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: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 3 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index b77fd559c78e..a1b632713e43 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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))