mac80211: do not compute offset from ssn in Rx AMPDU reordering buffer

Currently, frames that go into the reordering buffer are stored at
index ieee80211_sn_sub(sn, tid_rx->ssn) % tid_rx->buf_size.

The offset calculation to the starting sequence number (SSN) is
useless and just adds overhead so simply use sn % tid_rx->buf_size.

This means the reordering buffer will start to be filled somewhere
in the middle (at SSN % buf_size) and continue to get used from
there, but there's no reason to start from the beginning.

Signed-off-by: Karl Beldan <karl.beldan@rivierawaves.com>
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index caecef870c0e44e3562cdc0a874bcfd233fc77a1..401f3c26e707444ea62e5600b5d9a19aebd34922 100644 (file)
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -729,9 +729,7 @@ static void ieee80211_release_reorder_frames(struct ieee80211_sub_if_data *sdata
        lockdep_assert_held(&tid_agg_rx->reorder_lock);
 
        while (ieee80211_sn_less(tid_agg_rx->head_seq_num, head_seq_num)) {
-               index = ieee80211_sn_sub(tid_agg_rx->head_seq_num,
-                                        tid_agg_rx->ssn) %
-                                                       tid_agg_rx->buf_size;
+               index = tid_agg_rx->head_seq_num % tid_agg_rx->buf_size;
                ieee80211_release_reorder_frame(sdata, tid_agg_rx, index,
                                                frames);
        }
@@ -757,8 +755,7 @@ static void ieee80211_sta_reorder_release(struct ieee80211_sub_if_data *sdata,
        lockdep_assert_held(&tid_agg_rx->reorder_lock);
 
        /* release the buffer until next missing frame */
-       index = ieee80211_sn_sub(tid_agg_rx->head_seq_num,
-                                tid_agg_rx->ssn) % tid_agg_rx->buf_size;
+       index = tid_agg_rx->head_seq_num % tid_agg_rx->buf_size;
        if (!tid_agg_rx->reorder_buf[index] &&
            tid_agg_rx->stored_mpdu_num) {
                /*
@@ -793,15 +790,11 @@ static void ieee80211_sta_reorder_release(struct ieee80211_sub_if_data *sdata,
        } else while (tid_agg_rx->reorder_buf[index]) {
                ieee80211_release_reorder_frame(sdata, tid_agg_rx, index,
                                                frames);
-               index = ieee80211_sn_sub(tid_agg_rx->head_seq_num,
-                                        tid_agg_rx->ssn) %
-                                                       tid_agg_rx->buf_size;
+               index = tid_agg_rx->head_seq_num % tid_agg_rx->buf_size;
        }
 
        if (tid_agg_rx->stored_mpdu_num) {
-               j = index = ieee80211_sn_sub(tid_agg_rx->head_seq_num,
-                                            tid_agg_rx->ssn) %
-                                                       tid_agg_rx->buf_size;
+               j = index = tid_agg_rx->head_seq_num % tid_agg_rx->buf_size;
 
                for (; j != (index - 1) % tid_agg_rx->buf_size;
                     j = (j + 1) % tid_agg_rx->buf_size) {
@@ -861,8 +854,7 @@ static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_sub_if_data *sdata
 
        /* Now the new frame is always in the range of the reordering buffer */
 
-       index = ieee80211_sn_sub(mpdu_seq_num,
-                                tid_agg_rx->ssn) % tid_agg_rx->buf_size;
+       index = mpdu_seq_num % tid_agg_rx->buf_size;
 
        /* check if we already stored this frame */
        if (tid_agg_rx->reorder_buf[index]) {