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nullfs: provide special bypass for VOP_VPUT_PAIR

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Generic bypass cannot understand the rules of liveness for the VOP.

Reviewed by:	chs, mckusick
Tested by:	pho
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Konstantin Belousov 2021-01-24 15:22:48 +02:00
parent 49c117c193
commit e4aaf35ab5
1 changed files with 49 additions and 0 deletions
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49
sys/fs/nullfs/null_vnops.c
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@ -967,6 +967,54 @@ null_read_pgcache(struct vop_read_pgcache_args *ap)
return (error);
}
/*
* Avoid standard bypass, since lower dvp and vp could be no longer
* valid after vput().
*/
static int
null_vput_pair(struct vop_vput_pair_args *ap)
{
struct mount *mp;
struct vnode *dvp, *ldvp, *lvp, *vp, *vp1, **vpp;
int error, res;
dvp = ap->a_dvp;
ldvp = NULLVPTOLOWERVP(dvp);
vref(ldvp);
vpp = ap->a_vpp;
vp = NULL;
lvp = NULL;
if (vpp != NULL) {
vp = *vpp;
if (vp != NULL) {
vhold(vp);
mp = vp->v_mount;
lvp = NULLVPTOLOWERVP(vp);
if (ap->a_unlock_vp)
vref(lvp);
}
}
res = VOP_VPUT_PAIR(ldvp, &lvp, ap->a_unlock_vp);
/* lvp might have been unlocked and vp reclaimed */
if (vp != NULL) {
if (!ap->a_unlock_vp && vp->v_vnlock != lvp->v_vnlock) {
error = null_nodeget(mp, lvp, &vp1);
if (error == 0) {
vput(vp);
*vpp = vp1;
}
}
if (ap->a_unlock_vp)
vrele(vp);
vdrop(vp);
}
vrele(dvp);
return (res);
}
/*
* Global vfs data structures
*/
@ -997,5 +1045,6 @@ struct vop_vector null_vnodeops = {
.vop_vptocnp = null_vptocnp,
.vop_vptofh = null_vptofh,
.vop_add_writecount = null_add_writecount,
.vop_vput_pair = null_vput_pair,
};
VFS_VOP_VECTOR_REGISTER(null_vnodeops);