linux-kernel - [PATCH v22 1/5] ring-buffer: Allocate sub-buffers with __GFP

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Date: Tue, 30 Apr 2024 12:13:50 +0100
From: Vincent Donnefort <vdonnefort@...gle.com>
To: rostedt@...dmis.org, mhiramat@...nel.org, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Cc: mathieu.desnoyers@...icios.com, kernel-team@...roid.com, 
	rdunlap@...radead.org, rppt@...nel.org, david@...hat.com, 
	Vincent Donnefort <vdonnefort@...gle.com>
Subject: [PATCH v22 1/5] ring-buffer: Allocate sub-buffers with __GFP_COMP

In preparation for the ring-buffer memory mapping, allocate compound
pages for the ring-buffer sub-buffers to enable us to map them to
user-space with vm_insert_pages().

Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 25476ead681b..cc9ebe593571 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1524,7 +1524,7 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 		list_add(&bpage->list, pages);
 
 		page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
-					mflags | __GFP_ZERO,
+					mflags | __GFP_COMP | __GFP_ZERO,
 					cpu_buffer->buffer->subbuf_order);
 		if (!page)
 			goto free_pages;
@@ -1609,7 +1609,7 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
 
 	cpu_buffer->reader_page = bpage;
 
-	page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_ZERO,
+	page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_COMP | __GFP_ZERO,
 				cpu_buffer->buffer->subbuf_order);
 	if (!page)
 		goto fail_free_reader;
@@ -5579,7 +5579,7 @@ ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
 		goto out;
 
 	page = alloc_pages_node(cpu_to_node(cpu),
-				GFP_KERNEL | __GFP_NORETRY | __GFP_ZERO,
+				GFP_KERNEL | __GFP_NORETRY | __GFP_COMP | __GFP_ZERO,
 				cpu_buffer->buffer->subbuf_order);
 	if (!page) {
 		kfree(bpage);
-- 
2.44.0.769.g3c40516874-goog