USB: Fix off-by-1 error in the scatter-gather library

The loop in usb_sg_wait() is structured in a way that makes it hard to
tell, when the loop exits, whether or not the last URB submission
succeeded.  This patch (as928) changes it from a "for" loop to a
"while" loop and keeps "i" always equal to the number of successful
submissions.  This fixes an off-by-one error which can show up when
the first URB submission fails.

The patch also removes a couple of lines that initialize fields which
don't need to be initialized.

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

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index f9fed34..4c14323 100644 (file)
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -404,8 +404,6 @@ int usb_sg_init (
 
                io->urbs [i]->complete = sg_complete;
                io->urbs [i]->context = io;
-               io->urbs [i]->status = -EINPROGRESS;
-               io->urbs [i]->actual_length = 0;
 
                /*
                 * Some systems need to revert to PIO when DMA is temporarily
@@ -499,7 +497,8 @@ void usb_sg_wait (struct usb_sg_request *io)
 
        /* queue the urbs.  */
        spin_lock_irq (&io->lock);
-       for (i = 0; i < entries && !io->status; i++) {
+       i = 0;
+       while (i < entries && !io->status) {
                int     retval;
 
                io->urbs [i]->dev = io->dev;
@@ -516,7 +515,6 @@ void usb_sg_wait (struct usb_sg_request *io)
                case -ENOMEM:
                        io->urbs[i]->dev = NULL;
                        retval = 0;
-                       i--;
                        yield ();
                        break;
 
@@ -527,6 +525,7 @@ void usb_sg_wait (struct usb_sg_request *io)
                         * URBs are queued at once; N milliseconds?
                         */
                case 0:
+                       ++i;
                        cpu_relax ();
                        break;