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| author | Tejun Heo <tj@kernel.org> | 2012-03-05 13:15:25 -0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2012-03-06 21:27:24 +0100 |
| commit | 3d48749d93a3dce732dd30a14002ab90ec4355f3 (patch) | |
| tree | 50ce414ec87e590493476cf644092439c5f337fd | |
| parent | 24acfc34fba0b4f62ef9d5c2616eb0faa802b606 (diff) | |
| download | linux-3d48749d93a3dce732dd30a14002ab90ec4355f3.tar.gz linux-3d48749d93a3dce732dd30a14002ab90ec4355f3.tar.bz2 linux-3d48749d93a3dce732dd30a14002ab90ec4355f3.zip | |
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>
| -rw-r--r-- | include/linux/iocontext.h | 16 | ||||
| -rw-r--r-- | kernel/fork.c | 5 |
2 files changed, 7 insertions, 14 deletions
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h index 1a3018063034..81a8870ac224 100644 --- a/include/linux/iocontext.h +++ b/include/linux/iocontext.h @@ -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; 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)) |