aio: double aio_max_nr in calculations

With the changes to use percpu counters for aio event ring size calculation,
existing increases to aio_max_nr are now insufficient to allow for the
allocation of enough events.  Double the value used for aio_max_nr to account
for the doubling introduced by the percpu slack.
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>

fs/aio.c

@@ -490,7 +490,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 		return ERR_PTR(-EINVAL);
 	}
 
-	if (!nr_events || (unsigned long)nr_events > aio_max_nr)
+	if (!nr_events || (unsigned long)nr_events > (aio_max_nr * 2UL))
 		return ERR_PTR(-EAGAIN);
 
 	ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
@@ -522,7 +522,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 
 	/* limit the number of system wide aios */
 	spin_lock(&aio_nr_lock);
-	if (aio_nr + nr_events > aio_max_nr ||
+	if (aio_nr + nr_events > (aio_max_nr * 2UL) ||
 	    aio_nr + nr_events < aio_nr) {
 		spin_unlock(&aio_nr_lock);
 		goto out_cleanup;