If one storage interface or usb network interface(iSCSI case)
exists in current configuration, memory allocation with
GFP_KERNEL during usb_device_reset() might trigger I/O transfer
on the storage interface itself and cause deadlock because
the 'us->dev_mutex' is held in .pre_reset() and the storage
interface can't do I/O transfer when the reset is triggered
by other interface, or the error handling can't be completed
if the reset is triggered by the storage itself(error handling path).
Cc: Alan Stern <st...@rowland.harvard.edu>
Cc: Oliver Neukum <oneu...@suse.de>
Signed-off-by: Ming Lei <ming....@canonical.com>
---
v5:
        - use inline memalloc_noio_save()
v4:
        - mark current memalloc_noio for every usb device reset
---
 drivers/usb/core/hub.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 90accde..2d5cc1c 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -5040,6 +5040,7 @@ int usb_reset_device(struct usb_device *udev)
 {
        int ret;
        int i;
+       unsigned int noio_flag;
        struct usb_host_config *config = udev->actconfig;
 
        if (udev->state == USB_STATE_NOTATTACHED ||
@@ -5049,6 +5050,17 @@ int usb_reset_device(struct usb_device *udev)
                return -EINVAL;
        }
 
+       /*
+        * Don't allocate memory with GFP_KERNEL in current
+        * context to avoid possible deadlock if usb mass
+        * storage interface or usbnet interface(iSCSI case)
+        * is included in current configuration. The easist
+        * approach is to do it for every device reset,
+        * because the device 'memalloc_noio' flag may have
+        * not been set before reseting the usb device.
+        */
+       noio_flag = memalloc_noio_save();
+
        /* Prevent autosuspend during the reset */
        usb_autoresume_device(udev);
 
@@ -5093,6 +5105,7 @@ int usb_reset_device(struct usb_device *udev)
        }
 
        usb_autosuspend_device(udev);
+       memalloc_noio_restore(noio_flag);
        return ret;
 }
 EXPORT_SYMBOL_GPL(usb_reset_device);
-- 
1.7.9.5

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