linux-kernel - Re: [RFC PATCH] usb: host: xhci: allow __GFP

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Date:   Mon, 20 May 2019 03:12:06 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Jaewon Kim <jaewon31.kim@...il.com>, linux-mm@...ck.org,
        gregkh@...uxfoundation.org, Jaewon Kim <jaewon31.kim@...sung.com>,
        m.szyprowski@...sung.com, ytk.lee@...sung.com,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFC PATCH] usb: host: xhci: allow __GFP_FS in dma allocation

On Mon, May 20, 2019 at 11:09:25AM +0200, Oliver Neukum wrote:
> we actually do. It is just higher up in the calling path:

Perfect!

> So, do we need to audit the mem_flags again?
> What are we supposed to use? GFP_KERNEL?

GFP_KERNEL if you can block, GFP_ATOMIC if you can't for a good reason,
that is the allocation is from irq context or under a spinlock.  If you
think you have a case where you think you don't want to block, but it
is not because of the above reasons we need to have a chat about the
details.