Re: [PATCH] tun: make tun_build_skb() thread safe
flat view
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2017-08-16 16:55:18
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On Wed, Aug 16, 2017 at 10:14:33PM +0800, Jason Wang wrote:
From: Eric Dumazet <redacted>
tun_build_skb() is not thread safe since it uses per queue page frag,
this will break things when multiple threads are sending through same
queue. Switch to use per-thread generator (no lock involved).
Fixes: 66ccbc9c87c2 ("tap: use build_skb() for small packet")
Tested-by: Jason Wang <redacted>
Signed-off-by: Eric Dumazet <redacted>
Signed-off-by: Jason Wang <redacted>Acked-by: Michael S. Tsirkin <mst@redhat.com> Jason, given the switch to task_frag, would it be worth it to look at using higher order allocs along the lines of 5640f7685831e088fe6c2e1f863a6805962f8e81 as well?
quoted hunk ↗ jump to hunk
--- drivers/net/tun.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 5892284..c38cd84 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c@@ -175,7 +175,6 @@ struct tun_file { struct list_head next; struct tun_struct *detached; struct skb_array tx_array; - struct page_frag alloc_frag; }; struct tun_flow_entry {@@ -578,8 +577,6 @@ static void __tun_detach(struct tun_file *tfile, bool clean) } if (tun) skb_array_cleanup(&tfile->tx_array); - if (tfile->alloc_frag.page) - put_page(tfile->alloc_frag.page); sock_put(&tfile->sk); } }@@ -1272,7 +1269,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun, struct virtio_net_hdr *hdr, int len, int *generic_xdp) { - struct page_frag *alloc_frag = &tfile->alloc_frag; + struct page_frag *alloc_frag = ¤t->task_frag; struct sk_buff *skb; struct bpf_prog *xdp_prog; int buflen = SKB_DATA_ALIGN(len + TUN_RX_PAD) +@@ -2580,8 +2577,6 @@ static int tun_chr_open(struct inode *inode, struct file * file) tfile->sk.sk_write_space = tun_sock_write_space; tfile->sk.sk_sndbuf = INT_MAX; - tfile->alloc_frag.page = NULL; - file->private_data = tfile; INIT_LIST_HEAD(&tfile->next);-- 2.7.4