Merge branch 'u64_stats-fixups'

Sebastian Andrzej Siewior says:

====================
net: u64_stats fixups for 32bit.

while looking at the u64-stats patch
	https://lore.kernel.org/all/20220817162703.728679-10-bigeasy@linutronix.de

I noticed that u64_stats_fetch_begin() is used. That suspicious thing
about it is that network processing, including stats update, is
performed in NAPI and so I would expect to see
u64_stats_fetch_begin_irq() in order to avoid updates from NAPI during
the read. This is only needed on 32bit-UP where the seqcount is not
used. This is address in 2/2. The remaining user take some kind of
precaution and may use u64_stats_fetch_begin().

I updated the previously mentioned patch to get rid of
u64_stats_fetch_begin_irq(). If this is not considered stable patch
worthy then it can be ignored and considred fixed by the other series
which removes the special 32bit cases.

The xrs700x driver reads and writes the counter from preemptible context
so the only missing piece here is at least disable preemption on the
writer side to avoid preemption while the writer is in progress. The
possible reader would spin then until the writer completes its write
critical section which is considered bad. This is addressed in 1/2 by
using u64_stats_update_begin_irqsave() and so disable interrupts during
the write critical section.
The other closet resemblance I found is mdio_bus.c::mdiobus_stats_acct()
where preemtion is disabled unconditionally. This is something I want to
avoid since it also affects 64bit.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 6 insertions, 6 deletions

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 330dab41f2fe..58998d821778 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -2316,9 +2316,9 @@ static inline u64 sta_get_tidstats_msdu(struct ieee80211_sta_rx_stats *rxstats,
 	u64 value;
 
 	do {
-		start = u64_stats_fetch_begin(&rxstats->syncp);
+		start = u64_stats_fetch_begin_irq(&rxstats->syncp);
 		value = rxstats->msdu[tid];
-	} while (u64_stats_fetch_retry(&rxstats->syncp, start));
+	} while (u64_stats_fetch_retry_irq(&rxstats->syncp, start));
 
 	return value;
 }
@@ -2384,9 +2384,9 @@ static inline u64 sta_get_stats_bytes(struct ieee80211_sta_rx_stats *rxstats)
 	u64 value;
 
 	do {
-		start = u64_stats_fetch_begin(&rxstats->syncp);
+		start = u64_stats_fetch_begin_irq(&rxstats->syncp);
 		value = rxstats->bytes;
-	} while (u64_stats_fetch_retry(&rxstats->syncp, start));
+	} while (u64_stats_fetch_retry_irq(&rxstats->syncp, start));
 
 	return value;
 }
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 35b5f806fdda..b52afe316dc4 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -1079,9 +1079,9 @@ static void mpls_get_stats(struct mpls_dev *mdev,
 
 		p = per_cpu_ptr(mdev->stats, i);
 		do {
-			start = u64_stats_fetch_begin(&p->syncp);
+			start = u64_stats_fetch_begin_irq(&p->syncp);
 			local = p->stats;
-		} while (u64_stats_fetch_retry(&p->syncp, start));
+		} while (u64_stats_fetch_retry_irq(&p->syncp, start));
 
 		stats->rx_packets	+= local.rx_packets;
 		stats->rx_bytes		+= local.rx_bytes;