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Date:   Wed, 20 Oct 2021 10:30:23 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: [PATCH] fs: kill unused ret2 argument from iocb->ki_complete()
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On Wed, Oct 20, 2021 at 10:49:07AM -0600, Jens Axboe wrote:
> It's not used for anything, and we're wasting time passing in zeroes
> where we could just ignore it instead. Update all ki_complete users in
> the kernel to drop that last argument.
> 
> The exception is the USB gadget code, which passes in non-zero. But
> since nobody every looks at ret2, it's still pointless.

Yes, the USB gadget passes non-zero, and aio passes that on to
userspace.  So this is an ABI change.  Does it actually matter?
I don't know, but you could CC the relevant maintainers and list
to try to figure that out.