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Commit e4c2ce82 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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ring_buffer: allocate buffer page pointer 



The current method of overlaying the page frame as the buffer page pointer
can be very dangerous and limits our ability to do other things with
a page from the buffer, like send it off to disk.

This patch allocates the buffer_page instead of overlaying the page's
page frame. The use of the buffer_page has hardly changed due to this.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 7104f300

kernel/trace/ring_buffer.c

+32 −22
Original line number Diff line number Diff line
@@ -115,16 +115,10 @@ void *ring_buffer_event_data(struct ring_buffer_event *event) 
 * Thanks to Peter Zijlstra for suggesting this idea.

 */

struct buffer_page {

	union {

		struct {

			unsigned long	 flags;		/* mandatory */

			atomic_t	 _count;	/* mandatory */

	u64		 time_stamp;	/* page time stamp */

	unsigned	 size;		/* size of page data */

	struct list_head list;		/* list of free pages */

		};

		struct page page;

	};

	void *page;			/* Actual data page */

};



/*
@@ -133,9 +127,9 @@ struct buffer_page { 
 */

static inline void free_buffer_page(struct buffer_page *bpage)

{

	reset_page_mapcount(&bpage->page);

	bpage->page.mapping = NULL;

	__free_page(&bpage->page);

	if (bpage->page)

		__free_page(bpage->page);

	kfree(bpage);

}



/*
@@ -237,11 +231,16 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, 
	unsigned i;



	for (i = 0; i < nr_pages; i++) {

		page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),

				    GFP_KERNEL, cpu_to_node(cpu));

		if (!page)

			goto free_pages;

		list_add(&page->list, &pages);



		addr = __get_free_page(GFP_KERNEL);

		if (!addr)

			goto free_pages;

		page = (struct buffer_page *)virt_to_page(addr);

		list_add(&page->list, &pages);

		page->page = (void *)addr;

	}



	list_splice(&pages, head);
@@ -262,6 +261,7 @@ static struct ring_buffer_per_cpu * 
rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)

{

	struct ring_buffer_per_cpu *cpu_buffer;

	struct buffer_page *page;

	unsigned long addr;

	int ret;
@@ -275,10 +275,17 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) 
	spin_lock_init(&cpu_buffer->lock);

	INIT_LIST_HEAD(&cpu_buffer->pages);



	page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),

			    GFP_KERNEL, cpu_to_node(cpu));

	if (!page)

		goto fail_free_buffer;



	cpu_buffer->reader_page = page;

	addr = __get_free_page(GFP_KERNEL);

	if (!addr)

		goto fail_free_buffer;

	cpu_buffer->reader_page = (struct buffer_page *)virt_to_page(addr);

		goto fail_free_reader;

	page->page = (void *)addr;



	INIT_LIST_HEAD(&cpu_buffer->reader_page->list);

	cpu_buffer->reader_page->size = 0;
@@ -523,11 +530,16 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) 


	for_each_buffer_cpu(buffer, cpu) {

		for (i = 0; i < new_pages; i++) {

			page = kzalloc_node(ALIGN(sizeof(*page),

						  cache_line_size()),

					    GFP_KERNEL, cpu_to_node(cpu));

			if (!page)

				goto free_pages;

			list_add(&page->list, &pages);

			addr = __get_free_page(GFP_KERNEL);

			if (!addr)

				goto free_pages;

			page = (struct buffer_page *)virt_to_page(addr);

			list_add(&page->list, &pages);

			page->page = (void *)addr;

		}

	}
@@ -567,9 +579,7 @@ static inline int rb_null_event(struct ring_buffer_event *event) 


static inline void *rb_page_index(struct buffer_page *page, unsigned index)

{

	void *addr = page_address(&page->page);



	return addr + index;

	return page->page + index;

}



static inline struct ring_buffer_event *