From: Tahsin Erdogan Date: Wed, 9 Aug 2023 16:47:52 +0000 (-0700) Subject: tun: avoid high-order page allocation for packet header X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=6231e47b6fadf42da2e7a45b8272e80aed53c444;p=linux.git 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 --- diff --git a/drivers/net/tun.c b/drivers/net/tun.c index a057654488031..d4bd76297a2aa 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); }