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Date: Thu, 28 Feb 2013 16:40:56 -0500
From: Benjamin LaHaise <bcrl@...ck.org>
To: Kent Overstreet <koverstreet@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-aio@...ck.org, tytso@....edu, axboe@...nel.dk,
zab@...hat.com, anatol@...gle.com
Subject: Re: [PATCH 1/4] aio: io_cancel() no longer returns the io_event
On Thu, Feb 28, 2013 at 12:35:38PM -0800, Kent Overstreet wrote:
> Originally, io_event() was documented to return the io_event if
> cancellation succeeded - the io_event wouldn't be delivered via the ring
> buffer like it normally would.
>
> But this isn't what the implementation was actually doing; the only
> driver implementing cancellation, the usb gadget code, never returned an
> io_event in its cancel function. And aio_complete() was recently changed
> to no longer suppress event delivery if the kiocb had been cancelled.
>
> This gets rid of the unused io_event argument to kiocb_cancel() and
> kiocb->ki_cancel(), and changes io_cancel() to return -EINPROGRESS if
> kiocb->ki_cancel() returned success.
...
> diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
> index b540a1d..fd1bf4a 100644
> --- a/drivers/usb/gadget/inode.c
> +++ b/drivers/usb/gadget/inode.c
> @@ -524,7 +524,7 @@ struct kiocb_priv {
> unsigned actual;
> };
>
> -static int ep_aio_cancel(struct kiocb *iocb, struct io_event *e)
> +static void ep_aio_cancel(struct kiocb *iocb)
> {
> struct kiocb_priv *priv = iocb->private;
> struct ep_data *epdata;
> @@ -540,7 +540,6 @@ static int ep_aio_cancel(struct kiocb *iocb, struct io_event *e)
> // spin_unlock(&epdata->dev->lock);
> local_irq_enable();
>
> - aio_put_req(iocb);
> return value;
> }
>
You seem to have removed the return value from ki_cancel in the gadget code,
so this won't compile. I think this is wrong and an unnecessary restriction
As such, I'm NAKing this patch. Please leave the return value from the
ki_cancel function present so we can know if the cancel actually succeeded.
-ben
> diff --git a/fs/aio.c b/fs/aio.c
> index a86ffd0..4b9bfb5 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -256,8 +256,7 @@ void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel)
> }
> EXPORT_SYMBOL(kiocb_set_cancel_fn);
>
> -static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb,
> - struct io_event *res)
> +static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb)
> {
> kiocb_cancel_fn *old, *cancel;
> int ret = -EINVAL;
> @@ -279,12 +278,10 @@ static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb,
> atomic_inc(&kiocb->ki_users);
> spin_unlock_irq(&ctx->ctx_lock);
>
> - memset(res, 0, sizeof(*res));
> - res->obj = (u64)(unsigned long)kiocb->ki_obj.user;
> - res->data = kiocb->ki_user_data;
> - ret = cancel(kiocb, res);
> + ret = cancel(kiocb);
>
> spin_lock_irq(&ctx->ctx_lock);
> + aio_put_req(kiocb);
>
> return ret;
> }
> @@ -305,7 +302,6 @@ static void free_ioctx_rcu(struct rcu_head *head)
> static void free_ioctx(struct kioctx *ctx)
> {
> struct aio_ring *ring;
> - struct io_event res;
> struct kiocb *req;
> unsigned cpu, head, avail;
>
> @@ -316,7 +312,7 @@ static void free_ioctx(struct kioctx *ctx)
> struct kiocb, ki_list);
>
> list_del_init(&req->ki_list);
> - kiocb_cancel(ctx, req, &res);
> + kiocb_cancel(ctx, req);
> }
>
> spin_unlock_irq(&ctx->ctx_lock);
> @@ -1351,7 +1347,6 @@ static struct kiocb *lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb,
> SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
> struct io_event __user *, result)
> {
> - struct io_event res;
> struct kioctx *ctx;
> struct kiocb *kiocb;
> u32 key;
> @@ -1369,18 +1364,19 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
>
> kiocb = lookup_kiocb(ctx, iocb, key);
> if (kiocb)
> - ret = kiocb_cancel(ctx, kiocb, &res);
> + ret = kiocb_cancel(ctx, kiocb);
> else
> ret = -EINVAL;
>
> spin_unlock_irq(&ctx->ctx_lock);
>
> if (!ret) {
> - /* Cancellation succeeded -- copy the result
> - * into the user's buffer.
> + /*
> + * The result argument is no longer used - the io_event is
> + * always delivered via the ring buffer. -EINPROGRESS indicates
> + * cancellation is progress:
> */
> - if (copy_to_user(result, &res, sizeof(res)))
> - ret = -EFAULT;
> + ret = -EINPROGRESS;
> }
>
> put_ioctx(ctx);
> diff --git a/include/linux/aio.h b/include/linux/aio.h
> index 93892bf..7340f77 100644
> --- a/include/linux/aio.h
> +++ b/include/linux/aio.h
> @@ -28,7 +28,7 @@ struct batch_complete;
> */
> #define KIOCB_CANCELLED ((void *) (~0ULL))
>
> -typedef int (kiocb_cancel_fn)(struct kiocb *, struct io_event *);
> +typedef int (kiocb_cancel_fn)(struct kiocb *);
>
> struct kiocb {
> struct rb_node ki_node;
> --
> 1.7.12
--
"Thought is the essence of where you are now."
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