net-sysfs: remove possible sleep from an RCU read-side critical section

xps_queue_show is mostly made of an RCU read-side critical section and
calls bitmap_zalloc with GFP_KERNEL in the middle of it. That is not
allowed as this call may sleep and such behaviours aren't allowed in RCU
read-side critical sections. Fix this by using GFP_NOWAIT instead.

Fixes: 5478fcd0f483 ("net: embed nr_ids in the xps maps")
Reported-by: kernel test robot <oliver.sang@intel.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 562a42f..f619777 100644 (file)
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1378,7 +1378,7 @@ static ssize_t xps_queue_show(struct net_device *dev, unsigned int index,
        nr_ids = dev_maps ? dev_maps->nr_ids :
                 (type == XPS_CPUS ? nr_cpu_ids : dev->num_rx_queues);
 
-       mask = bitmap_zalloc(nr_ids, GFP_KERNEL);
+       mask = bitmap_zalloc(nr_ids, GFP_NOWAIT);
        if (!mask) {
                rcu_read_unlock();
                return -ENOMEM;