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Subjectlinux-next: manual merge of the tip tree with the rdma tree
Hi all,

Today's linux-next merge of the tip tree got a conflict in:

drivers/infiniband/core/rdma_core.c

between commit:

9867f5c6695f ("IB/uverbs: Convert 'bool exclusive' into an enum")

from the rdma tree and commit:

bfc18e389c7a ("atomics/treewide: Rename __atomic_add_unless() => atomic_fetch_add_unless()")

from the tip tree.

I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging. You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.

--
Cheers,
Stephen Rothwell

diff --cc drivers/infiniband/core/rdma_core.c
index 4235b9ddc2ad,475910ffbcb6..000000000000
--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@@ -122,206 -120,19 +122,206 @@@ static int uverbs_try_lock_object(struc
* concurrently, setting the counter to zero is enough for releasing
* this lock.
*/
- if (!exclusive)
+ switch (mode) {
+ case UVERBS_LOOKUP_READ:
- return __atomic_add_unless(&uobj->usecnt, 1, -1) == -1 ?
+ return atomic_fetch_add_unless(&uobj->usecnt, 1, -1) == -1 ?
-EBUSY : 0;
+ case UVERBS_LOOKUP_WRITE:
+ /* lock is exclusive */
+ return atomic_cmpxchg(&uobj->usecnt, 0, -1) == 0 ? 0 : -EBUSY;
+ case UVERBS_LOOKUP_DESTROY:
+ return 0;
+ }
+ return 0;
+}
+
+static void assert_uverbs_usecnt(struct ib_uobject *uobj,
+ enum rdma_lookup_mode mode)
+{
+#ifdef CONFIG_LOCKDEP
+ switch (mode) {
+ case UVERBS_LOOKUP_READ:
+ WARN_ON(atomic_read(&uobj->usecnt) <= 0);
+ break;
+ case UVERBS_LOOKUP_WRITE:
+ WARN_ON(atomic_read(&uobj->usecnt) != -1);
+ break;
+ case UVERBS_LOOKUP_DESTROY:
+ break;
+ }
+#endif
+}
+
+/*
+ * This must be called with the hw_destroy_rwsem locked for read or write,
+ * also the uobject itself must be locked for write.
+ *
+ * Upon return the HW object is guaranteed to be destroyed.
+ *
+ * For RDMA_REMOVE_ABORT, the hw_destroy_rwsem is not required to be held,
+ * however the type's allocat_commit function cannot have been called and the
+ * uobject cannot be on the uobjects_lists
+ *
+ * For RDMA_REMOVE_DESTROY the caller shold be holding a kref (eg via
+ * rdma_lookup_get_uobject) and the object is left in a state where the caller
+ * needs to call rdma_lookup_put_uobject.
+ *
+ * For all other destroy modes this function internally unlocks the uobject
+ * and consumes the kref on the uobj.
+ */
+static int uverbs_destroy_uobject(struct ib_uobject *uobj,
+ enum rdma_remove_reason reason)
+{
+ struct ib_uverbs_file *ufile = uobj->ufile;
+ unsigned long flags;
+ int ret;
+
+ lockdep_assert_held(&ufile->hw_destroy_rwsem);
+ assert_uverbs_usecnt(uobj, UVERBS_LOOKUP_WRITE);
+
+ if (uobj->object) {
+ ret = uobj->type->type_class->destroy_hw(uobj, reason);
+ if (ret) {
+ if (ib_is_destroy_retryable(ret, reason, uobj))
+ return ret;
+
+ /* Nothing to be done, dangle the memory and move on */
+ WARN(true,
+ "ib_uverbs: failed to remove uobject id %d, driver err=%d",
+ uobj->id, ret);
+ }
+
+ uobj->object = NULL;
+ }
+
+ if (reason == RDMA_REMOVE_ABORT) {
+ WARN_ON(!list_empty(&uobj->list));
+ WARN_ON(!uobj->context);
+ uobj->type->type_class->alloc_abort(uobj);
+ }
+
+ uobj->context = NULL;
+
+ /*
+ * For DESTROY the usecnt is held write locked, the caller is expected
+ * to put it unlock and put the object when done with it. Only DESTROY
+ * can remove the IDR handle.
+ */
+ if (reason != RDMA_REMOVE_DESTROY)
+ atomic_set(&uobj->usecnt, 0);
+ else
+ uobj->type->type_class->remove_handle(uobj);
+
+ if (!list_empty(&uobj->list)) {
+ spin_lock_irqsave(&ufile->uobjects_lock, flags);
+ list_del_init(&uobj->list);
+ spin_unlock_irqrestore(&ufile->uobjects_lock, flags);
+
+ /*
+ * Pairs with the get in rdma_alloc_commit_uobject(), could
+ * destroy uobj.
+ */
+ uverbs_uobject_put(uobj);
+ }

