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Commit aba94548 authored by Jason Gunthorpe's avatar Jason Gunthorpe
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IB/uverbs: Move the FD uobj type struct file allocation to alloc_commit 



Allocating the struct file during alloc_begin creates this strange
asymmetry with IDR, where the FD has two krefs pointing at it during the
pre-commit phase. In particular this makes the abort process for FD very
strange and confusing.

For instance abort currently calls the type's destroy_object twice, and
the fops release once if abort is done. This is very counter intuitive. No
fops should be called until alloc_commit succeeds, and destroy_object
should only ever be called once.

Moving the struct file allocation to the alloc_commit is now simple, as we
already support failure of rdma_alloc_commit_uobject, with all the
required rollback pieces.

This creates an understandable symmetry with IDR and simplifies/fixes the
abort handling for FD types.

Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 2c96eb7d

drivers/infiniband/core/rdma_core.c

+46 −37
Original line number Diff line number Diff line
@@ -328,11 +328,8 @@ static struct ib_uobject *alloc_begin_idr_uobject(const struct uverbs_obj_type * 
static struct ib_uobject *alloc_begin_fd_uobject(const struct uverbs_obj_type *type,

						 struct ib_uverbs_file *ufile)

{

	const struct uverbs_obj_fd_type *fd_type =

		container_of(type, struct uverbs_obj_fd_type, type);

	int new_fd;

	struct ib_uobject *uobj;

	struct file *filp;



	new_fd = get_unused_fd_flags(O_CLOEXEC);

	if (new_fd < 0)
@@ -344,28 +341,8 @@ static struct ib_uobject *alloc_begin_fd_uobject(const struct uverbs_obj_type *t 
		return uobj;

	}



	/*

	 * The kref for uobj is moved into filp->private data and put in

	 * uverbs_close_fd(). Once anon_inode_getfile() succeeds

	 * uverbs_close_fd() must be guaranteed to be called from the provided

	 * fops release callback. We piggyback our kref of uobj on the stack

	 * with the lifetime of the struct file.

	 */

	filp = anon_inode_getfile(fd_type->name,

				  fd_type->fops,

				  uobj,

				  fd_type->flags);

	if (IS_ERR(filp)) {

		put_unused_fd(new_fd);

		uverbs_uobject_put(uobj);

		return (void *)filp;

	}



	uobj->id = new_fd;

	uobj->object = filp;

	uobj->ufile = ufile;

	/* Matching put will be done in uverbs_close_fd() */

	kref_get(&ufile->ref);



	return uobj;

}
@@ -407,12 +384,10 @@ static int __must_check remove_commit_idr_uobject(struct ib_uobject *uobj, 


static void alloc_abort_fd_uobject(struct ib_uobject *uobj)

{

	struct file *filp = uobj->object;

	int id = uobj->id;

	put_unused_fd(uobj->id);



	/* Unsuccessful NEW */

	fput(filp);

	put_unused_fd(id);

	/* Pairs with the kref from alloc_begin_idr_uobject */

	uverbs_uobject_put(uobj);

}



static int __must_check remove_commit_fd_uobject(struct ib_uobject *uobj,
@@ -500,7 +475,7 @@ int rdma_explicit_destroy(struct ib_uobject *uobject) 
	return ret;

}



static void alloc_commit_idr_uobject(struct ib_uobject *uobj)

static int alloc_commit_idr_uobject(struct ib_uobject *uobj)

{

	struct ib_uverbs_file *ufile = uobj->ufile;
@@ -514,11 +489,34 @@ static void alloc_commit_idr_uobject(struct ib_uobject *uobj) 
	 */

	WARN_ON(idr_replace(&ufile->idr, uobj, uobj->id));

	spin_unlock(&ufile->idr_lock);



	return 0;

}



static void alloc_commit_fd_uobject(struct ib_uobject *uobj)

static int alloc_commit_fd_uobject(struct ib_uobject *uobj)

{

	const struct uverbs_obj_fd_type *fd_type =

		container_of(uobj->type, struct uverbs_obj_fd_type, type);

	int fd = uobj->id;

	struct file *filp;



	/*

	 * The kref for uobj is moved into filp->private data and put in

	 * uverbs_close_fd(). Once alloc_commit() succeeds uverbs_close_fd()

	 * must be guaranteed to be called from the provided fops release

	 * callback.

	 */

	filp = anon_inode_getfile(fd_type->name,

				  fd_type->fops,

				  uobj,

				  fd_type->flags);

	if (IS_ERR(filp))

		return PTR_ERR(filp);



	uobj->object = filp;



	/* Matching put will be done in uverbs_close_fd() */

	kref_get(&uobj->ufile->ref);



	/* This shouldn't be used anymore. Use the file object instead */

	uobj->id = 0;
@@ -527,7 +525,9 @@ static void alloc_commit_fd_uobject(struct ib_uobject *uobj) 
	 * NOTE: Once we install the file we loose ownership of our kref on

	 * uobj. It will be put by uverbs_close_fd()

	 */

	fd_install(fd, uobj->object);

	fd_install(fd, filp);



	return 0;

}



/*
@@ -538,11 +538,10 @@ static void alloc_commit_fd_uobject(struct ib_uobject *uobj) 
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)) {

		int ret;



		WARN(true, "ib_uverbs: Cleanup is running while allocating an uobject\n");

		ret = uobj->type->type_class->remove_commit(uobj,

							    RDMA_REMOVE_DURING_CLEANUP);
@@ -552,9 +551,18 @@ int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj) 
		return ret;

	}



	/* matches atomic_set(-1) in alloc_uobj */

	assert_uverbs_usecnt(uobj, true);

	atomic_set(&uobj->usecnt, 0);



	/* alloc_commit consumes the uobj kref */

	ret = uobj->type->type_class->alloc_commit(uobj);

	if (ret) {

		if (uobj->type->type_class->remove_commit(

			    uobj, RDMA_REMOVE_DURING_CLEANUP))

			pr_warn("ib_uverbs: cleanup of idr object %d failed\n",

				uobj->id);

		up_read(&ufile->hw_destroy_rwsem);

		return ret;

	}



	/* kref is held so long as the uobj is on the uobj list. */

	uverbs_uobject_get(uobj);
@@ -562,8 +570,9 @@ int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj) 
	list_add(&uobj->list, &ufile->uobjects);

	spin_unlock_irq(&ufile->uobjects_lock);



	/* alloc_commit consumes the uobj kref */

	uobj->type->type_class->alloc_commit(uobj);

	/* matches atomic_set(-1) in alloc_uobj */

	atomic_set(&uobj->usecnt, 0);



	up_read(&ufile->hw_destroy_rwsem);



	return 0;

include/rdma/uverbs_types.h

+1 −1
Original line number Diff line number Diff line
@@ -73,7 +73,7 @@ struct uverbs_obj_type_class { 
	 */

	struct ib_uobject *(*alloc_begin)(const struct uverbs_obj_type *type,

					  struct ib_uverbs_file *ufile);

	void (*alloc_commit)(struct ib_uobject *uobj);

	int (*alloc_commit)(struct ib_uobject *uobj);

	void (*alloc_abort)(struct ib_uobject *uobj);



	struct ib_uobject *(*lookup_get)(const struct uverbs_obj_type *type,