linux-kernel - Re: [PATCH 7/9] aio: add delayed cancel support

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Date:   Wed, 21 Mar 2018 10:18:42 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     viro@...iv.linux.org.uk, Avi Kivity <avi@...lladb.com>,
        linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/9] aio: add delayed cancel support

On Wed, Mar 21, 2018 at 08:32:30AM +0100, Christoph Hellwig wrote:
> The upcoming aio poll support would like to be able to complete the
> iocb inline from the cancellation context, but that would cause
> a lock order reversal.  Add support for optionally moving the cancelation
> outside the context lock to avoid this reversal.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> Acked-by: Jeff Moyer <jmoyer@...hat.com>
> ---
>  fs/aio.c | 49 ++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 38 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/aio.c b/fs/aio.c
> index 0b6394b4e528..9d7d6e4cde87 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -170,6 +170,10 @@ struct aio_kiocb {
>  	struct list_head	ki_list;	/* the aio core uses this
>  						 * for cancellation */
>  
> +	unsigned int		flags;		/* protected by ctx->ctx_lock */
> +#define AIO_IOCB_DELAYED_CANCEL	(1 << 0)
> +#define AIO_IOCB_CANCELLED	(1 << 1)

BIT(0) and BIT(1)?

Anyway, not a big deal...

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>