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: <CACVXFVNuJa0i9gtUWP2tVexwjKF0k1MJ2bA9V5M28LUWFJt5DQ@mail.gmail.com>
Date:	Mon, 11 Mar 2013 21:31:03 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Alexey Khoroshilov <khoroshilov@...ras.ru>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-usb@...r.kernel.org, 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, Mar 9, 2013 at 12:50 AM, Alexey Khoroshilov
<khoroshilov@...ras.ru> 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().

I am wondering why the device lock is needed for usbdev_do_ioctl()? Looks
device lock isn't required for USB transfer of kernel driver.


Thanks,
-- 
Ming Lei
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