USB: add USB-Persist facility

This patch (as886) adds the controversial USB-persist facility,
allowing USB devices to persist across a power loss during system
suspend.

The facility is controlled by a new Kconfig option (with appropriate
warnings about the potential dangers); when the option is off the
behavior will remain the same as it is now.  But when the option is
on, people will be able to use suspend-to-disk and keep their USB
filesystems intact -- something particularly valuable for small
machines where the root filesystem is on a USB device!

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index df5dc186aef5..be4cd8fe4ce6 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -236,7 +236,7 @@ static void storage_pre_reset(struct usb_interface *iface)
         mutex_lock(&us->dev_mutex);
 }
 
-static void storage_post_reset(struct usb_interface *iface)
+static void storage_post_reset(struct usb_interface *iface, int reset_resume)
 {
         struct us_data *us = usb_get_intfdata(iface);
 
@@ -249,7 +249,11 @@ static void storage_post_reset(struct usb_interface *iface)
 
         /* FIXME: Notify the subdrivers that they need to reinitialize
          * the device */
-        mutex_unlock(&us->dev_mutex);
+
+        /* If this is a reset-resume then the pre_reset routine wasn't
+         * called, so we don't need to unlock the mutex. */
+        if (!reset_resume)
+                mutex_unlock(&us->dev_mutex);
 }
 
 /*