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ZFS vn_rele_async: catch up with the use of refcount(9) for the vnode use count

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It's not sufficient nor required to use the vnode interlock when
checking if we are going to drop the last use count as the code in
vputx() uses refcount (atomic) operations for both checking and
decrementing the use code.  Apply the same method to vn_rele_async().
While here, remove vn_rele_inactive(), a wrapper around vrele() that
didn't add any value.

Also, the change required making vfs_refcount_release_if_not_last()
public.  I've made vfs_refcount_acquire_if_not_zero() public as well.
They are in sys/refcount.h now.  While making the move I've dropped the
vfs_ prefix.

Reviewed by:	mjg
MFC after:	2 weeks
Sponsored by:	Panzura
Differential Revision: https://reviews.freebsd.org/D14869
This commit is contained in:
Andriy Gapon 2018-03-28 08:55:31 +00:00
parent 6472fa9a9d
commit f4043145f2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=331666
3 changed files with 42 additions and 51 deletions
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17
sys/cddl/contrib/opensolaris/uts/common/fs/vnode.c
View File

@ -72,12 +72,6 @@ xva_getxoptattr(xvattr_t *xvap)
return (xoap);
}
static void
vn_rele_inactive(vnode_t *vp)
{
vrele(vp);
}
/*
* Like vn_rele() except if we are going to call VOP_INACTIVE() then do it
* asynchronously using a taskq. This can avoid deadlocks caused by re-entering
@ -92,13 +86,10 @@ void
vn_rele_async(vnode_t *vp, taskq_t *taskq)
{
VERIFY(vp->v_count > 0);
VI_LOCK(vp);
if (vp->v_count == 1 && !(vp->v_iflag & VI_DOINGINACT)) {
VI_UNLOCK(vp);
VERIFY(taskq_dispatch((taskq_t *)taskq,
(task_func_t *)vn_rele_inactive, vp, TQ_SLEEP) != 0);
if (refcount_release_if_not_last(&vp->v_usecount)) {
vdrop(vp);
return;
}
refcount_release(&vp->v_usecount);
vdropl(vp);
VERIFY(taskq_dispatch((taskq_t *)taskq,
(task_func_t *)vrele, vp, TQ_SLEEP) != 0);
}

45
sys/kern/vfs_subr.c
View File

@ -2455,37 +2455,6 @@ reassignbuf(struct buf *bp)
BO_UNLOCK(bo);
}
/*
* A temporary hack until refcount_* APIs are sorted out.
*/
static __inline int
vfs_refcount_acquire_if_not_zero(volatile u_int *count)
{
u_int old;
old = *count;
for (;;) {
if (old == 0)
return (0);
if (atomic_fcmpset_int(count, &old, old + 1))
return (1);
}
}
static __inline int
vfs_refcount_release_if_not_last(volatile u_int *count)
{
u_int old;
old = *count;
for (;;) {
if (old == 1)
return (0);
if (atomic_fcmpset_int(count, &old, old - 1))
return (1);
}
}
static void
v_init_counters(struct vnode *vp)
{
@ -2524,7 +2493,7 @@ v_incr_usecount(struct vnode *vp)
CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
if (vp->v_type != VCHR &&
vfs_refcount_acquire_if_not_zero(&vp->v_usecount)) {
refcount_acquire_if_not_zero(&vp->v_usecount)) {
VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
("vnode with usecount and VI_OWEINACT set"));
} else {
@ -2616,7 +2585,7 @@ vget(struct vnode *vp, int flags, struct thread *td)
* Upgrade our holdcnt to a usecount.
*/
if (vp->v_type == VCHR ||
!vfs_refcount_acquire_if_not_zero(&vp->v_usecount)) {
!refcount_acquire_if_not_zero(&vp->v_usecount)) {
VI_LOCK(vp);
if ((vp->v_iflag & VI_OWEINACT) == 0) {
oweinact = 0;
@ -2720,7 +2689,7 @@ vputx(struct vnode *vp, int func)
CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
if (vp->v_type != VCHR &&
vfs_refcount_release_if_not_last(&vp->v_usecount)) {
refcount_release_if_not_last(&vp->v_usecount)) {
if (func == VPUTX_VPUT)
VOP_UNLOCK(vp, 0);
vdrop(vp);
@ -2836,7 +2805,7 @@ _vhold(struct vnode *vp, bool locked)
ASSERT_VI_UNLOCKED(vp, __func__);
CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
if (!locked) {
if (vfs_refcount_acquire_if_not_zero(&vp->v_holdcnt)) {
if (refcount_acquire_if_not_zero(&vp->v_holdcnt)) {
VNASSERT((vp->v_iflag & VI_FREE) == 0, vp,
("_vhold: vnode with holdcnt is free"));
return;
@ -2907,7 +2876,7 @@ _vdrop(struct vnode *vp, bool locked)
if ((int)vp->v_holdcnt <= 0)
panic("vdrop: holdcnt %d", vp->v_holdcnt);
if (!locked) {
if (vfs_refcount_release_if_not_last(&vp->v_holdcnt))
if (refcount_release_if_not_last(&vp->v_holdcnt))
return;
VI_LOCK(vp);
}
@ -5438,12 +5407,12 @@ mnt_vnode_next_active_relock(struct vnode *mvp, struct mount *mp,
* acquired with vhold(), but that might try to acquire the vnode
* interlock, which would be a LOR with the mount vnode list lock.
*/
held = vfs_refcount_acquire_if_not_zero(&vp->v_holdcnt);
held = refcount_acquire_if_not_zero(&vp->v_holdcnt);
mtx_unlock(&mp->mnt_listmtx);
if (!held)
goto abort;
VI_LOCK(vp);
if (!vfs_refcount_release_if_not_last(&vp->v_holdcnt)) {
if (!refcount_release_if_not_last(&vp->v_holdcnt)) {
vdropl(vp);
goto abort;
}

31
sys/sys/refcount.h
View File

@ -76,4 +76,35 @@ refcount_release(volatile u_int *count)
return (1);
}
/*
* A temporary hack until refcount_* APIs are sorted out.
*/
static __inline int
refcount_acquire_if_not_zero(volatile u_int *count)
{
u_int old;
old = *count;
for (;;) {
if (old == 0)
return (0);
if (atomic_fcmpset_int(count, &old, old + 1))
return (1);
}
}
static __inline int
refcount_release_if_not_last(volatile u_int *count)
{
u_int old;
old = *count;
for (;;) {
if (old == 1)
return (0);
if (atomic_fcmpset_int(count, &old, old - 1))
return (1);
}
}
#endif /* ! __SYS_REFCOUNT_H__ */