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[195.135.220.15]) by mx.google.com with ESMTPS id c8si9742641eds.136.2019.05.21.23.31.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 May 2019 23:31:45 -0700 (PDT) Received-SPF: pass (google.com: domain of oneukum@suse.com designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of oneukum@suse.com designates 195.135.220.15 as permitted sender) smtp.mailfrom=oneukum@suse.com X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B08E1B01F; Wed, 22 May 2019 06:31:44 +0000 (UTC) Message-ID: <1558506702.12672.28.camel@suse.com> Subject: Re: [RFC PATCH] usb: host: xhci: allow __GFP_FS in dma allocation From: Oliver Neukum To: Alan Stern Cc: Jaewon Kim , Christoph Hellwig , linux-mm@kvack.org, gregkh@linuxfoundation.org, Jaewon Kim , m.szyprowski@samsung.com, ytk.lee@samsung.com, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Date: Wed, 22 May 2019 08:31:42 +0200 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Di, 2019-05-21 at 10:00 -0400, Alan Stern wrote: > > Changing configurations amounts to much the same as disconnecting, > because both operations destroy all the existing interfaces. > > Disconnect can arise in two different ways. > > Physical hot-unplug: All I/O operations will fail. > > Rmmod or unbind: I/O operations will succeed. > > The second case is probably okay. The first we can do nothing about. > However, in either case we do need to make sure that memory allocations > do not require any writebacks. This suggests that we need to call > memalloc_noio_save() from within usb_unbind_interface(). I agree with the problem, but I fail to see why this issue would be specific to USB. Shouldn't this be done in the device core layer? Regards Oliver