Commit 3d48749d authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

block: ioc_task_link() can't fail 



ioc_task_link() is used to share %current's ioc on clone.  If
%current->io_context is set, %current is guaranteed to have refcount
on the ioc and, thus, ioc_task_link() can't fail.

Replace error checking in ioc_task_link() with WARN_ON_ONCE() and make
it just increment refcount and nr_tasks.

-v2: Description typo fix (Vivek).

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 24acfc34

include/linux/iocontext.h

+5 −11
Original line number Diff line number Diff line
@@ -120,18 +120,12 @@ struct io_context { 
	struct work_struct release_work;

};



static inline struct io_context *ioc_task_link(struct io_context *ioc)

static inline void ioc_task_link(struct io_context *ioc)

{

	/*

	 * if ref count is zero, don't allow sharing (ioc is going away, it's

	 * a race).

	 */

	if (ioc && atomic_long_inc_not_zero(&ioc->refcount)) {

	WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0);

	WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);

	atomic_long_inc(&ioc->refcount);

	atomic_inc(&ioc->nr_tasks);

		return ioc;

	}



	return NULL;

}



struct task_struct;

kernel/fork.c

+2 −3
Original line number Diff line number Diff line
@@ -901,9 +901,8 @@ static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 
	 * Share io context with parent, if CLONE_IO is set

	 */

	if (clone_flags & CLONE_IO) {

		tsk->io_context = ioc_task_link(ioc);

		if (unlikely(!tsk->io_context))

			return -ENOMEM;

		ioc_task_link(ioc);

		tsk->io_context = ioc;

	} else if (ioprio_valid(ioc->ioprio)) {

		new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);

		if (unlikely(!new_ioc))

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