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vfs: fix freevnode accounting

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Most notably add the missing decrement to vhold_smr.

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Reported by:	Dan Nelson <dnelson_1901@yahoo.com>
Fixes:	r362827 ("vfs: protect vnodes with smr")
This commit is contained in:
Mateusz Guzik 2020-08-21 21:24:14 +00:00
parent 7758c80f74
commit 19337211f8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=364464
1 changed files with 35 additions and 14 deletions
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49
sys/kern/vfs_subr.c
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@ -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);
}