linux-kernel - Re: [PATCH] usb/core/devio.c: Don't use GFP_KERNEL while we cannot reset a storage device

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Message-ID: <Pine.LNX.4.44L0.1303081248090.17427-100000@netrider.rowland.org>
Date:	Fri, 8 Mar 2013 12:55:08 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	Oliver Neukum <oliver@...kum.org>
cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Hans de Goede <hdegoede@...hat.com>,
	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	<ldv-project@...uxtesting.org>
Subject: Re: [PATCH] usb/core/devio.c: Don't use GFP_KERNEL while we cannot
 reset a storage device

On Sat, 9 Mar 2013, Alexey Khoroshilov wrote:

> As it was described by Oliver Neukum in commit acbe2fe
> "USB: Don't use GFP_KERNEL while we cannot reset a storage device":
> 
>   Memory allocations with GFP_KERNEL can cause IO to a storage device
>   which can fail resulting in a need to reset the device. Therefore
>   GFP_KERNEL cannot be safely used between usb_lock_device()
>   and usb_unlock_device(). Replace by GFP_NOIO.
> 
> The patch fixes the same issue in usb/core/devio.c.
> All the allocations fixed are under usb_lock_device() from usbdev_do_ioctl().
> 
> Found by Linux Driver Verification project (linuxtesting.org).

I don't know if this is a good idea.  People can and do submit 
transfers requiring a lot of buffer space.  Switching to GFP_NOIO 
will make those allocations a lot more likely to fail.

Oliver, what do you think?

Alan Stern

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