... 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>
---
checkpoint/objhash.c | 31 ++++++++++++++++++++++---------
1 files changed, 22 insertions(+), 9 deletions(-)
diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
index 7208382..65875e3 100644
--- a/checkpoint/objhash.c
+++ b/checkpoint/objhash.c
@@ -1064,16 +1064,29 @@ int restore_obj(struct ckpt_ctx *ctx, struct ckpt_hdr_objref *h)
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);
--
1.6.2.5
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