[PATCH] ring-buffer: Fix reader page read offset for remote buffers

[Vincent Donnefort]

A page swapped in by __rb_get_reader_page_from_remote() retains its
stale read offset, causing subsequent reads to skip events or read
past valid data. Fix it.

Fixes: fbd1743ecba1 ("ring-buffer: Add non-consuming read for ring-buffer 
remotes")
Signed-off-by: Vincent Donnefort <vdonnef...@google.com>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 804ccae694d2..78d3875a47a5 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5783,6 +5783,7 @@ __rb_get_reader_page_from_remote(struct 
ring_buffer_per_cpu *cpu_buffer)
 
        cpu_buffer->head_page = new_head;
        cpu_buffer->reader_page = new_reader;
+       cpu_buffer->reader_page->read = 0;
        cpu_buffer->pages = &new_head->list;
        cpu_buffer->read_stamp = new_reader->page->time_stamp;
        cpu_buffer->lost_events = cpu_buffer->meta_page->reader.lost_events;

base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff
-- 
2.55.0.487.gaf234c4eb3-goog