xen-blkback: prevent premature module unload (fa2ac657) · Commits · 戴 / test

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 "xen-blkback: allow module to be cleanly unloaded". This patch fixes the problem by taking/releasing extra module references in xen_blkif_alloc/free() respectively. Signed-off-by:

Paul Durrant <pdurrant@amazon.com> Reviewed-by:

Roger Pau Monné <roger.pau@citrix.com> Signed-off-by:

Juergen Gross <jgross@suse.com>

drivers/block/xen-blkback/xenbus.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -171,6 +171,15 @@ 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;
		@@ -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);
		module_put(THIS_MODULE);
		}

		int __init xen_blkif_interface_init(void)

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