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ring-buffer: Remove ring_buffer_per_cpu::mapped

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ring_buffer_per_cpu::mapped tracks if a ring-buffer is either mapped by
user-space or if it is a persistent buffer. We already have user_mapped
for the former and ring_meta for the latter. Get rid of mapped and
instead create rb_is_static(). A static ring-buffer cannot be resized,
swapped or have its pages extracted.

Link: https://patch.msgid.link/20260813131152.3589632-10-vdonnefort@google.com
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Vincent Donnefort
2026-08-13 14:11:51 +01:00
committed by Steven Rostedt
parent d9b5e22bf2
commit 8b502bf6eb
1 changed files with 17 additions and 28 deletions
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45
kernel/trace/ring_buffer.c
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@@ -514,7 +514,7 @@ struct ring_buffer_per_cpu {
int cpu;
atomic_t record_disabled;
atomic_t resize_disabled;
struct trace_buffer *buffer;
struct trace_buffer *buffer;
raw_spinlock_t reader_lock; /* serialize readers */
arch_spinlock_t lock;
struct lock_class_key lock_key;
@@ -552,7 +552,6 @@ struct ring_buffer_per_cpu {
/* pages removed since last reset */
unsigned long pages_removed;
unsigned int mapped;
unsigned int user_mapped; /* user space mapping */
struct mutex mapping_lock;
struct buffer_page **subbuf_ids; /* ID to subbuf VA */
@@ -648,6 +647,11 @@ unsigned long rb_subbuf_start(struct trace_buffer *buffer, unsigned long addr)
return addr & ~((unsigned long)(rb_subbuf_size(buffer) - 1));
}
static bool rb_is_static(struct ring_buffer_per_cpu *cpu_buffer)
{
return cpu_buffer->user_mapped || cpu_buffer->remote || cpu_buffer->ring_meta;
}
struct ring_buffer_iter {
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long head;
@@ -2578,7 +2582,6 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
* Range mapped buffers have the same restrictions as memory
* mapped ones do.
*/
cpu_buffer->mapped = 1;
cpu_buffer->ring_meta = rb_range_meta(buffer, nr_pages, cpu);
bpage->page = rb_range_buffer(cpu_buffer, 0);
if (!bpage->page)
@@ -6667,12 +6670,11 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
rb_head_page_activate(cpu_buffer);
cpu_buffer->pages_removed = 0;
if (cpu_buffer->mapped) {
rb_update_meta_page(cpu_buffer);
if (cpu_buffer->ring_meta) {
struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
meta->commit_buffer = meta->head_buffer;
}
rb_update_meta_page(cpu_buffer);
if (cpu_buffer->ring_meta) {
struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
meta->commit_buffer = meta->head_buffer;
}
}
@@ -6921,8 +6923,8 @@ int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
cpu_buffer_a = buffer_a->buffers[cpu];
cpu_buffer_b = buffer_b->buffers[cpu];
/* It's up to the callers to not try to swap mapped buffers */
if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped))
/* It's up to the callers to not try to swap static buffers */
if (WARN_ON_ONCE(rb_is_static(cpu_buffer_a) || rb_is_static(cpu_buffer_b)))
return -EBUSY;
/* At least make sure the two buffers are somewhat the same */
@@ -7134,7 +7136,6 @@ int ring_buffer_read_page(struct trace_buffer *buffer,
unsigned int size;
unsigned int read;
u64 save_timestamp;
bool force_memcpy;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return -1;
@@ -7173,8 +7174,6 @@ int ring_buffer_read_page(struct trace_buffer *buffer,
/* Check if any events were dropped */
missed_events = cpu_buffer->lost_events;
force_memcpy = cpu_buffer->mapped || cpu_buffer->remote;
/*
* If this page has been partially read or
* if len is not big enough to read the rest of the page or
@@ -7184,7 +7183,7 @@ int ring_buffer_read_page(struct trace_buffer *buffer,
*/
if (read || (len < (size - read)) ||
cpu_buffer->reader_page == cpu_buffer->commit_page ||
force_memcpy) {
rb_is_static(cpu_buffer)) {
struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
unsigned int rpos = read;
unsigned int pos = 0;
@@ -7633,11 +7632,7 @@ static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer,
lockdep_assert_held(&cpu_buffer->mapping_lock);
/* mapped is always greater or equal to user_mapped */
if (WARN_ON(cpu_buffer->mapped < cpu_buffer->user_mapped))
return -EINVAL;
if (inc && cpu_buffer->mapped == UINT_MAX)
if (inc && cpu_buffer->user_mapped == UINT_MAX)
return -EBUSY;
if (WARN_ON(!inc && cpu_buffer->user_mapped == 0))
@@ -7646,13 +7641,10 @@ static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer,
mutex_lock(&cpu_buffer->buffer->mutex);
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
if (inc) {
if (inc)
cpu_buffer->user_mapped++;
cpu_buffer->mapped++;
} else {
else
cpu_buffer->user_mapped--;
cpu_buffer->mapped--;
}
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
mutex_unlock(&cpu_buffer->buffer->mutex);
@@ -7824,7 +7816,6 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu,
if (!err) {
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/* This is the first time it is mapped by user */
cpu_buffer->mapped++;
cpu_buffer->user_mapped = 1;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
} else {
@@ -7881,8 +7872,6 @@ int ring_buffer_unmap(struct trace_buffer *buffer, int cpu)
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/* This is the last user space mapping */
if (!WARN_ON_ONCE(cpu_buffer->mapped < cpu_buffer->user_mapped))
cpu_buffer->mapped--;
cpu_buffer->user_mapped = 0;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);