From: Christoph Hellwig <hch@infradead.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Subject: Re: [PATCH V2 2/2] ublk_drv: make sure that correct flags(features) returned to userspace
Date: Fri, 22 Jul 2022 01:09:00 -0700 [thread overview]
Message-ID: <YtpbHPJDgwi3gMho@infradead.org> (raw)
In-Reply-To: <YtpSCX5ZC3cnWakM@T590>
On Fri, Jul 22, 2022 at 03:30:17PM +0800, Ming Lei wrote:
> > > +enum ublk_flag_bits {
> > > + __UBLK_F_SUPPORT_ZERO_COPY,
> > > + __UBLK_F_URING_CMD_COMP_IN_TASK,
> > > + __UBLK_F_NR_BITS,
> > > +};
> >
> > Please make these #defines so that userspace can detect if they
> > exist in a header using #ifdef.
>
> userspace is supposed to only use UBLK_F_* instead of __UBLK_F_*, one
> benefit of using enum is that UBLK_F_NR_BITS can be figured out
> automatically, otherwise how can we figure out the max bits?
Oh, indeed. But I don't think the automatic max index is really
that useful. Just use a manually maintained in-kernel UBLK_F_ALL,
that is just as little overhead to maintain as the extra enum.
And if you forget to add a flag that code will never see it as it
gets cleared before the device is added.
next prev parent reply other threads:[~2022-07-22 8:09 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-22 5:09 [PATCH V2 0/2] ublk_drv: make sure that correct flags(features) returned to userspace Ming Lei
2022-07-22 5:09 ` [PATCH V2 1/2] ublk_drv: fix error handling of ublk_add_dev Ming Lei
2022-07-22 5:48 ` Christoph Hellwig
2022-07-22 6:17 ` Christoph Hellwig
2022-07-22 7:35 ` Ziyang Zhang
2022-07-22 5:58 ` Ziyang Zhang
2022-07-22 5:09 ` [PATCH V2 2/2] ublk_drv: make sure that correct flags(features) returned to userspace Ming Lei
2022-07-22 5:50 ` Christoph Hellwig
2022-07-22 7:30 ` Ming Lei
2022-07-22 8:09 ` Christoph Hellwig [this message]
2022-07-22 6:00 ` Ziyang Zhang
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