn_freevnodes_dec();
return (true);
+ }
}
}
@@ -3309,17 +3329,13 @@ vdbatch_enqueue(struct vnode *vp)
VNASSERT(!VN_IS_DOOMED(vp), vp,
("%s: deferring requeue of a doomed vnode", __func__));
- critical_enter();
- vd = DPCPU_PTR(vd);
- vd->freevnodes++;
if (vp->v_dbatchcpu != NOCPU) {
VI_UNLOCK(vp);
- critical_exit();
return;
}
sched_pin();
- critical_exit();
+ vd = DPCPU_PTR(vd);
mtx_lock(&vd->lock);
MPASS(vd->index < VDBATCH_SIZE);
MPASS(vd->tab[vd->index] == NULL);
@@ -3444,6 +3460,7 @@ vdropl(struct vnode *vp)
return;
}
if (!VN_IS_DOOMED(vp)) {
+ vn_freevnodes_inc();
vdrop_deactivate(vp);
/*
* Also unlocks the interlock. We can't assert on it as we
@@ -3458,7 +3475,8 @@ vdropl(struct vnode *vp)
* We may be racing against vhold_smr. If they win we can just pretend
* we never got this far, they will vdrop later.
*/
- if (!atomic_cmpset_int(&vp->v_holdcnt, 0, VHOLD_NO_SMR)) {
+ if (__predict_false(!atomic_cmpset_int(&vp->v_holdcnt, 0,
VHOLD_NO_SMR))) {
+ vn_freevnodes_inc();
VI_UNLOCK(vp);
/*
* We lost the aforementioned race. Any subsequent access is
@@ -3466,6 +3484,9 @@ vdropl(struct vnode *vp)
*/
return;
}
+ /*
+ * Don't bump freevnodes as this one is going away.
+ */
freevnode(vp);
}
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