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tun: avoid high-order page allocation for packet header

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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 <trdgn@amazon.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20230809164753.2247594-1-trdgn@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Tahsin Erdogan 2023-08-09 09:47:52 -07:00 committed by Jakub Kicinski
parent 5604ac35cb
commit 6231e47b6f
1 changed files with 4 additions and 1 deletions
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5
drivers/net/tun.c
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@ -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);
}