Quoting Dan Smith (danms@xxxxxxxxxx):
> OL> Both look good.
>
> Okay, but per Serge's suggestion shall we change the restore_obj() to
> the one included below? :)
>
> --
> Dan Smith
> IBM Linux Technology Center
> email: danms@xxxxxxxxxx
>
> commit d0c71c159decd47c4a6f9778d02dc521b74ff414
> Author: Dan Smith <danms@xxxxxxxxxx>
> Date: Tue Feb 9 14:04:23 2010 -0800
>
> Make restore_obj() tolerate a preexisting object in the hash (v2)
>
> ... as long as the pointer is the same as that returned from the restore
> function. Also move the compulsory ref_drop() so that it only gets
> done if we created the new object.
>
> The existing object tolerance is important for netdev restore because it
> means that I can refer to a peer by its objref instead of needing the
> (previously-rejected) veth_peer() function. If this is not acceptable,
> then I'll need to keep a separate list of pairs.
>
> Changes in v2:
> - Check that the type of the object already in the hash matches that
> of the objref header we're reading.
> - Add a comment about why and how we might get into this sort of
> situation.
>
> Signed-off-by: Dan Smith <danms@xxxxxxxxxx>
Acked-by: Serge Hallyn <serue@xxxxxxxxxx>
/me thinks he'd better send a patch defining CKPT_OBJ_LASTREF to help out
those poor ->obj_ref(x, 0) who so badly want to be more informative...
thanks,
-serge
>
> diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
> index 0b06b06..4ca7799 100644
> --- a/checkpoint/objhash.c
> +++ b/checkpoint/objhash.c
> @@ -1059,16 +1059,29 @@ int restore_obj(struct ckpt_ctx *ctx, struct ckpt_hdr_ob
> if (IS_ERR(ptr))
> return PTR_ERR(ptr);
>
> - if (obj_find_by_objref(ctx, h->objref))
> - obj = ERR_PTR(-EINVAL);
> - else
> + obj = obj_find_by_objref(ctx, h->objref);
> + if (!obj) {
> obj = obj_new(ctx, ptr, h->objref, h->objtype);
> - /*
> - * Drop an extra reference to the object returned by ops->restore:
> - * On success, this clears the extra reference taken by obj_new(),
> - * and on failure, this cleans up the object itself.
> - */
> - ops->ref_drop(ptr, 0);
> + /*
> + * Drop an extra reference to the object returned by
> + * ops->restore: On success, this clears the extra
> + * reference taken by obj_new(), and on failure, this
> + * cleans up the object itself.
> + */
> + ops->ref_drop(ptr, 0);
> + } else if ((obj->ptr != ptr) || (obj->ops->obj_type != h->objtype)) {
> + /* Normally, we expect an object to not already exist
> + * in the hash. However, for some special scenarios
> + * where we're restoring sets of objects that must be
> + * co-allocated (such, as veth netdev pairs) we need
> + * to tolerate this case if the second restore returns
> + * the correct type and pointer, as specified in the
> + * existing object. If either of those don't match,
> + * we fail.
> + */
> + obj = ERR_PTR(-EINVAL);
> + }
> +
> if (IS_ERR(obj)) {
> ops->ref_drop(ptr, 1);
> return PTR_ERR(obj);
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