Commit e6d5d5dd authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

IB/uverbs: Clarify and revise uverbs_close_fd 



The locking requirements here have changed slightly now that we can rely
on the ib_uverbs_file always existing and containing all the necessary
locking infrastructure.

That means we can get rid of the cleanup_mutex usage (this was protecting
the check on !uboj->context).

Otherwise, follow the same pattern that IDR uses for destroy, acquire
exclusive write access, then call destroy and the undo the 'lookup'.

Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 5671f79b

drivers/infiniband/core/rdma_core.c

+28 −13
Original line number Diff line number Diff line
@@ -650,33 +650,48 @@ EXPORT_SYMBOL(uverbs_idr_class); 


static void _uverbs_close_fd(struct ib_uobject *uobj)

{

	struct ib_uverbs_file *ufile = uobj->ufile;

	int ret;



	mutex_lock(&ufile->cleanup_mutex);

	/*

	 * uobject was already cleaned up, remove_commit_fd_uobject

	 * sets this

	 */

	if (!uobj->context)

		return;



	/* uobject was either already cleaned up or is cleaned up right now anyway */

	if (!uobj->context ||

	    !down_read_trylock(&ufile->cleanup_rwsem))

		goto unlock;

	/*

	 * lookup_get_fd_uobject holds the kref on the struct file any time a

	 * FD uobj is locked, which prevents this release method from being

	 * invoked. Meaning we can always get the write lock here, or we have

	 * a kernel bug. If so dangle the pointers and bail.

	 */

	ret = uverbs_try_lock_object(uobj, true);

	if (WARN(ret, "uverbs_close_fd() racing with lookup_get_fd_uobject()"))

		return;



	ret = _rdma_remove_commit_uobject(uobj, RDMA_REMOVE_CLOSE);

	up_read(&ufile->cleanup_rwsem);

	if (ret)

		pr_warn("uverbs: unable to clean up uobject file in uverbs_close_fd.\n");

unlock:

	mutex_unlock(&ufile->cleanup_mutex);

		pr_warn("Unable to clean up uobject file in %s\n", __func__);



	atomic_set(&uobj->usecnt, 0);

}



void uverbs_close_fd(struct file *f)

{

	struct ib_uobject *uobj = f->private_data;

	struct kref *uverbs_file_ref = &uobj->ufile->ref;

	struct ib_uverbs_file *ufile = uobj->ufile;



	if (down_read_trylock(&ufile->cleanup_rwsem)) {

		_uverbs_close_fd(uobj);

		up_read(&ufile->cleanup_rwsem);

	}



	uobj->object = NULL;

	/* Matches the get in alloc_begin_fd_uobject */

	kref_put(&ufile->ref, ib_uverbs_release_file);



	/* Pairs with filp->private_data in alloc_begin_fd_uobject */

	uverbs_uobject_put(uobj);

	kref_put(uverbs_file_ref, ib_uverbs_release_file);

}



static int __uverbs_cleanup_ufile(struct ib_uverbs_file *ufile,

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