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From: Alan Stern <stern@rowland.harvard.edu>
To: Oliver Neukum <oneukum@suse.com>
Cc: Jaewon Kim <jaewon31.kim@gmail.com>,
	Christoph Hellwig <hch@infradead.org>, <linux-mm@kvack.org>,
	<gregkh@linuxfoundation.org>,
	Jaewon Kim <jaewon31.kim@samsung.com>, <m.szyprowski@samsung.com>,
	<ytk.lee@samsung.com>, <linux-kernel@vger.kernel.org>,
	<linux-usb@vger.kernel.org>
Subject: Re: [RFC PATCH] usb: host: xhci: allow __GFP_FS in dma allocation
Date: Wed, 22 May 2019 10:56:01 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1905221055190.1410-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <1558506702.12672.28.camel@suse.com>

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


  reply	other threads:[~2019-05-22 14:56 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-17 16:02 Jaewon Kim
2019-05-17 16:34 ` Matthew Wilcox
2019-05-18  1:53   ` Jaewon Kim
2019-05-20  5:56 ` Christoph Hellwig
2019-05-20  9:09   ` Oliver Neukum
2019-05-20 10:12     ` Christoph Hellwig
2019-05-20 14:16       ` Alan Stern
2019-05-20 14:23         ` Christoph Hellwig
2019-05-21  8:54           ` Oliver Neukum
2019-05-21 13:27             ` Christoph Hellwig
2019-05-21 13:11         ` Oliver Neukum
2019-05-21 14:00           ` Alan Stern
2019-05-22  6:31             ` Oliver Neukum
2019-05-22 14:56               ` Alan Stern [this message]
2019-05-22 20:47                 ` Oliver Neukum
2019-05-23 14:01                   ` Alan Stern
2019-05-28 12:34                     ` Oliver Neukum
2019-05-28 14:25                       ` Alan Stern
2019-05-23 12:32   ` Oliver Neukum
2019-05-23 16:35     ` Christoph Hellwig

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