diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 55869b362fdfb7c500177890443a6617e2107081..25c41ce070a7feb607eadabb84e52d5bda506fd2 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -179,6 +179,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) blkif->domid = domid; atomic_set(&blkif->refcnt, 1); init_completion(&blkif->drain_complete); + + /* + * Because freeing back to the cache may be deferred, it is not + * safe to unload the module (and hence destroy the cache) until + * this has completed. To prevent premature unloading, take an + * extra module reference here and release only when the object + * has been freed back to the cache. + */ + __module_get(THIS_MODULE); INIT_WORK(&blkif->free_work, xen_blkif_deferred_free); return blkif; @@ -328,6 +337,7 @@ static void xen_blkif_free(struct xen_blkif *blkif) /* Make sure everything is drained before shutting down */ kmem_cache_free(xen_blkif_cachep, blkif); + module_put(THIS_MODULE); } int __init xen_blkif_interface_init(void)