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CacheFiles: Handle object being killed before being set up
If a cache object gets killed whilst in the process of being set up - for instance if the netfs relinquishes the cookie that the object is associated with - then the object's state machine will transit to the DROP_OBJECT state without necessarily going through the LOOKUP_OBJECT or CREATE_OBJECT states. This is a problem for CacheFiles because cachefiles_drop_object() assumes that object->dentry will be set upon reaching the DROP_OBJECT state and has an ASSERT() to that effect (see the oops below) - but object->dentry doesn't get set until the LOOKUP_OBJECT or CREATE_OBJECT states (and not always then if they fail). To fix this, just make the dentry cleanup in cachefiles_drop_object() conditional on the dentry actually being set and remove the assertion. CacheFiles: Assertion failed ------------[ cut here ]------------ kernel BUG at .../fs/cachefiles/namei.c:425! ... Workqueue: fscache_object fscache_object_work_func [fscache] ... RIP: ... cachefiles_delete_object+0xcd/0x110 [cachefiles] ... Call Trace: [<ffffffffa043280f>] ? cachefiles_drop_object+0xff/0x130 [cachefiles] [<ffffffffa02ac511>] ? fscache_drop_object+0xd1/0x1d0 [fscache] [<ffffffffa02ac697>] ? fscache_object_work_func+0x87/0x210 [fscache] [<ffffffff81080635>] ? process_one_work+0x155/0x450 [<ffffffff81081c44>] ? worker_thread+0x114/0x370 [<ffffffff81081b30>] ? manage_workers.isra.21+0x2c0/0x2c0 [<ffffffff81087fcc>] ? kthread+0xbc/0xe0 [<ffffffff81087f10>] ? flush_kthread_worker+0xa0/0xa0 [<ffffffff8150638c>] ? ret_from_fork+0x7c/0xb0 [<ffffffff81087f10>] ? flush_kthread_worker+0xa0/0xa0 Reported-by: Manuel Schölling <manuel.schoelling@gmx.de> Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com>
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@ -268,20 +268,27 @@ static void cachefiles_drop_object(struct fscache_object *_object)
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ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
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#endif
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/* delete retired objects */
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if (test_bit(FSCACHE_OBJECT_RETIRED, &object->fscache.flags) &&
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_object != cache->cache.fsdef
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) {
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_debug("- retire object OBJ%x", object->fscache.debug_id);
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cachefiles_begin_secure(cache, &saved_cred);
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cachefiles_delete_object(cache, object);
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cachefiles_end_secure(cache, saved_cred);
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}
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/* We need to tidy the object up if we did in fact manage to open it.
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* It's possible for us to get here before the object is fully
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* initialised if the parent goes away or the object gets retired
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* before we set it up.
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*/
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if (object->dentry) {
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/* delete retired objects */
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if (test_bit(FSCACHE_OBJECT_RETIRED, &object->fscache.flags) &&
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_object != cache->cache.fsdef
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) {
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_debug("- retire object OBJ%x", object->fscache.debug_id);
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cachefiles_begin_secure(cache, &saved_cred);
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cachefiles_delete_object(cache, object);
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cachefiles_end_secure(cache, saved_cred);
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}
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/* close the filesystem stuff attached to the object */
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if (object->backer != object->dentry)
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dput(object->backer);
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object->backer = NULL;
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/* close the filesystem stuff attached to the object */
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if (object->backer != object->dentry)
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dput(object->backer);
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object->backer = NULL;
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}
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/* note that the object is now inactive */
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if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
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