Commit fa2ac657 authored by Paul Durrant's avatar Paul Durrant Committed by Juergen Gross
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xen-blkback: prevent premature module unload

Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
cache. This cache is destoyed when xen-blkif is unloaded so it is
necessary to wait for the deferred free routine used for such objects to
complete. This necessity was missed in commit 14855954

allow module to be cleanly unloaded". This patch fixes the problem by
taking/releasing extra module references in xen_blkif_alloc/free()
Signed-off-by: default avatarPaul Durrant <>
Reviewed-by: default avatarRoger Pau Monné <>
Signed-off-by: default avatarJuergen Gross <>
parent 14855954
......@@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
blkif->domid = domid;
atomic_set(&blkif->refcnt, 1);
* 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.
INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
return blkif;
......@@ -320,6 +329,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
/* Make sure everything is drained before shutting down */
kmem_cache_free(xen_blkif_cachep, blkif);
int __init xen_blkif_interface_init(void)
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