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IB/uverbs: Allow RDMA_REMOVE_DESTROY to work concurrently with disassociate

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After all the recent structural changes this is now straightfoward, hoist
the hw_destroy_rwsem up out of rdma_destroy_explicit and wrap it around
the uobject write lock as well as the destroy.

This is necessary as obtaining a write lock concurrently with
uverbs_destroy_ufile_hw() will cause malfunction.

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

This requires introducing a new lookup mode, UVERBS_LOOKUP_DESTROY as the
IOCTL interface needs to hold an unlocked kref until all command
verification is completed.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2018-07-25 21:40:14 -06:00
parent 9867f5c669
commit 7452a3c745
4 changed files with 63 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

71
drivers/infiniband/core/rdma_core.c
View File

@ -127,8 +127,10 @@ static int uverbs_try_lock_object(struct ib_uobject *uobj,
return __atomic_add_unless(&uobj->usecnt, 1, -1) == -1 ?
-EBUSY : 0;
case UVERBS_LOOKUP_WRITE:
/* lock is either WRITE or DESTROY - should be exclusive */
/* lock is exclusive */
return atomic_cmpxchg(&uobj->usecnt, 0, -1) == 0 ? 0 : -EBUSY;
case UVERBS_LOOKUP_DESTROY:
return 0;
}
return 0;
}
@ -144,6 +146,8 @@ static void assert_uverbs_usecnt(struct ib_uobject *uobj,
case UVERBS_LOOKUP_WRITE:
WARN_ON(atomic_read(&uobj->usecnt) != -1);
break;
case UVERBS_LOOKUP_DESTROY:
break;
}
#endif
}
@ -227,6 +231,35 @@ static int uverbs_destroy_uobject(struct ib_uobject *uobj,
return 0;
}
/*
* 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
@ -238,13 +271,13 @@ struct ib_uobject *__uobj_get_destroy(const struct uverbs_obj_type *type,
struct ib_uobject *uobj;
int ret;
uobj = rdma_lookup_get_uobject(type, ufile, id, UVERBS_LOOKUP_WRITE);
uobj = rdma_lookup_get_uobject(type, ufile, id, UVERBS_LOOKUP_DESTROY);
if (IS_ERR(uobj))
return uobj;
ret = rdma_explicit_destroy(uobj);
ret = uobj_destroy(uobj);
if (ret) {
rdma_lookup_put_uobject(uobj, UVERBS_LOOKUP_WRITE);
rdma_lookup_put_uobject(uobj, UVERBS_LOOKUP_DESTROY);
return ERR_PTR(ret);
}
@ -265,6 +298,11 @@ int __uobj_perform_destroy(const struct uverbs_obj_type *type, u32 id,
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;
}
@ -534,23 +572,6 @@ static int __must_check remove_commit_fd_uobject(struct ib_uobject *uobj,
return 0;
}
int rdma_explicit_destroy(struct ib_uobject *uobject)
{
int ret;
struct ib_uverbs_file *ufile = uobject->ufile;
/* 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 removing an uobject\n");
return 0;
}
ret = uverbs_destroy_uobject(uobject, RDMA_REMOVE_DESTROY);
up_read(&ufile->hw_destroy_rwsem);
return ret;
}
static int alloc_commit_idr_uobject(struct ib_uobject *uobj)
{
struct ib_uverbs_file *ufile = uobj->ufile;
@ -686,6 +707,8 @@ void rdma_lookup_put_uobject(struct ib_uobject *uobj,
case UVERBS_LOOKUP_WRITE:
atomic_set(&uobj->usecnt, 0);
break;
case UVERBS_LOOKUP_DESTROY:
break;
}
/* Pairs with the kref obtained by type->lookup_get */
@ -911,6 +934,9 @@ uverbs_get_uobject_from_file(const struct uverbs_obj_type *type_attrs,
return rdma_lookup_get_uobject(type_attrs, ufile, id,
UVERBS_LOOKUP_READ);
case UVERBS_ACCESS_DESTROY:
/* Actual destruction is done inside uverbs_handle_method */
return rdma_lookup_get_uobject(type_attrs, ufile, id,
UVERBS_LOOKUP_DESTROY);
case UVERBS_ACCESS_WRITE:
return rdma_lookup_get_uobject(type_attrs, ufile, id,
UVERBS_LOOKUP_WRITE);
@ -942,7 +968,8 @@ int uverbs_finalize_object(struct ib_uobject *uobj,
rdma_lookup_put_uobject(uobj, UVERBS_LOOKUP_WRITE);
break;
case UVERBS_ACCESS_DESTROY:
rdma_lookup_put_uobject(uobj, UVERBS_LOOKUP_WRITE);
if (uobj)
rdma_lookup_put_uobject(uobj, UVERBS_LOOKUP_DESTROY);
break;
case UVERBS_ACCESS_NEW:
if (commit)

2
drivers/infiniband/core/rdma_core.h
View File

@ -52,6 +52,8 @@ const struct uverbs_method_spec *uverbs_get_method(const struct uverbs_object_sp
void uverbs_destroy_ufile_hw(struct ib_uverbs_file *ufile,
enum rdma_remove_reason reason);
int uobj_destroy(struct ib_uobject *uobj);
/*
* uverbs_uobject_get is called in order to increase the reference count on
* an uobject. This is useful when a handler wants to keep the uobject's memory

7
drivers/infiniband/core/uverbs_ioctl.c
View File

@ -349,13 +349,18 @@ static int uverbs_handle_method(struct ib_uverbs_attr __user *uattr_ptr,
* not get to manipulate the HW objects.
*/
if (destroy_attr) {
ret = rdma_explicit_destroy(destroy_attr->uobject);
ret = uobj_destroy(destroy_attr->uobject);
if (ret)
goto cleanup;
}
ret = method_spec->handler(ibdev, ufile, attr_bundle);
if (destroy_attr) {
uobj_put_destroy(destroy_attr->uobject);
destroy_attr->uobject = NULL;
}
cleanup:
finalize_ret = uverbs_finalize_attrs(attr_bundle,
method_spec->attr_buckets,

7
include/rdma/uverbs_types.h
View File

@ -41,6 +41,12 @@ struct uverbs_obj_type;
enum rdma_lookup_mode {
UVERBS_LOOKUP_READ,
UVERBS_LOOKUP_WRITE,
/*
* Destroy is like LOOKUP_WRITE, except that the uobject is not
* locked. uobj_destroy is used to convert a LOOKUP_DESTROY lock into
* a LOOKUP_WRITE lock.
*/
UVERBS_LOOKUP_DESTROY,
};
/*
@ -129,7 +135,6 @@ struct ib_uobject *rdma_alloc_begin_uobject(const struct uverbs_obj_type *type,
struct ib_uverbs_file *ufile);
void rdma_alloc_abort_uobject(struct ib_uobject *uobj);
int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj);
int rdma_explicit_destroy(struct ib_uobject *uobject);
struct uverbs_obj_fd_type {
/*