[for-linus][PATCH 15/16] ring-buffer: Use subbuf_order in available memory estimation

[Steven Rostedt <rostedt@kernel.org>]

From: Vincent Donnefort <vdonnefort@google.com>

To avoid failing in the middle of an allocation of a ring-buffer,
__rb_allocate_pages() looks at the available memory estimation with
si_mem_available(). Use the subbuffer order with this estimation to fail
early if necessary for ring-buffers with an order > 0.

Link: https://patch.msgid.link/20261013102047.1488347-3-vdonnefort@google.com
Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page")
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index cbf67183c2e7..9c4e40847e43 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2443,6 +2443,7 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 			       unsigned long nr_pages, struct list_head *pages)
 {
 	struct trace_buffer *buffer = cpu_buffer->buffer;
+	unsigned int subbuf_order = buffer->subbuf_order;
 	struct ring_buffer_cpu_meta *meta = NULL;
 	struct buffer_page *bpage, *tmp;
 	struct ring_buffer_desc *desc = NULL;
@@ -2464,7 +2465,7 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 		 * not going to succeed.
 		 */
 		i = si_mem_available();
-		if (i < nr_pages)
+		if (i < (nr_pages << subbuf_order))
 			return -ENOMEM;
 
 		user_thread = current->mm != NULL;
@@ -2517,12 +2518,11 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 			bpage->id = i + 1;
 			cpu_buffer->subbuf_ids[i + 1] = bpage;
 		} else {
-			bpage->page = alloc_cpu_data(cpu_buffer->cpu,
-						     cpu_buffer->buffer->subbuf_order);
+			bpage->page = alloc_cpu_data(cpu_buffer->cpu, subbuf_order);
 			if (!bpage->page)
 				goto free_pages;
 		}
-		bpage->order = cpu_buffer->buffer->subbuf_order;
+		bpage->order = subbuf_order;
 
 		if (user_thread && fatal_signal_pending(current))
 			goto free_pages;
-- 
2.53.0