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block: ioc_task_link() can't fail

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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>
This commit is contained in:
Tejun Heo 2012-03-05 13:15:25 -08:00 committed by Jens Axboe
parent 24acfc34fb
commit 3d48749d93
2 changed files with 7 additions and 14 deletions
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16
include/linux/iocontext.h
View File

@ -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)) {
atomic_inc(&ioc->nr_tasks);
return ioc;
}
return NULL;
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);
}
struct task_struct;

5
kernel/fork.c
View File

@ -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))