[PATCH v5 10/10] ring-buffer: Make nr_pages unsigned int

[Vincent Donnefort <vdonnefort@google.com>]

nr_pages is an int or unsigned int almost everywhere already. Also, all
the meta-data ring_buffer_desc, ring_buffer_cpu_meta and
trace_buffer_meta allowing to share information about the ring buffer
are already capping this value to 32-bits.

Make ring_buffer_per_cpu::nr_pages unsigned and align all the users to
it. As a side effect, this makes ring_buffer_per_cpu slightly smaller.

Where necessary, use unsigned long for the size to ensure
multiplications are not truncated to 32-bits.

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

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 79459c99ce9a..d9dcd6d4e7cc 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -519,7 +519,7 @@ struct ring_buffer_per_cpu {
 	arch_spinlock_t			lock;
 	struct lock_class_key		lock_key;
 	struct buffer_data_read_page	free_page;
-	unsigned long			nr_pages;
+	unsigned int			nr_pages;
 	unsigned int			current_context;
 	struct list_head		*pages;
 	/* pages generation counter, incremented when the list changes */
@@ -561,7 +561,7 @@ struct ring_buffer_per_cpu {
 	struct ring_buffer_remote	*remote;
 
 	/* ring buffer pages to update, > 0 to add, < 0 to remove */
-	long				nr_pages_to_update;
+	int				nr_pages_to_update;
 	struct list_head		new_pages; /* new pages to add */
 	struct work_struct		update_pages_work;
 	struct completion		update_done;
@@ -1669,7 +1669,7 @@ static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
  * This is used to help find the next per cpu subbuffer within a mapped range.
  */
 static unsigned long
-rb_range_align_subbuf(unsigned long addr, int subbuf_size, int nr_subbufs)
+rb_range_align_subbuf(unsigned long addr, unsigned long subbuf_size, unsigned int nr_subbufs)
 {
 	addr += sizeof(struct ring_buffer_cpu_meta) +
 		sizeof(int) * nr_subbufs;
@@ -1679,13 +1679,13 @@ rb_range_align_subbuf(unsigned long addr, int subbuf_size, int nr_subbufs)
 /*
  * Return the ring_buffer_meta for a given @cpu.
  */
-static void *rb_range_meta(struct trace_buffer *buffer, int nr_pages, int cpu)
+static void *rb_range_meta(struct trace_buffer *buffer, unsigned int nr_pages, int cpu)
 {
-	int subbuf_size = rb_subbuf_size(buffer);
+	unsigned long subbuf_size = rb_subbuf_size(buffer);
 	struct ring_buffer_cpu_meta *meta;
 	struct ring_buffer_meta *bmeta;
+	unsigned int nr_subbufs;
 	unsigned long ptr;
-	int nr_subbufs;
 
 	bmeta = buffer->meta;
 	if (!bmeta)
@@ -1731,7 +1731,7 @@ static void *rb_range_meta(struct trace_buffer *buffer, int nr_pages, int cpu)
 /* Return the start of subbufs given the meta pointer */
 static void *rb_subbufs_from_meta(struct ring_buffer_cpu_meta *meta)
 {
-	int subbuf_size = meta->subbuf_size;
+	unsigned long subbuf_size = meta->subbuf_size;
 	unsigned long ptr;
 
 	ptr = (unsigned long)meta;
@@ -1746,8 +1746,7 @@ static void *rb_subbufs_from_meta(struct ring_buffer_cpu_meta *meta)
 static void *rb_range_buffer(struct ring_buffer_per_cpu *cpu_buffer, int idx)
 {
 	struct ring_buffer_cpu_meta *meta;
-	unsigned long ptr;
-	int subbuf_size;
+	unsigned long subbuf_size, ptr;
 
 	meta = rb_range_meta(cpu_buffer->buffer, 0, cpu_buffer->cpu);
 	if (!meta)
@@ -1840,10 +1839,10 @@ static bool rb_meta_init(struct trace_buffer *buffer, int scratch_size)
  * must be the same.
  */
 static bool rb_cpu_meta_valid(struct ring_buffer_cpu_meta *meta, int cpu,
-			      struct trace_buffer *buffer, int nr_pages,
+			      struct trace_buffer *buffer, unsigned int nr_pages,
 			      unsigned long *subbuf_mask)
 {
-	int subbuf_size = PAGE_SIZE;
+	unsigned long subbuf_size = PAGE_SIZE;
 	unsigned long buffers_start;
 	unsigned long buffers_end;
 	int i;
@@ -2231,7 +2230,7 @@ static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer)
 	}
 }
 
-static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages, int scratch_size)
+static void rb_range_meta_init(struct trace_buffer *buffer, unsigned int nr_pages, int scratch_size)
 {
 	struct ring_buffer_cpu_meta *meta;
 	unsigned long *subbuf_mask;
@@ -2331,8 +2330,8 @@ static int rbm_show(struct seq_file *m, void *v)
 			   rb_meta_subbuf_idx(meta, (void *)meta->head_buffer));
 		seq_printf(m, "commit_buffer: %d\n",
 			   rb_meta_subbuf_idx(meta, (void *)meta->commit_buffer));
-		seq_printf(m, "subbuf_size:   %d\n", meta->subbuf_size);
-		seq_printf(m, "nr_subbufs:    %d\n", meta->nr_subbufs);
+		seq_printf(m, "subbuf_size:   %u\n", meta->subbuf_size);
+		seq_printf(m, "nr_subbufs:    %u\n", meta->nr_subbufs);
 		return 0;
 	}
 
