From 6231e47b6fadf42da2e7a45b8272e80aed53c444 Mon Sep 17 00:00:00 2001 From: Tahsin Erdogan Date: Wed, 9 Aug 2023 09:47:52 -0700 Subject: [PATCH] tun: avoid high-order page allocation for packet header When gso.hdr_len is zero and a packet is transmitted via write() or writev(), all payload is treated as header which requires a contiguous memory allocation. This allocation request is harder to satisfy, and may even fail if there is enough fragmentation. Note that sendmsg() code path limits the linear copy length, so this change makes write()/writev() and sendmsg() paths more consistent. Signed-off-by: Tahsin Erdogan Acked-by: Jason Wang Reviewed-by: Eric Dumazet Reviewed-by: Willem de Bruijn Link: https://lore.kernel.org/r/20230809164753.2247594-1-trdgn@amazon.com Signed-off-by: Jakub Kicinski --- drivers/net/tun.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index a057654..d4bd762 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1523,7 +1523,7 @@ static struct sk_buff *tun_alloc_skb(struct tun_file *tfile, int err; /* Under a page? Don't bother with paged skb. */ - if (prepad + len < PAGE_SIZE || !linear) + if (prepad + len < PAGE_SIZE) linear = len; if (len - linear > MAX_SKB_FRAGS * (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) @@ -1840,6 +1840,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, */ zerocopy = false; } else { + if (!linear) + linear = min_t(size_t, good_linear, copylen); + skb = tun_alloc_skb(tfile, align, copylen, linear, noblock); } -- 2.7.4