On 6/18/21 2:57 AM, menglong8.d...@gmail.com wrote:
From: Menglong Dong <dong.mengl...@zte.com.cn>
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.mengl...@zte.com.cn>
---
V4:
- fallback to V2
V3:
- split tipc_msg_build to tipc_msg_build and tipc_msg_frag
- introduce tipc_buf_acquire_flex, which is able to alloc skb for
local message
- add the variate 'local' in tipc_msg_build to check if this is a
local message.
V2:
- define FB_MTU in msg.c instead of introduce a new file
- remove align for buf_size in tipc_buf_acquire()
---
net/tipc/bcast.c | 2 +-
net/tipc/msg.c | 19 ++++++++++---------
net/tipc/msg.h | 3 ++-
3 files changed, 13 insertions(+), 11 deletions(-)
diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
index d4beca895992..593846d25214 100644
--- 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 ce6ab54822d8..912d17b3fc01 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -44,12 +44,17 @@
#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
+#define ONE_PAGE_SKB_SZ (PAGE_SIZE - SKB_DATA_ALIGN(BUF_OVERHEAD) - \
+ SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+
I suggest one small simplification:
Let's just skip this macro completely, and assign the calculation
directly to one_page_mtu below.
Otherwise:
Acked-by: Jon Maloy <jma...@redhat.com>
+const int one_page_mtu = ONE_PAGE_SKB_SZ;
+
static unsigned int align(unsigned int i)
{
return (i + 3) & ~3u;
@@ -69,13 +74,8 @@ 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 +395,8 @@ 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_SKB_SZ, list);
if (rc != dsz)
return rc;
if (tipc_msg_assemble(list))
diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 5d64596ba987..64ae4c4c44f8 100644
--- 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 {
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