aio: io_cancel() no longer returns the io_event

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.

Also tweak the refcounting in kiocb_cancel() to make more sense.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Zach Brown <zab@redhat.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>

diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index 570c005062ab8a3c75a9da56131ffebfdce118aa..e02c1e04529ed31fd3bf7ad8d4a2b2a224634c06 100644 (file)
--- 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 int 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;
 }
 

diff --git a/fs/aio.c b/fs/aio.c
index 7b470bfbf891a6c3a9edeacceb39260bf427469e..12b37689dd2cbab36cdcd5865ea9d94017c8717c 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -358,8 +358,7 @@ 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;
@@ -381,12 +380,10 @@ 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;
 }
@@ -408,7 +405,6 @@ static void free_ioctx(struct work_struct *work)
 {
        struct kioctx *ctx = container_of(work, struct kioctx, free_work);
        struct aio_ring *ring;
-       struct io_event res;
        struct kiocb *req;
        unsigned cpu, head, avail;
 
@@ -419,7 +415,7 @@ static void free_ioctx(struct work_struct *work)
                                       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);
@@ -795,21 +791,6 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
                spin_unlock_irqrestore(&ctx->ctx_lock, flags);
        }
 
-       /*
-        * cancelled requests don't get events, userland was given one
-        * when the event got cancelled.
-        */
-       if (unlikely(xchg(&iocb->ki_cancel,
-                         KIOCB_CANCELLED) == KIOCB_CANCELLED)) {
-               /*
-                * Can't use the percpu reqs_available here - could race with
-                * free_ioctx()
-                */
-               atomic_inc(&ctx->reqs_available);
-               /* Still need the wake_up in case free_ioctx is waiting */
-               goto put_rq;
-       }
-
        /*
         * Add a completion event to the ring buffer. Must be done holding
         * ctx->completion_lock to prevent other code from messing with the tail
@@ -862,7 +843,6 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
        if (iocb->ki_eventfd != NULL)
                eventfd_signal(iocb->ki_eventfd, 1);
 
-put_rq:
        /* everything turned out well, dispose of the aiocb. */
        aio_put_req(iocb);
 
@@ -1439,7 +1419,6 @@ 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;
@@ -1457,18 +1436,19 @@ 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;
        }
 
        percpu_ref_put(&ctx->users);

diff --git a/include/linux/aio.h b/include/linux/aio.h
index 1bdf965339f9bef4222a5bc739efc0b23807e35e..8c8dd1d84d2eeec4614c8d319d9f820ca5c2751b 100644 (file)
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -27,7 +27,7 @@ struct kiocb;
  */
 #define KIOCB_CANCELLED                ((void *) (~0ULL))
 
-typedef int (kiocb_cancel_fn)(struct kiocb *, struct io_event *);
+typedef int (kiocb_cancel_fn)(struct kiocb *);
 
 struct kiocb {
        atomic_t                ki_users;