From: "Steven Rostedt (Google)" <rost...@goodmis.org> In preparation for having the ring buffer mapped to a dedicated location, which will have the same restrictions as user space memory mapped buffers, allow it to use the "mapped" field of the ring_buffer_per_cpu structure without having the user space meta page mapping.
When this starts using the mapped field, it will need to handle adding a user space mapping (and removing it) from a ring buffer that is using a dedicated memory range. Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org> --- kernel/trace/ring_buffer.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 1d7d7a701867..524b2c185c88 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5171,6 +5171,9 @@ static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer) { struct trace_buffer_meta *meta = cpu_buffer->meta_page; + if (!meta) + return; + meta->reader.read = cpu_buffer->reader_page->read; meta->reader.id = cpu_buffer->reader_page->id; meta->reader.lost_events = cpu_buffer->lost_events; @@ -6159,7 +6162,7 @@ rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu) mutex_lock(&cpu_buffer->mapping_lock); - if (!cpu_buffer->mapped) { + if (!cpu_buffer->mapped || !cpu_buffer->meta_page) { mutex_unlock(&cpu_buffer->mapping_lock); return ERR_PTR(-ENODEV); } @@ -6217,7 +6220,7 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu) mutex_lock(&cpu_buffer->mapping_lock); - if (cpu_buffer->mapped) { + if (cpu_buffer->meta_page) { err = __rb_inc_dec_mapped(buffer, cpu_buffer, true); mutex_unlock(&cpu_buffer->mapping_lock); return err; @@ -6247,7 +6250,7 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu) raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_setup_ids_meta_page(cpu_buffer, subbuf_ids); - cpu_buffer->mapped = 1; + cpu_buffer->mapped++; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); unlock: -- 2.43.0