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SubjectRe: [PATCH 3/8] aio_poll(): sanitize the logics after vfs_poll(), get rid of leak on error
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+	if (async && !apt.error)  --->may be this should be if (!async && !apt.error) ?

On 2019/3/7 8:03, Al Viro wrote:
> From: Al Viro <viro@zeniv.linux.org.uk>
>
> We want iocb_put() happening on errors, to balance the extra reference
> we'd taken. As it is, we end up with a leak. The rules should be
> * error: iocb_put() to deal with the extra ref, return error,
> let the caller do another iocb_put().
> * async: iocb_put() to deal with the extra ref, return 0.
> * no error, event present immediately: aio_poll_complete() to
> report it, iocb_put() to deal with the extra ref, return 0.
>
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
> fs/aio.c | 25 +++++++++++--------------
> 1 file changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 3a8b894378e0..22b288997441 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1724,6 +1724,7 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
> struct kioctx *ctx = aiocb->ki_ctx;
> struct poll_iocb *req = &aiocb->poll;
> struct aio_poll_table apt;
> + bool async = false;
> __poll_t mask;
>
> /* reject any unknown events outside the normal event mask. */
> @@ -1760,30 +1761,26 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
>
> spin_lock_irq(&ctx->ctx_lock);
> spin_lock(&req->head->lock);
> - if (req->woken) {
> - /* wake_up context handles the rest */
> - mask = 0;
> + if (req->woken) { /* already taken up by aio_poll_wake() */
> + async = true;
> apt.error = 0;
> - } else if (mask || apt.error) {
> - /* if we get an error or a mask we are done */
> - WARN_ON_ONCE(list_empty(&req->wait.entry));
> - list_del_init(&req->wait.entry);
> - } else {
> - /* actually waiting for an event */
> + } else if (!mask && !apt.error) { /* actually waiting for an event */
> list_add_tail(&aiocb->ki_list, &ctx->active_reqs);
> aiocb->ki_cancel = aio_poll_cancel;
> + async = true;
> + } else { /* if we get an error or a mask we are done */
> + WARN_ON_ONCE(list_empty(&req->wait.entry));
> + list_del_init(&req->wait.entry);
> + /* no wakeup in the future either; aiocb is ours to dispose of */
> }
> spin_unlock(&req->head->lock);
> spin_unlock_irq(&ctx->ctx_lock);
>
> out:
> - if (unlikely(apt.error))
> - return apt.error;
> -
> - if (mask)
> + if (async && !apt.error)
> aio_poll_complete(aiocb, mask);
> iocb_put(aiocb);
> - return 0;
> + return apt.error;
> }
>
> static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
>

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