- /* lock is either WRITE or DESTROY - should be exclusive */
- return atomic_cmpxchg(&uobj->usecnt, 0, -1) == 0 ? 0 : -EBUSY;
+ /*
+ * When aborting the stack kref remains owned by the core code, and is
+ * not transferred into the type. Pairs with the get in alloc_uobj
+ */
+ if (reason == RDMA_REMOVE_ABORT)
+ uverbs_uobject_put(uobj);
+
+ return 0;
}

-static struct ib_uobject *alloc_uobj(struct ib_ucontext *context,
+/*
+ * This calls uverbs_destroy_uobject() using the RDMA_REMOVE_DESTROY
+ * sequence. It should only be used from command callbacks. On success the
+ * caller must pair this with rdma_lookup_put_uobject(LOOKUP_WRITE). This
+ * version requires the caller to have already obtained an
+ * LOOKUP_DESTROY uobject kref.
+ */
+int uobj_destroy(struct ib_uobject *uobj)
+{
+ struct ib_uverbs_file *ufile = uobj->ufile;
+ int ret;
+
+ down_read(&ufile->hw_destroy_rwsem);
+
+ ret = uverbs_try_lock_object(uobj, UVERBS_LOOKUP_WRITE);
+ if (ret)
+ goto out_unlock;
+
+ ret = uverbs_destroy_uobject(uobj, RDMA_REMOVE_DESTROY);
+ if (ret) {
+ atomic_set(&uobj->usecnt, 0);
+ goto out_unlock;
+ }
+
+out_unlock:
+ up_read(&ufile->hw_destroy_rwsem);
+ return ret;
+}
+
+/*
+ * uobj_get_destroy destroys the HW object and returns a handle to the uobj
+ * with a NULL object pointer. The caller must pair this with
+ * uverbs_put_destroy.
+ */
+struct ib_uobject *__uobj_get_destroy(const struct uverbs_obj_type *type,
+ u32 id, struct ib_uverbs_file *ufile)
+{
+ struct ib_uobject *uobj;
+ int ret;
+
+ uobj = rdma_lookup_get_uobject(type, ufile, id, UVERBS_LOOKUP_DESTROY);
+ if (IS_ERR(uobj))
+ return uobj;
+
+ ret = uobj_destroy(uobj);
+ if (ret) {
+ rdma_lookup_put_uobject(uobj, UVERBS_LOOKUP_DESTROY);
+ return ERR_PTR(ret);
+ }
+
+ return uobj;
+}
+
+/*
+ * Does both uobj_get_destroy() and uobj_put_destroy(). Returns success_res
+ * on success (negative errno on failure). For use by callers that do not need
+ * the uobj.
+ */
+int __uobj_perform_destroy(const struct uverbs_obj_type *type, u32 id,
+ struct ib_uverbs_file *ufile, int success_res)
+{
+ struct ib_uobject *uobj;
+
+ uobj = __uobj_get_destroy(type, id, ufile);
+ if (IS_ERR(uobj))
+ return PTR_ERR(uobj);
+
+ /*
+ * FIXME: After destroy this is not safe. We no longer hold the rwsem
+ * so disassociation could have completed and unloaded the module that
+ * backs the uobj->type pointer.
+ */
+ rdma_lookup_put_uobject(uobj, UVERBS_LOOKUP_WRITE);
+ return success_res;
+}
+
+/* alloc_uobj must be undone by uverbs_destroy_uobject() */
+static struct ib_uobject *alloc_uobj(struct ib_uverbs_file *ufile,
const struct uverbs_obj_type *type)
{
- struct ib_uobject *uobj = kzalloc(type->obj_size, GFP_KERNEL);
+ struct ib_uobject *uobj;
+ struct ib_ucontext *ucontext;
+
+ ucontext = ib_uverbs_get_ucontext(ufile);
+ if (IS_ERR(ucontext))
+ return ERR_CAST(ucontext);

+ uobj = kzalloc(type->obj_size, GFP_KERNEL);
if (!uobj)
return ERR_PTR(-ENOMEM);
/*
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