Thanks Mouse and Martin. I got past that error. But
now I'm running into another problem - unable to
determine when write op occurs (to be able to return
ENOSPC error).
I'm trying to use the 'bypass routine' by creating a
new `full_bypass` by duplicating `layer_bypass`. In this
`full_bypass` I want to return ENOSPC error whenever
write occurs. Which variable contains this info? I'm
confused which structs contain what information.
-- IC
full_bypass for reference:
int
full_bypass(void *v)
{
struct vop_generic_args /* {
struct vnodeop_desc *a_desc;
<other random data follows, presumably>
} */ *ap = v;
int (**our_vnodeop_p)(void *);
struct vnode **this_vp_p;
int error;
struct vnode *old_vps[VDESC_MAX_VPS], *vp0;
struct vnode **vps_p[VDESC_MAX_VPS];
struct vnode ***vppp;
struct mount *mp;
struct vnodeop_desc *descp = ap->a_desc;
int reles, i, flags;
#ifdef DIAGNOSTIC
/*
* We require at least one vp.
*/
if (descp->vdesc_vp_offsets == NULL ||
descp->vdesc_vp_offsets[0] == VDESC_NO_OFFSET)
panic("%s: no vp's in map.\n", __func__);
#endif
vps_p[0] =
VOPARG_OFFSETTO(struct vnode**, descp->vdesc_vp_offsets[0], ap);
vp0 = *vps_p[0];
mp = vp0->v_mount;
flags = MOUNTTOLAYERMOUNT(mp)->layerm_flags;
our_vnodeop_p = vp0->v_op;
if (flags & LAYERFS_MBYPASSDEBUG)
printf("%s: %s\n", __func__, descp->vdesc_name);
/*
* Map the vnodes going in.
* Later, we'll invoke the operation based on
* the first mapped vnode's operation vector.
*/
reles = descp->vdesc_flags;
for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) {
if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET)
break; /* bail out at end of list */
vps_p[i] = this_vp_p =
VOPARG_OFFSETTO(struct vnode**, descp->vdesc_vp_offsets[i],
ap);
/*
* We're not guaranteed that any but the first vnode
* are of our type. Check for and don't map any
* that aren't. (We must always map first vp or vclean fails.)
*/
if (i && (*this_vp_p == NULL ||
(*this_vp_p)->v_op != our_vnodeop_p)) {
old_vps[i] = NULL;
} else {
old_vps[i] = *this_vp_p;
*(vps_p[i]) = LAYERVPTOLOWERVP(*this_vp_p);
/*
* XXX - Several operations have the side effect
* of vrele'ing their vp's. We must account for
* that. (This should go away in the future.)
*/
if (reles & VDESC_VP0_WILLRELE)
vref(*this_vp_p);
}
}
///////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////
I want to return ENOSPC here
if there is a write operation
///////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////
/*
* Call the operation on the lower layer
* with the modified argument structure.
*/
error = VCALL(*vps_p[0], descp->vdesc_offset, ap);
/*
* Maintain the illusion of call-by-value
* by restoring vnodes in the argument structure
* to their original value.
*/
reles = descp->vdesc_flags;
for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) {
if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET)
break; /* bail out at end of list */
if (old_vps[i]) {
*(vps_p[i]) = old_vps[i];
if (reles & VDESC_VP0_WILLRELE)
vrele(*(vps_p[i]));
}
}
/*
* Map the possible out-going vpp
* (Assumes that the lower layer always returns
* a VREF'ed vpp unless it gets an error.)
*/
if (descp->vdesc_vpp_offset != VDESC_NO_OFFSET && !error) {
vppp = VOPARG_OFFSETTO(struct vnode***,
descp->vdesc_vpp_offset, ap);
/*
* Only vop_lookup, vop_create, vop_makedir, vop_mknod
* and vop_symlink return vpp's. vop_lookup doesn't call bypass
* as a lookup on "." would generate a locking error.
* So all the calls which get us here have a unlocked vpp. :-)
*/
error = layer_node_create(mp, **vppp, *vppp);
if (error) {
vrele(**vppp);
**vppp = NULL;
}
}
return error;
}
