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: 4c94cc2d3d57 ("tipc: fall back to smaller MTU if allocation of local send skb fails")
Signed-off-by: Menglong Dong <dong.menglong@zte.com.cn>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
index d4beca895992db6ea45b9e1776f3f2b916be0313..593846d252143c09eccd05a5e1192f92ca9dd36a 100644 (file)
--- a/net/tipc/bcast.c
+++ b/net/tipc/bcast.c
@@ -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,

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index ce6ab54822d8db184ac6b41dc380467668408547..7053c22e393e71f424459d31109a1d347e1b3736 100644 (file)
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -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))

diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 5d64596ba98775d5dfe2d2d4918bcc11273d485b..64ae4c4c44f8cdaabca9ca9430dc8be1b5048564 100644 (file)
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -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 {