Commit 0c6de0c9 authored by Menglong Dong's avatar Menglong Dong Committed by David S. Miller
Browse files

net: tipc: fix FB_MTU eat two pages 



FB_MTU is used in 'tipc_msg_build()' to alloc smaller skb when memory
allocation fails, which can avoid unnecessary sending failures.

The value of FB_MTU now is 3744, and the data size will be:

  (3744 + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) + \
    SKB_DATA_ALIGN(BUF_HEADROOM + BUF_TAILROOM + 3))

which is larger than one page(4096), and two pages will be allocated.

To avoid it, replace '3744' with a calculation:

  (PAGE_SIZE - SKB_DATA_ALIGN(BUF_OVERHEAD) - \
    SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))

What's more, alloc_skb_fclone() will call SKB_DATA_ALIGN for data size,
and it's not necessary to make alignment for buf_size in
tipc_buf_acquire(). So, just remove it.

Fixes: 4c94cc2d ("tipc: fall back to smaller MTU if allocation of local send skb fails")
Signed-off-by: default avatarMenglong Dong <dong.menglong@zte.com.cn>
Acked-by: default avatarJon Maloy <jmaloy@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1b077ce1

net/tipc/bcast.c

+1 −1
Original line number Diff line number Diff line
@@ -699,7 +699,7 @@ int tipc_bcast_init(struct net *net) 
	spin_lock_init(&tipc_net(net)->bclock);



	if (!tipc_link_bc_create(net, 0, 0, NULL,

				 FB_MTU,

				 one_page_mtu,

				 BCLINK_WIN_DEFAULT,

				 BCLINK_WIN_DEFAULT,

				 0,

net/tipc/msg.c

+8 −9
Original line number Diff line number Diff line
@@ -44,12 +44,15 @@ 
#define MAX_FORWARD_SIZE 1024

#ifdef CONFIG_TIPC_CRYPTO

#define BUF_HEADROOM ALIGN(((LL_MAX_HEADER + 48) + EHDR_MAX_SIZE), 16)

#define BUF_TAILROOM (TIPC_AES_GCM_TAG_SIZE)

#define BUF_OVERHEAD (BUF_HEADROOM + TIPC_AES_GCM_TAG_SIZE)

#else

#define BUF_HEADROOM (LL_MAX_HEADER + 48)

#define BUF_TAILROOM 16

#define BUF_OVERHEAD BUF_HEADROOM

#endif



const int one_page_mtu = PAGE_SIZE - SKB_DATA_ALIGN(BUF_OVERHEAD) -

			 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));



static unsigned int align(unsigned int i)

{

	return (i + 3) & ~3u;
@@ -69,13 +72,8 @@ static unsigned int align(unsigned int i) 
struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)

{

	struct sk_buff *skb;

#ifdef CONFIG_TIPC_CRYPTO

	unsigned int buf_size = (BUF_HEADROOM + size + BUF_TAILROOM + 3) & ~3u;

#else

	unsigned int buf_size = (BUF_HEADROOM + size + 3) & ~3u;

#endif



	skb = alloc_skb_fclone(buf_size, gfp);

	skb = alloc_skb_fclone(BUF_OVERHEAD + size, gfp);

	if (skb) {

		skb_reserve(skb, BUF_HEADROOM);

		skb_put(skb, size);
@@ -395,7 +393,8 @@ int tipc_msg_build(struct tipc_msg *mhdr, struct msghdr *m, int offset, 
		if (unlikely(!skb)) {

			if (pktmax != MAX_MSG_SIZE)

				return -ENOMEM;

			rc = tipc_msg_build(mhdr, m, offset, dsz, FB_MTU, list);

			rc = tipc_msg_build(mhdr, m, offset, dsz,

					    one_page_mtu, list);

			if (rc != dsz)

				return rc;

			if (tipc_msg_assemble(list))

net/tipc/msg.h

+2 −1
Original line number Diff line number Diff line
@@ -99,9 +99,10 @@ struct plist; 
#define MAX_H_SIZE                60	/* Largest possible TIPC header size */



#define MAX_MSG_SIZE (MAX_H_SIZE + TIPC_MAX_USER_MSG_SIZE)

#define FB_MTU                  3744

#define TIPC_MEDIA_INFO_OFFSET	5



extern const int one_page_mtu;



struct tipc_skb_cb {

	union {

		struct {