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Date: Thu, 4 May 2017 02:51:34 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Tycho Andersen <tycho@...ker.com>
Cc: Tejun Heo <tj@...nel.org>, Juerg Haefliger <juerg.haefliger@....com>,
linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] ata-sff: always map page before data transfer
> I don't understand all the factors at play here, so thoughts are definitely
> welcome.
I don't fully understand the old code either. One thing that is weird
is the "use a bounce buffer comment" which doesn't make any sense.
The other is the local_irq_save, which isn't really needed for
kmap_atomic to start with, but maybe that's the reason why the original
author didn't want to do it unconditionally?
So based on that:
> + /* FIXME: use a bounce buffer */
drop this comment..
> + local_irq_save(flags);
.. remove the local_irq_save/local_irq_restore ..
> + /* do the actual data transfer */
> + ap->ops->sff_data_xfer(qc, buf + offset, qc->sect_size,
> + do_write);
.. and a nice alittle cleanup move the do_write onto the previous line.
> + /* FIXME: use bounce buffer */
> + local_irq_save(flags);
> + buf = kmap_atomic(page);
>
> + /* do the actual data transfer */
> + consumed = ap->ops->sff_data_xfer(qc, buf + offset,
> + count, rw);
And same here.
And we should be fine.
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