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unionfs: Improve locking assertions

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Add an assertion to unionfs_node_update() that the upper vnode is
exclusively locked; we already make the same assertion for the lower
vnode.
Also, assert in unionfs_noderem() that the vnode lock is not recursed
and acquire v_lock with LK_NOWAIT.  Since v_lock is not the active
lock for the vnode at this point, it should not be contended.
Finally, remove VDIR assertions from unionfs_get_cached_vnode().
lvp/uvp will be referenced but not locked at this point, so v_type
may concurrently change due to vgonel().  The cached unionfs node,
if one exists, would only have made it into the cache if lvp/uvp
were of type VDIR at the time of insertion; the corresponding
VDIR assert in unionfs_ins_cached_vnode() should be safe because
lvp/uvp will be locked by that time and will not be used if either
is doomed.

Noted by:	kib
Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D32629
This commit is contained in:
Jason A. Harmening 2021-10-27 22:31:16 -07:00
parent 3ecefc4a61
commit 66191a76ac
1 changed files with 6 additions and 6 deletions
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12
sys/fs/unionfs/union_subr.c
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@ -183,11 +183,6 @@ unionfs_get_cached_vnode(struct vnode *uvp, struct vnode *lvp,
{
struct vnode *vp;
KASSERT(uvp == NULLVP || uvp->v_type == VDIR,
("%s: v_type != VDIR", __func__));
KASSERT(lvp == NULLVP || lvp->v_type == VDIR,
("%s: v_type != VDIR", __func__));
vp = NULLVP;
VI_LOCK(dvp);
if (uvp != NULLVP)
@ -209,6 +204,8 @@ unionfs_ins_cached_vnode(struct unionfs_node *uncp,
struct unionfs_node_hashhead *hd;
struct vnode *vp;
ASSERT_VOP_ELOCKED(uncp->un_uppervp, __func__);
ASSERT_VOP_ELOCKED(uncp->un_lowervp, __func__);
KASSERT(uncp->un_uppervp == NULLVP || uncp->un_uppervp->v_type == VDIR,
("%s: v_type != VDIR", __func__));
KASSERT(uncp->un_lowervp == NULLVP || uncp->un_lowervp->v_type == VDIR,
@ -439,7 +436,9 @@ unionfs_noderem(struct vnode *vp, struct thread *td)
struct vnode *dvp;
int count;
if (lockmgr(&(vp->v_lock), LK_EXCLUSIVE, NULL) != 0)
KASSERT(vp->v_vnlock->lk_recurse == 0,
("%s: vnode %p locked recursively", __func__, vp));
if (lockmgr(&vp->v_lock, LK_EXCLUSIVE | LK_NOWAIT, NULL) != 0)
panic("%s: failed to acquire lock for vnode lock", __func__);
/*
@ -803,6 +802,7 @@ unionfs_node_update(struct unionfs_node *unp, struct vnode *uvp,
vp = UNIONFSTOV(unp);
lvp = unp->un_lowervp;
ASSERT_VOP_ELOCKED(lvp, __func__);
ASSERT_VOP_ELOCKED(uvp, __func__);
dvp = unp->un_dvp;
/*