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[192.131.102.54]) by mx.google.com with SMTP id k93si396757qte.13.2019.05.22.07.56.02 for ; Wed, 22 May 2019 07:56:02 -0700 (PDT) Received-SPF: pass (google.com: domain of stern+5cece118@rowland.harvard.edu designates 192.131.102.54 as permitted sender) client-ip=192.131.102.54; Authentication-Results: mx.google.com; spf=pass (google.com: domain of stern+5cece118@rowland.harvard.edu designates 192.131.102.54 as permitted sender) smtp.mailfrom=stern+5cece118@rowland.harvard.edu Received: (qmail 2691 invoked by uid 2102); 22 May 2019 10:56:01 -0400 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 22 May 2019 10:56:01 -0400 Date: Wed, 22 May 2019 10:56:01 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Oliver Neukum cc: Jaewon Kim , Christoph Hellwig , , , Jaewon Kim , , , , Subject: Re: [RFC PATCH] usb: host: xhci: allow __GFP_FS in dma allocation In-Reply-To: <1558506702.12672.28.camel@suse.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII 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 Wed, 22 May 2019, Oliver Neukum wrote: > 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? Only for drivers that are on the block-device writeback path. The device core doesn't know which drivers these are. Alan Stern