Commit 4e958db3 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

ring-buffer: Make sure the spare sub buffer used for reads has same size 

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.

Link: https://lore.kernel.org/linux-trace-kernel/20231219185629.763664788@goodmis.org



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent b81e03a2

kernel/trace/trace.c

+11 −0
Original line number Diff line number Diff line
@@ -7582,6 +7582,7 @@ struct ftrace_buffer_info { 
	struct trace_iterator	iter;

	void			*spare;

	unsigned int		spare_cpu;

	unsigned int		spare_size;

	unsigned int		read;

};
@@ -8301,6 +8302,15 @@ 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);
@@ -8309,6 +8319,7 @@ 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)