[Xen-changelog] [linux-2.6.18-xen] blktap: bugfix and support extended device numbers

["Xen patchbot-linux-2.6.18-xen" <patchbot-linux-2.6.18-xen@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1214579276 -3600
# Node ID b29a06ba7a5ff8c85054d56a4135ac38925422c0
# Parent  65faf5fc61a1cadb20885dc2e926efe1722956fd
blktap: bugfix and support extended device numbers

This simple patch puts two fixes into the blktap backend.  The first
is a change of busid from an unsigned short to a u32 so we can
accommodate the new expanded format (which doesn't fit into 16-bits).
The second is a minor fix to signal_tapdisk(); while developing, if
the tools happen to set up the tapfds wrong, you can get into a
situation where the idx passed to signal_tapdisk() is NULL, causing a
kernel OOPS.  The fix for signal_tapdisk() just returns if the idx is
negative, preventing the crash.

Signed-off-by: Chris Lalancette <clalance@xxxxxxxxxx>
---
 drivers/xen/blktap/blktap.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletion(-)

diff -r 65faf5fc61a1 -r b29a06ba7a5f drivers/xen/blktap/blktap.c
--- a/drivers/xen/blktap/blktap.c       Fri Jun 27 16:06:41 2008 +0100
+++ b/drivers/xen/blktap/blktap.c       Fri Jun 27 16:07:56 2008 +0100
@@ -89,7 +89,7 @@ static int mmap_pages = MMAP_PAGES;
 /*Data struct handed back to userspace for tapdisk device to VBD mapping*/
 typedef struct domid_translate {
        unsigned short domid;
-       unsigned short busid;
+       u32 busid;
 } domid_translate_t ;
 
 /*Data struct associated with each of the tapdisk devices*/
@@ -508,6 +508,13 @@ void signal_tapdisk(int idx)
        tap_blkif_t *info;
        struct task_struct *ptask;
 
+       /*
+        * if the userland tools set things up wrong, this could be negative;
+        * just don't try to signal in this case
+        */
+       if (idx < 0)
+               return;
+
        info = tapfds[idx];
        if ((idx < 0) || (idx > MAX_TAP_DEV) || !info)
                return;

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