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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Tzvetomir Stoyanov <tz.stoyanov@gmail.com>,
	Vincent Donnefort <vdonnefort@google.com>,
	Kent Overstreet <kent.overstreet@gmail.com>
Subject: [PATCH 08/14] ring-buffer: Make sure the spare sub buffer used for reads has same size
Date: Sat, 09 Dec 2023 22:54:12 -0500	[thread overview]
Message-ID: <20231210040450.561181051@goodmis.org> (raw)
In-Reply-To: 20231210035404.053677508@goodmis.org

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Now that the ring buffer specifies the size of its sub buffers, they all
need to be the same size. When doing a read, a swap is done with a spare
page. Make sure they are the same size before doing the swap, otherwise
the read will fail.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8e9853d38c8d..b3b36d7f1201 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7567,6 +7567,7 @@ struct ftrace_buffer_info {
 	struct trace_iterator	iter;
 	void			*spare;
 	unsigned int		spare_cpu;
+	unsigned int		spare_size;
 	unsigned int		read;
 };
 
@@ -8286,6 +8287,15 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
 
 	page_size = ring_buffer_subbuf_size_get(iter->array_buffer->buffer);
 
+	/* Make sure the spare matches the current sub buffer size */
+	if (info->spare) {
+		if (page_size != info->spare_size) {
+			ring_buffer_free_read_page(iter->array_buffer->buffer,
+						   info->spare_cpu, info->spare);
+			info->spare = NULL;
+		}
+	}
+
 	if (!info->spare) {
 		info->spare = ring_buffer_alloc_read_page(iter->array_buffer->buffer,
 							  iter->cpu_file);
@@ -8294,6 +8304,7 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
 			info->spare = NULL;
 		} else {
 			info->spare_cpu = iter->cpu_file;
+			info->spare_size = page_size;
 		}
 	}
 	if (!info->spare)
-- 
2.42.0



  parent reply	other threads:[~2023-12-10  4:04 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-10  3:54 [PATCH 00/14] ring-buffer/tracing: Allow ring buffer to have bigger sub buffers Steven Rostedt
2023-12-10  3:54 ` [PATCH 01/14] ring-buffer: Refactor ring buffer implementation Steven Rostedt
2023-12-10  3:54 ` [PATCH 02/14] ring-buffer: Page size per ring buffer Steven Rostedt
2023-12-10  3:54 ` [PATCH 03/14] ring-buffer: Add interface for configuring trace sub buffer size Steven Rostedt
2023-12-10  3:54 ` [PATCH 04/14] ring-buffer: Set new size of the ring buffer sub page Steven Rostedt
2023-12-10  3:54 ` [PATCH 05/14] ring-buffer: Read and write to ring buffers with custom sub buffer size Steven Rostedt
2023-12-10  3:54 ` [PATCH 06/14] ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure Steven Rostedt
2023-12-10  3:54 ` [PATCH 07/14] ring-buffer: Do no swap cpu buffers if order is different Steven Rostedt
2023-12-10  3:54 ` Steven Rostedt [this message]
2023-12-10  3:54 ` [PATCH 09/14] tracing: Update snapshot order along with main buffer order Steven Rostedt
2023-12-10  3:54 ` [PATCH 10/14] tracing: Stop the tracing while changing the ring buffer subbuf size Steven Rostedt
2023-12-10  3:54 ` [PATCH 11/14] ring-buffer: Keep the same size when updating the order Steven Rostedt
2023-12-10  3:54 ` [PATCH 12/14] ring-buffer: Just update the subbuffers when changing their allocation order Steven Rostedt
2023-12-10  3:54 ` [PATCH 13/14] ring-buffer: Add documentation on the buffer_subbuf_order file Steven Rostedt
2023-12-10 14:28   ` Mathieu Desnoyers
2023-12-10  3:54 ` [PATCH 14/14] ringbuffer/selftest: Add basic selftest to test chaning subbuf order Steven Rostedt
2023-12-10 14:26   ` Mathieu Desnoyers
2023-12-10 15:44     ` Steven Rostedt
2023-12-10 14:17 ` [PATCH 00/14] ring-buffer/tracing: Allow ring buffer to have bigger sub buffers Mathieu Desnoyers
2023-12-10 15:38   ` Steven Rostedt

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