linux-kernel - [PATCH v2] ring-buffer: Add rb_check_bpage in __rb_allocate

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Message-Id: <20201015113842.2921-1-hqjagain@gmail.com>
Date:   Thu, 15 Oct 2020 19:38:42 +0800
From:   Qiujun Huang <hqjagain@...il.com>
To:     rostedt@...dmis.org, mingo@...hat.com, linux-kernel@...r.kernel.org
Cc:     Qiujun Huang <hqjagain@...il.com>
Subject: [PATCH v2] ring-buffer: Add rb_check_bpage in __rb_allocate_pages

It may be better to check each page is aligned by 4 bytes. The 2
least significant bits of the address will be used as flags.

Signed-off-by: Qiujun Huang <hqjagain@...il.com>
---
v2:
remove passing the int cpu to __rb_allocate_pages.
---
 kernel/trace/ring_buffer.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 93ef0ab6ea20..b2c6f2546d69 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1420,7 +1420,8 @@ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
 	return 0;
 }
 
-static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
+static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
+		long nr_pages, struct list_head *pages)
 {
 	struct buffer_page *bpage, *tmp;
 	bool user_thread = current->mm != NULL;
@@ -1460,13 +1461,15 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
 		struct page *page;
 
 		bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
-				    mflags, cpu_to_node(cpu));
+				    mflags, cpu_to_node(cpu_buffer->cpu));
 		if (!bpage)
 			goto free_pages;
 
+		rb_check_bpage(cpu_buffer, bpage);
+
 		list_add(&bpage->list, pages);
 
-		page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
+		page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags, 0);
 		if (!page)
 			goto free_pages;
 		bpage->page = page_address(page);
@@ -1498,7 +1501,7 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 
 	WARN_ON(!nr_pages);
 
-	if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
+	if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
 		return -ENOMEM;
 
 	/*
@@ -2007,8 +2010,8 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
 			 * allocated without receiving ENOMEM
 			 */
 			INIT_LIST_HEAD(&cpu_buffer->new_pages);
-			if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
-						&cpu_buffer->new_pages, cpu)) {
+			if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
+						&cpu_buffer->new_pages)) {
 				/* not enough memory for new pages */
 				err = -ENOMEM;
 				goto out_err;
@@ -2073,8 +2076,8 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
 
 		INIT_LIST_HEAD(&cpu_buffer->new_pages);
 		if (cpu_buffer->nr_pages_to_update > 0 &&
-			__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
-					    &cpu_buffer->new_pages, cpu_id)) {
+			__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
+					    &cpu_buffer->new_pages)) {
 			err = -ENOMEM;
 			goto out_err;
 		}
-- 
2.17.1