Patch "tracing: Set actual size after ring buffer resize" 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

    tracing: Set actual size after ring buffer resize

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:
     tracing-set-actual-size-after-ring-buffer-resize.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 175023fde4b0ed08e81335c40052bfc18da0dbd9
Author: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
Date:   Wed Jul 5 08:27:05 2023 +0800

    tracing: Set actual size after ring buffer resize
    
    [ Upstream commit 6d98a0f2ac3c021d21be66fa34e992137cd25bcb ]
    
    Currently we can resize trace ringbuffer by writing a value into file
    'buffer_size_kb', then by reading the file, we get the value that is
    usually what we wrote. However, this value may be not actual size of
    trace ring buffer because of the round up when doing resize in kernel,
    and the actual size would be more useful.
    
    Link: https://lore.kernel.org/linux-trace-kernel/20230705002705.576633-1-zhengyejian1@xxxxxxxxxx
    
    Cc: <mhiramat@xxxxxxxxxx>
    Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
    Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
    Stable-dep-of: d78ab792705c ("tracing: Stop current tracer when resizing buffer")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dc35f9150af7a..049daa6a9ad42 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6190,6 +6190,15 @@ static void set_buffer_entries(struct array_buffer *buf, unsigned long val)
 		per_cpu_ptr(buf->data, cpu)->entries = val;
 }
 
+static void update_buffer_entries(struct array_buffer *buf, int cpu)
+{
+	if (cpu == RING_BUFFER_ALL_CPUS) {
+		set_buffer_entries(buf, ring_buffer_size(buf->buffer, 0));
+	} else {
+		per_cpu_ptr(buf->data, cpu)->entries = ring_buffer_size(buf->buffer, cpu);
+	}
+}
+
 #ifdef CONFIG_TRACER_MAX_TRACE
 /* resize @tr's buffer to the size of @size_tr's entries */
 static int resize_buffer_duplicate_size(struct array_buffer *trace_buf,
@@ -6267,18 +6276,12 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
 		return ret;
 	}
 
-	if (cpu == RING_BUFFER_ALL_CPUS)
-		set_buffer_entries(&tr->max_buffer, size);
-	else
-		per_cpu_ptr(tr->max_buffer.data, cpu)->entries = size;
+	update_buffer_entries(&tr->max_buffer, cpu);
 
  out:
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
-	if (cpu == RING_BUFFER_ALL_CPUS)
-		set_buffer_entries(&tr->array_buffer, size);
-	else
-		per_cpu_ptr(tr->array_buffer.data, cpu)->entries = size;
+	update_buffer_entries(&tr->array_buffer, cpu);
 
 	return ret;
 }