IB/uverbs: Allow uobject allocation to work concurrently with disassociate

After all the recent structural changes this is now straightforward, hold
the hw_destroy_rwsem across the entire uobject creation. We already take
this semaphore on the success path, so holding it a bit longer is not
going to change the performance.

After this change none of the create callbacks require the
disassociate_srcu lock to be correct.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c
index 81d668a..95a8110 100644 (file)
--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@ -153,9 +153,8 @@ static void assert_uverbs_usecnt(struct ib_uobject *uobj,
 }
 
 /*
- * This must be called with the hw_destroy_rwsem locked (except for
- * RDMA_REMOVE_ABORT) for read or write, also The uobject itself must be
- * locked for write.
+ * 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.
  *
@@ -177,6 +176,7 @@ static int uverbs_destroy_uobject(struct ib_uobject *uobj,
        unsigned long flags;
        int ret;
 
+       lockdep_assert_held(&ufile->hw_destroy_rwsem);
        assert_uverbs_usecnt(uobj, UVERBS_LOOKUP_WRITE);
 
        if (uobj->object) {
@@ -515,7 +515,22 @@ static struct ib_uobject *alloc_begin_fd_uobject(const struct uverbs_obj_type *t
 struct ib_uobject *rdma_alloc_begin_uobject(const struct uverbs_obj_type *type,
                                            struct ib_uverbs_file *ufile)
 {
-       return type->type_class->alloc_begin(type, ufile);
+       struct ib_uobject *ret;
+
+       /*
+        * The hw_destroy_rwsem is held across the entire object creation and
+        * released during rdma_alloc_commit_uobject or
+        * rdma_alloc_abort_uobject
+        */
+       if (!down_read_trylock(&ufile->hw_destroy_rwsem))
+               return ERR_PTR(-EIO);
+
+       ret = type->type_class->alloc_begin(type, ufile);
+       if (IS_ERR(ret)) {
+               up_read(&ufile->hw_destroy_rwsem);
+               return ret;
+       }
+       return ret;
 }
 
 static void alloc_abort_idr_uobject(struct ib_uobject *uobj)
@@ -637,17 +652,11 @@ int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj)
        struct ib_uverbs_file *ufile = uobj->ufile;
        int ret;
 
-       /* Cleanup is running. Calling this should have been impossible */
-       if (!down_read_trylock(&ufile->hw_destroy_rwsem)) {
-               WARN(true, "ib_uverbs: Cleanup is running while allocating an uobject\n");
-               uverbs_destroy_uobject(uobj, RDMA_REMOVE_ABORT);
-               return -EINVAL;
-       }
-
        /* alloc_commit consumes the uobj kref */
        ret = uobj->type->type_class->alloc_commit(uobj);
        if (ret) {
                uverbs_destroy_uobject(uobj, RDMA_REMOVE_ABORT);
+               up_read(&ufile->hw_destroy_rwsem);
                return ret;
        }
 
@@ -660,6 +669,7 @@ int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj)
        /* matches atomic_set(-1) in alloc_uobj */
        atomic_set(&uobj->usecnt, 0);
 
+       /* Matches the down_read in rdma_alloc_begin_uobject */
        up_read(&ufile->hw_destroy_rwsem);
 
        return 0;
@@ -671,8 +681,13 @@ int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj)
  */
 void rdma_alloc_abort_uobject(struct ib_uobject *uobj)
 {
+       struct ib_uverbs_file *ufile = uobj->ufile;
+
        uobj->object = NULL;
        uverbs_destroy_uobject(uobj, RDMA_REMOVE_ABORT);
+
+       /* Matches the down_read in rdma_alloc_begin_uobject */
+       up_read(&ufile->hw_destroy_rwsem);
 }
 
 static void lookup_put_idr_uobject(struct ib_uobject *uobj,