[Xen-devel] [PATCH] Fix blkback/blktap sysfs read bug.

["Joe Jin" <joe.jin@xxxxxxxxxx>]

Hi,

At backend driver blkback and blktap, when checking statistics information,
at the time vbd device remove, kernel will crash.

Below patch will fix it, please review and apply.

Signed-off-by: Joe Jin <joe.jin@xxxxxxxxxx>

 blkback/xenbus.c |    5 ++++-
 blktap/xenbus.c  |    5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)
---

diff -r 6061d5615522 drivers/xen/blkback/xenbus.c
--- a/drivers/xen/blkback/xenbus.c      Fri Jan 08 13:07:17 2010 +0000
+++ b/drivers/xen/blkback/xenbus.c      Tue Jan 19 17:37:32 2010 +0800
@@ -104,10 +104,13 @@
                                   struct device_attribute *attr,       \
                                   char *buf)                           \
        {                                                               \
+               ssize_t ret = -ENODEV;                                  \
                struct xenbus_device *dev = to_xenbus_device(_dev);     \
                struct backend_info *be = dev->dev.driver_data;         \
                                                                        \
-               return sprintf(buf, format, ##args);                    \
+               if (be && be->blkif)                                    \
+                       ret = sprintf(buf, format, ##args);             \
+               return ret;                                             \
        }                                                               \
        static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 
diff -r 6061d5615522 drivers/xen/blktap/xenbus.c
--- a/drivers/xen/blktap/xenbus.c       Fri Jan 08 13:07:17 2010 +0000
+++ b/drivers/xen/blktap/xenbus.c       Tue Jan 19 17:37:32 2010 +0800
@@ -122,10 +122,13 @@
                                   struct device_attribute *attr,       \
                                   char *buf)                           \
        {                                                               \
+               ssize_t ret = -ENODEV;                                  \
                struct xenbus_device *dev = to_xenbus_device(_dev);     \
                struct backend_info *be = dev->dev.driver_data;         \
                                                                        \
-               return sprintf(buf, format, ##args);                    \
+               if (be && be->blkif)                                    \
+                       ret = sprintf(buf, format, ##args);             \
+               return ret;                                             \
        }                                                               \
        static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 

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