@@ -2417,7 +2416,7 @@ static void *ring_buffer_desc_page(struct ring_buffer_desc *desc, unsigned int p
 }
 
 static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
-		long nr_pages, struct list_head *pages)
+			       unsigned int nr_pages, struct list_head *pages)
 {
 	struct trace_buffer *buffer = cpu_buffer->buffer;
 	struct ring_buffer_cpu_meta *meta = NULL;
@@ -2520,7 +2519,7 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 }
 
 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
-			     unsigned long nr_pages)
+			     unsigned int nr_pages)
 {
 	LIST_HEAD(pages);
 
@@ -2545,7 +2544,7 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 }
 
 static struct ring_buffer_per_cpu *
-rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
+rb_allocate_cpu_buffer(struct trace_buffer *buffer, unsigned int nr_pages, int cpu)
 {
 	struct ring_buffer_per_cpu *cpu_buffer __free(kfree) =
 		alloc_cpu_buffer(cpu);
@@ -2703,7 +2702,7 @@ static void rb_test_inject_invalid_pages(struct trace_buffer *buffer)
 	struct buffer_data_page *dpage;
 	unsigned long entry_bytes = 0;
 	unsigned long ptr;
-	int subbuf_size;
+	unsigned long subbuf_size;
 	int invalid = 0;
 	int cpu;
 	int i;
@@ -2773,8 +2772,8 @@ static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flags,
 					 struct ring_buffer_remote *remote)
 {
 	struct trace_buffer *buffer __free(kfree) = NULL;
-	long nr_pages;
-	int subbuf_size;
+	unsigned long subbuf_size;
+	unsigned int nr_pages;
 	int bsize;
 	int cpu;
 	int ret;
@@ -3037,12 +3036,12 @@ static inline unsigned long rb_page_write(struct buffer_page *bpage)
 }
 
 static bool
-rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
+rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
 {
 	struct list_head *tail_page, *to_remove, *next_page;
 	struct buffer_page *to_remove_page, *tmp_iter_page;
 	struct buffer_page *last_page, *first_page;
-	unsigned long nr_removed;
+	unsigned int nr_removed;
 	unsigned long head_bit;
 	int page_entries;
 
@@ -3264,7 +3263,7 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
 			int cpu_id)
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
-	unsigned long nr_pages;
+	unsigned int nr_pages;
 	int cpu, err;
 
 	/*
@@ -4229,7 +4228,7 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
 	 * assign the commit to the tail.
 	 */
  again:
-	max_count = cpu_buffer->nr_pages * 100;
+	max_count = cpu_buffer->nr_pages * 100UL;
 
 	while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
 		if (RB_WARN_ON(cpu_buffer, !(--max_count)))
@@ -6522,7 +6521,7 @@ unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
 	if (!cpumask_test_cpu(cpu, buffer->cpumask))
 		return 0;
 
-	return rb_subbuf_capacity(buffer) * buffer->buffers[cpu]->nr_pages;
+	return (unsigned long)rb_subbuf_capacity(buffer) * buffer->buffers[cpu]->nr_pages;
 }
 EXPORT_SYMBOL_GPL(ring_buffer_size);
 
@@ -7418,8 +7417,8 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
 	struct ring_buffer_per_cpu *cpu_buffer;
 	struct buffer_page *bpage, *tmp;
 	unsigned int old_capacity;
+	unsigned int nr_pages;
 	int old_order;
-	int nr_pages;
 	int psize;
 	int err;
 	int cpu;
@@ -7465,8 +7464,9 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
 		}
 
 		/* Update the number of pages to match the new size */
-		nr_pages = old_capacity * buffer->buffers[cpu]->nr_pages;
-		nr_pages = DIV_ROUND_UP(nr_pages, rb_subbuf_capacity(buffer));
+		nr_pages = DIV_ROUND_UP(
+			(unsigned long)old_capacity * buffer->buffers[cpu]->nr_pages,
+			rb_subbuf_capacity(buffer));
 
 		/* we need a minimum of two pages */
 		if (nr_pages < 2)
@@ -7708,8 +7708,8 @@ static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer,
 static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
 			struct vm_area_struct *vma)
 {
-	unsigned long nr_subbufs, nr_pages, nr_vma_pages, pgoff = vma->vm_pgoff;
-	unsigned int subbuf_pages, subbuf_order;
+	unsigned long nr_pages, nr_vma_pages, pgoff = vma->vm_pgoff;
+	unsigned int nr_subbufs, subbuf_pages, subbuf_order;
 	struct page **pages __free(kfree) = NULL;
 	int p = 0, s = 0;
 	int err;
@@ -8039,9 +8039,9 @@ static void rb_cpu_sync(void *data)
 int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
 {
 	struct trace_buffer *buffer;
-	long nr_pages_same;
+	unsigned int nr_pages;
+	int nr_pages_same;
 	int cpu_i;
-	unsigned long nr_pages;
 
 	buffer = container_of(node, struct trace_buffer, node);
 	if (cpumask_test_cpu(cpu, buffer->cpumask))
-- 
2.55.0.691.gc56d675ccc-goog