net: af_packet: remove last_kactive_blk_num field

kactive_blk_num (K) is only incremented on block close.
In timer callback prb_retire_rx_blk_timer_expired, except delete_blk_timer
is true, last_kactive_blk_num (L) is set to match kactive_blk_num (K) in
all cases. L is also set to match K in prb_open_block.
The only case K not equal to L is when scheduled by tpacket_rcv
and K is just incremented on block close but no new block could be opened,
so that it does not call prb_open_block in prb_dispatch_next_block.
This patch modifies the prb_retire_rx_blk_timer_expired function by simply
removing the check for L == K. This patch just provides another checkpoint
to thaw the might-be-frozen block in any case. It doesn't have any effect
because __packet_lookup_frame_in_block() has the same logic and does it
again without this patch when detecting the ring is frozen. The patch only
advances checking the status of the ring.

Suggested-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Reviewed-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://lore.kernel.org/all/20250831100822.1238795-1-jackzxcui1989@163.com/
Signed-off-by: Xin Zhao <jackzxcui1989@163.com>
Link: https://patch.msgid.link/20250908104549.204412-2-jackzxcui1989@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 9d42c4bd6e390c7212fc0a8dde5cc14ba7a00d53..230cb87646152b5daf3cb49ecfa2e1feee94aa5b 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -669,7 +669,6 @@ static void init_prb_bdqc(struct packet_sock *po,
        p1->knum_blocks = req_u->req3.tp_block_nr;
        p1->hdrlen = po->tp_hdrlen;
        p1->version = po->tp_version;
-       p1->last_kactive_blk_num = 0;
        po->stats.stats3.tp_freeze_q_cnt = 0;
        if (req_u->req3.tp_retire_blk_tov)
                p1->retire_blk_tov = req_u->req3.tp_retire_blk_tov;
@@ -693,7 +692,6 @@ static void _prb_refresh_rx_retire_blk_timer(struct tpacket_kbdq_core *pkc)
 {
        mod_timer(&pkc->retire_blk_timer,
                        jiffies + pkc->tov_in_jiffies);
-       pkc->last_kactive_blk_num = pkc->kactive_blk_num;
 }
 
 /*
@@ -750,38 +748,36 @@ static void prb_retire_rx_blk_timer_expired(struct timer_list *t)
                write_unlock(&pkc->blk_fill_in_prog_lock);
        }
 
-       if (pkc->last_kactive_blk_num == pkc->kactive_blk_num) {
-               if (!frozen) {
-                       if (!BLOCK_NUM_PKTS(pbd)) {
-                               /* An empty block. Just refresh the timer. */
-                               goto refresh_timer;
-                       }
-                       prb_retire_current_block(pkc, po, TP_STATUS_BLK_TMO);
-                       if (!prb_dispatch_next_block(pkc, po))
-                               goto refresh_timer;
-                       else
-                               goto out;
+       if (!frozen) {
+               if (!BLOCK_NUM_PKTS(pbd)) {
+                       /* An empty block. Just refresh the timer. */
+                       goto refresh_timer;
+               }
+               prb_retire_current_block(pkc, po, TP_STATUS_BLK_TMO);
+               if (!prb_dispatch_next_block(pkc, po))
+                       goto refresh_timer;
+               else
+                       goto out;
+       } else {
+               /* Case 1. Queue was frozen because user-space was
+                * lagging behind.
+                */
+               if (prb_curr_blk_in_use(pbd)) {
+                       /*
+                        * Ok, user-space is still behind.
+                        * So just refresh the timer.
+                        */
+                       goto refresh_timer;
                } else {
-                       /* Case 1. Queue was frozen because user-space was
-                        *         lagging behind.
+                       /* Case 2. queue was frozen,user-space caught up,
+                        * now the link went idle && the timer fired.
+                        * We don't have a block to close.So we open this
+                        * block and restart the timer.
+                        * opening a block thaws the queue,restarts timer
+                        * Thawing/timer-refresh is a side effect.
                         */
-                       if (prb_curr_blk_in_use(pbd)) {
-                               /*
-                                * Ok, user-space is still behind.
-                                * So just refresh the timer.
-                                */
-                               goto refresh_timer;
-                       } else {
-                              /* Case 2. queue was frozen,user-space caught up,
-                               * now the link went idle && the timer fired.
-                               * We don't have a block to close.So we open this
-                               * block and restart the timer.
-                               * opening a block thaws the queue,restarts timer
-                               * Thawing/timer-refresh is a side effect.
-                               */
-                               prb_open_block(pkc, pbd);
-                               goto out;
-                       }
+                       prb_open_block(pkc, pbd);
+                       goto out;
                }
        }
 

diff --git a/net/packet/internal.h b/net/packet/internal.h
index 1e743d0316fdda573d8987df6a344dfaf6a524b5..d367b9f93a73a09e346086071df7978c1fd73d2c 100644 (file)
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -24,12 +24,6 @@ struct tpacket_kbdq_core {
        unsigned short  kactive_blk_num;
        unsigned short  blk_sizeof_priv;
 
-       /* last_kactive_blk_num:
-        * trick to see if user-space has caught up
-        * in order to avoid refreshing timer when every single pkt arrives.
-        */
-       unsigned short  last_kactive_blk_num;
-
        char            *pkblk_start;
        char            *pkblk_end;
        int             kblk_size;