Patch "bpf: Use u64_stats_t in struct bpf_prog_stats" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    bpf: Use u64_stats_t in struct bpf_prog_stats

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-use-u64_stats_t-in-struct-bpf_prog_stats.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f3c6b4d11bc60342817719fa79759c3512196d38
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Tue Oct 26 14:41:33 2021 -0700

    bpf: Use u64_stats_t in struct bpf_prog_stats
    
    [ Upstream commit 61a0abaee2092eee69e44fe60336aa2f5b578938 ]
    
    Commit 316580b69d0a ("u64_stats: provide u64_stats_t type")
    fixed possible load/store tearing on 64bit arches.
    
    For instance the following C code
    
    stats->nsecs += sched_clock() - start;
    
    Could be rightfully implemented like this by a compiler,
    confusing concurrent readers a lot:
    
    stats->nsecs += sched_clock();
    // arbitrary delay
    stats->nsecs -= start;
    
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
    Link: https://lore.kernel.org/bpf/20211026214133.3114279-4-eric.dumazet@xxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 1611dc9d44207..a9956b681f090 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -554,9 +554,9 @@ struct bpf_binary_header {
 };
 
 struct bpf_prog_stats {
-	u64 cnt;
-	u64 nsecs;
-	u64 misses;
+	u64_stats_t cnt;
+	u64_stats_t nsecs;
+	u64_stats_t misses;
 	struct u64_stats_sync syncp;
 } __aligned(2 * sizeof(u64));
 
@@ -618,8 +618,8 @@ static __always_inline u32 __bpf_prog_run(const struct bpf_prog *prog,
 		ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
 		stats = this_cpu_ptr(prog->stats);
 		flags = u64_stats_update_begin_irqsave(&stats->syncp);
-		stats->cnt++;
-		stats->nsecs += sched_clock() - start;
+		u64_stats_inc(&stats->cnt);
+		u64_stats_add(&stats->nsecs, sched_clock() - start);
 		u64_stats_update_end_irqrestore(&stats->syncp, flags);
 	} else {
 		ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 53384622e8dac..42490c39dfbf5 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1824,8 +1824,14 @@ static int bpf_prog_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+struct bpf_prog_kstats {
+	u64 nsecs;
+	u64 cnt;
+	u64 misses;
+};
+
 static void bpf_prog_get_stats(const struct bpf_prog *prog,
-			       struct bpf_prog_stats *stats)
+			       struct bpf_prog_kstats *stats)
 {
 	u64 nsecs = 0, cnt = 0, misses = 0;
 	int cpu;
@@ -1838,9 +1844,9 @@ static void bpf_prog_get_stats(const struct bpf_prog *prog,
 		st = per_cpu_ptr(prog->stats, cpu);
 		do {
 			start = u64_stats_fetch_begin_irq(&st->syncp);
-			tnsecs = st->nsecs;
-			tcnt = st->cnt;
-			tmisses = st->misses;
+			tnsecs = u64_stats_read(&st->nsecs);
+			tcnt = u64_stats_read(&st->cnt);
+			tmisses = u64_stats_read(&st->misses);
 		} while (u64_stats_fetch_retry_irq(&st->syncp, start));
 		nsecs += tnsecs;
 		cnt += tcnt;
@@ -1856,7 +1862,7 @@ static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp)
 {
 	const struct bpf_prog *prog = filp->private_data;
 	char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
-	struct bpf_prog_stats stats;
+	struct bpf_prog_kstats stats;
 
 	bpf_prog_get_stats(prog, &stats);
 	bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
@@ -3595,7 +3601,7 @@ static int bpf_prog_get_info_by_fd(struct file *file,
 	struct bpf_prog_info __user *uinfo = u64_to_user_ptr(attr->info.info);
 	struct bpf_prog_info info;
 	u32 info_len = attr->info.info_len;
-	struct bpf_prog_stats stats;
+	struct bpf_prog_kstats stats;
 	char __user *uinsns;
 	u32 ulen;
 	int err;
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index d3a307a8c42b9..6933a9bfee637 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -544,7 +544,7 @@ static void notrace inc_misses_counter(struct bpf_prog *prog)
 
 	stats = this_cpu_ptr(prog->stats);
 	u64_stats_update_begin(&stats->syncp);
-	stats->misses++;
+	u64_stats_inc(&stats->misses);
 	u64_stats_update_end(&stats->syncp);
 }
 
@@ -589,8 +589,8 @@ static void notrace update_prog_stats(struct bpf_prog *prog,
 
 		stats = this_cpu_ptr(prog->stats);
 		flags = u64_stats_update_begin_irqsave(&stats->syncp);
-		stats->cnt++;
-		stats->nsecs += sched_clock() - start;
+		u64_stats_inc(&stats->cnt);
+		u64_stats_add(&stats->nsecs, sched_clock() - start);
 		u64_stats_update_end_irqrestore(&stats->syncp, flags);
 	}
 }