netdev - Re: [PATCH 28/32] aio: simplify cancellation

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Message-ID: <x49a7xl49bw.fsf@segfault.boston.devel.redhat.com>
Date:   Wed, 10 Jan 2018 17:50:43 -0500
From:   Jeff Moyer <jmoyer@...hat.com>
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,
        netdev@...r.kernel.org, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 28/32] aio: simplify cancellation

Christoph Hellwig <hch@....de> writes:

> With the current aio code there is no need for the magic KIOCB_CANCELLED
> value, as a cancelation just kicks the driver to queue the completion
> ASAP, with all actual completion handling done in another thread. Given
> that both the completion path and cancelation take the context lock there
> is no need for magic cmpxchg loops either.

The cmpxchg was made unnecessary when the complementary xchg was removed
in commit bec68faaf ("aio: io_cancel() no longer returns the io_event").
There was no longer a need to ensure only the completion path or the
cancellation path delivered the completion event.  Now, the completion
is always delivered via aio_complete.

So yeah, we can get rid of this.

Acked-by: Jeff Moyer <jmoyer@...hat.com>