netdev - [PATCH bpf] devmap: Use GFP_KERNEL for xdp bulk queue allocation

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Date:   Tue, 9 Feb 2021 08:24:52 +0000
From:   NOMURA JUNICHI(野村　淳一) 
        <junichi.nomura@....com>
To:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "toke@...hat.com" <toke@...hat.com>,
        NOMURA JUNICHI(野村　淳一) 
        <junichi.nomura@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH bpf] devmap: Use GFP_KERNEL for xdp bulk queue allocation

The devmap bulk queue is allocated with GFP_ATOMIC and the allocation may
fail if there is no available space in existing percpu pool.

Since commit 75ccae62cb8d42 ("xdp: Move devmap bulk queue into struct net_device")
moved the bulk queue allocation to NETDEV_REGISTER callback, whose context
is allowed to sleep, use GFP_KERNEL instead of GFP_ATOMIC to let percpu
allocator extend the pool when needed and avoid possible failure of netdev
registration.

As the required alignment is natural, we can simply use alloc_percpu().

Signed-off-by: Jun'ichi Nomura <junichi.nomura@....com>

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index f6e9c68afdd4..f4d3fe8e0652 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -803,8 +803,7 @@ static int dev_map_notification(struct notifier_block *notifier,

 		/* will be freed in free_netdev() */
 		netdev->xdp_bulkq =
-			__alloc_percpu_gfp(sizeof(struct xdp_dev_bulk_queue),
-					   sizeof(void *), GFP_ATOMIC);
+			alloc_percpu(struct xdp_dev_bulk_queue);
 		if (!netdev->xdp_bulkq)
 			return NOTIFY_BAD;