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Message-ID: <20121129005829.GA15094@google.com>
Date: Wed, 28 Nov 2012 16:58:29 -0800
From: Kent Overstreet <koverstreet@...gle.com>
To: Zach Brown <zab@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-aio@...ck.org,
linux-fsdevel@...r.kernel.org, bcrl@...ck.org, jmoyer@...hat.com,
axboe@...nel.dk, viro@...iv.linux.org.uk
Subject: Re: [PATCH 07/25] aio: kiocb_cancel()
On Wed, Nov 28, 2012 at 04:07:53PM -0800, Zach Brown wrote:
> On Wed, Nov 28, 2012 at 08:43:31AM -0800, Kent Overstreet wrote:
> > Minor refactoring, to get rid of some duplicated code
>
> A minor nit:
>
> > spin_lock_irq(&ctx->ctx_lock);
> > - ret = -EAGAIN;
> > +
> > kiocb = lookup_kiocb(ctx, iocb, key);
> > - if (kiocb && kiocb->ki_cancel) {
> > - cancel = kiocb->ki_cancel;
> > - kiocb->ki_users ++;
> > - kiocbSetCancelled(kiocb);
> > - } else
> > - cancel = NULL;
> ...
> > - if (NULL != cancel) {
> > - } else
> > - ret = -EINVAL;
>
> In the old code it'd return -EINVAL for a NULL kiocb, despite that
> misleading unused EAGAIN.
Oh damn, that's evil. Hadn't noticed that before.
>
> > + if (kiocb)
> > + ret = kiocb_cancel(ctx, kiocb, &res);
> > + else
> > + ret = -EAGAIN;
>
> But now it returns -EAGAIN.
>
> I bet we want to err on the side of caution and maintain behaviour, no
> matter how funky.
Agreed. Fixed patch below:
fatal: Not a git repository (or any of the parent directories): .git
commit 7ad9d0a1914e9563021c0f5f7fc55f20e41999e7
Author: Kent Overstreet <koverstreet@...gle.com>
Date: Wed Nov 28 16:57:48 2012 -0800
aio: kiocb_cancel()
Minor refactoring, to get rid of some duplicated code
Signed-off-by: Kent Overstreet <koverstreet@...gle.com>
diff --git a/fs/aio.c b/fs/aio.c
index 91879d4..786c904 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -217,6 +217,29 @@ static inline void put_ioctx(struct kioctx *kioctx)
__put_ioctx(kioctx);
}
+static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb,
+ struct io_event *res)
+{
+ int (*cancel)(struct kiocb *, struct io_event *);
+ int ret = -EINVAL;
+
+ cancel = kiocb->ki_cancel;
+ kiocbSetCancelled(kiocb);
+ if (cancel) {
+ kiocb->ki_users++;
+ spin_unlock_irq(&ctx->ctx_lock);
+
+ memset(res, 0, sizeof(*res));
+ res->obj = (u64) kiocb->ki_obj.user;
+ res->data = kiocb->ki_user_data;
+ ret = cancel(kiocb, res);
+
+ spin_lock_irq(&ctx->ctx_lock);
+ }
+
+ return ret;
+}
+
/* ioctx_alloc
* Allocates and initializes an ioctx. Returns an ERR_PTR if it failed.
*/
@@ -287,7 +310,6 @@ out_freectx:
*/
static void kill_ctx(struct kioctx *ctx)
{
- int (*cancel)(struct kiocb *, struct io_event *);
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
struct io_event res;
@@ -298,14 +320,8 @@ static void kill_ctx(struct kioctx *ctx)
struct list_head *pos = ctx->active_reqs.next;
struct kiocb *iocb = list_kiocb(pos);
list_del_init(&iocb->ki_list);
- cancel = iocb->ki_cancel;
- kiocbSetCancelled(iocb);
- if (cancel) {
- iocb->ki_users++;
- spin_unlock_irq(&ctx->ctx_lock);
- cancel(iocb, &res);
- spin_lock_irq(&ctx->ctx_lock);
- }
+
+ kiocb_cancel(ctx, iocb, &res);
}
if (!ctx->reqs_active)
@@ -1411,7 +1427,7 @@ 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)
{
- int (*cancel)(struct kiocb *iocb, struct io_event *res);
+ struct io_event res;
struct kioctx *ctx;
struct kiocb *kiocb;
u32 key;
@@ -1426,32 +1442,22 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
return -EINVAL;
spin_lock_irq(&ctx->ctx_lock);
- ret = -EAGAIN;
+
kiocb = lookup_kiocb(ctx, iocb, key);
- if (kiocb && kiocb->ki_cancel) {
- cancel = kiocb->ki_cancel;
- kiocb->ki_users ++;
- kiocbSetCancelled(kiocb);
- } else
- cancel = NULL;
+ if (kiocb)
+ ret = kiocb_cancel(ctx, kiocb, &res);
+ else
+ ret = -EINVAL;
+
spin_unlock_irq(&ctx->ctx_lock);
- if (NULL != cancel) {
- struct io_event tmp;
- pr_debug("calling cancel\n");
- memset(&tmp, 0, sizeof(tmp));
- tmp.obj = (u64)(unsigned long)kiocb->ki_obj.user;
- tmp.data = kiocb->ki_user_data;
- ret = cancel(kiocb, &tmp);
- if (!ret) {
- /* Cancellation succeeded -- copy the result
- * into the user's buffer.
- */
- if (copy_to_user(result, &tmp, sizeof(tmp)))
- ret = -EFAULT;
- }
- } else
- ret = -EINVAL;
+ if (!ret) {
+ /* Cancellation succeeded -- copy the result
+ * into the user's buffer.
+ */
+ if (copy_to_user(result, &res, sizeof(res)))
+ ret = -EFAULT;
+ }
put_ioctx(ctx);
--
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