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Subject[PATCH] xen/blkback: prevent repeated backend_changed invocations
Date
backend_changed might be called multiple times, which will leak
be->mode. Make sure it will be called only once. Remove some unneeded
checks. Also the be->mode string was leaked, release the memory on
device shutdown.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---

incorporate all comments from Jan.
fold the oneline change to xen_blkbk_remove into this change
now its compile tested.

drivers/block/xen-blkback/xenbus.c | 69 ++++++++++++++++++--------------------
1 file changed, 33 insertions(+), 36 deletions(-)

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index f58434c..5ca77c3 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -28,6 +28,7 @@ struct backend_info {
unsigned major;
unsigned minor;
char *mode;
+ unsigned alive;
};

static struct kmem_cache *xen_blkif_cachep;
@@ -366,6 +367,7 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
be->blkif = NULL;
}

+ kfree(be->mode);
kfree(be);
dev_set_drvdata(&dev->dev, NULL);
return 0;
@@ -501,10 +503,14 @@ static void backend_changed(struct xenbus_watch *watch,
= container_of(watch, struct backend_info, backend_watch);
struct xenbus_device *dev = be->dev;
int cdrom = 0;
- char *device_type;
+ char *device_type, *p;
+ long handle;

DPRINTK("");

+ if (be->alive)
+ return;
+
err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
&major, &minor);
if (XENBUS_EXIST_ERR(err)) {
@@ -520,12 +526,7 @@ static void backend_changed(struct xenbus_watch *watch,
return;
}

- if ((be->major || be->minor) &&
- ((be->major != major) || (be->minor != minor))) {
- pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
- be->major, be->minor, major, minor);
- return;
- }
+ be->alive = 1;

be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
if (IS_ERR(be->mode)) {
@@ -541,39 +542,35 @@ static void backend_changed(struct xenbus_watch *watch,
kfree(device_type);
}

- if (be->major == 0 && be->minor == 0) {
- /* Front end dir is a number, which is used as the handle. */
-
- char *p = strrchr(dev->otherend, '/') + 1;
- long handle;
- err = strict_strtoul(p, 0, &handle);
- if (err)
- return;
-
- be->major = major;
- be->minor = minor;
+ /* Front end dir is a number, which is used as the handle. */
+ p = strrchr(dev->otherend, '/') + 1;
+ err = strict_strtoul(p, 0, &handle);
+ if (err)
+ return;

- err = xen_vbd_create(be->blkif, handle, major, minor,
- (NULL == strchr(be->mode, 'w')), cdrom);
- if (err) {
- be->major = 0;
- be->minor = 0;
- xenbus_dev_fatal(dev, err, "creating vbd structure");
- return;
- }
+ be->major = major;
+ be->minor = minor;

- err = xenvbd_sysfs_addif(dev);
- if (err) {
- xen_vbd_free(&be->blkif->vbd);
- be->major = 0;
- be->minor = 0;
- xenbus_dev_fatal(dev, err, "creating sysfs entries");
- return;
- }
+ err = xen_vbd_create(be->blkif, handle, major, minor,
+ (NULL == strchr(be->mode, 'w')), cdrom);
+ if (err) {
+ be->major = 0;
+ be->minor = 0;
+ xenbus_dev_fatal(dev, err, "creating vbd structure");
+ return;
+ }

- /* We're potentially connected now */
- xen_update_blkif_status(be->blkif);
+ err = xenvbd_sysfs_addif(dev);
+ if (err) {
+ xen_vbd_free(&be->blkif->vbd);
+ be->major = 0;
+ be->minor = 0;
+ xenbus_dev_fatal(dev, err, "creating sysfs entries");
+ return;
}
+
+ /* We're potentially connected now */
+ xen_update_blkif_status(be->blkif);
}


--
1.8.0.1


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