While I would have wanted it to use DEFINE_RWLOCK(), it's probably
okay without. Or maybe you could adjust this as you check it in, Keir?
Acked-by: Jan Beulich <jbeulich@xxxxxxxxxx>
>>> "Joe Jin" <joe.jin@xxxxxxxxxx> 21.01.10 01:46 >>>
Hi,
Read blk{back,tap} statistics info after remove vbd device(s) kernel will crash.
Below patch will fix the race, please review and apply.
Signed-off-by: Joe Jin <joe.jin@xxxxxxxxxx>
Cc: Keir Fraser <keir.fraser@xxxxxxxxxx>
Cc: Jan Beulich <JBeulich@xxxxxxxxxx>
---
blkback/xenbus.c | 19 ++++++++++++++++---
blktap/xenbus.c | 18 +++++++++++++++---
2 files changed, 31 insertions(+), 6 deletions(-)
diff -r 0bec29c94ce9 drivers/xen/blkback/xenbus.c
--- a/drivers/xen/blkback/xenbus.c Mon Jan 18 14:50:43 2010 +0000
+++ b/drivers/xen/blkback/xenbus.c Thu Jan 21 08:38:58 2010 +0800
@@ -26,6 +26,8 @@
#define DPRINTK(fmt, args...) \
pr_debug("blkback/xenbus (%s:%d) " fmt ".\n", \
__FUNCTION__, __LINE__, ##args)
+
+static rwlock_t sysfs_read_lock = RW_LOCK_UNLOCKED;
struct backend_info
{
@@ -104,10 +106,19 @@
struct device_attribute *attr, \
char *buf) \
{ \
- struct xenbus_device *dev = to_xenbus_device(_dev); \
- struct backend_info *be = dev->dev.driver_data; \
+ ssize_t ret = -ENODEV; \
+ struct xenbus_device *dev; \
+ struct backend_info *be; \
\
- return sprintf(buf, format, ##args); \
+ if (!get_device(_dev)) \
+ return ret; \
+ dev = to_xenbus_device(_dev); \
+ read_lock(&sysfs_read_lock); \
+ if ((be = dev->dev.driver_data) != NULL) \
+ ret = sprintf(buf, format, ##args); \
+ read_unlock(&sysfs_read_lock); \
+ put_device(_dev); \
+ return ret; \
} \
static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
@@ -173,6 +184,7 @@
DPRINTK("");
+ write_lock(&sysfs_read_lock);
if (be->major || be->minor)
xenvbd_sysfs_delif(dev);
@@ -191,6 +203,7 @@
kfree(be);
dev->dev.driver_data = NULL;
+ write_unlock(&sysfs_read_lock);
return 0;
}
diff -r 0bec29c94ce9 drivers/xen/blktap/xenbus.c
--- a/drivers/xen/blktap/xenbus.c Mon Jan 18 14:50:43 2010 +0000
+++ b/drivers/xen/blktap/xenbus.c Thu Jan 21 08:38:58 2010 +0800
@@ -50,6 +50,7 @@
int group_added;
};
+static rwlock_t sysfs_read_lock = RW_LOCK_UNLOCKED;
static void connect(struct backend_info *);
static int connect_ring(struct backend_info *);
@@ -122,10 +123,19 @@
struct device_attribute *attr, \
char *buf) \
{ \
- struct xenbus_device *dev = to_xenbus_device(_dev); \
- struct backend_info *be = dev->dev.driver_data; \
+ ssize_t ret = -ENODEV; \
+ struct xenbus_device *dev; \
+ struct backend_info *be; \
\
- return sprintf(buf, format, ##args); \
+ if (!get_device(_dev)) \
+ return ret; \
+ dev = to_xenbus_device(_dev); \
+ read_lock(&sysfs_read_lock); \
+ if ((be = dev->dev.driver_data) != NULL) \
+ ret = sprintf(buf, format, ##args); \
+ read_unlock(&sysfs_read_lock); \
+ put_device(_dev); \
+ return ret; \
} \
static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
@@ -170,6 +180,7 @@
{
struct backend_info *be = dev->dev.driver_data;
+ write_lock(&sysfs_read_lock);
if (be->group_added)
xentap_sysfs_delif(be->dev);
if (be->backend_watch.node) {
@@ -187,6 +198,7 @@
}
kfree(be);
dev->dev.driver_data = NULL;
+ write_unlock(&sysfs_read_lock);
return 0;
}
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