From c9fc60c18b6d42efdea0cd88ca132b2f452157c3 Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Tue, 13 Oct 2026 11:20:46 +0100 Subject: [PATCH] ring-buffer: Skip si_mem_available() for persistent and remote buffers Persistent and remote buffer memory is pre-allocated by the time __rb_allocate_pages() is called. Skip si_mem_available() to avoid wrongly failing the allocation under memory pressure. For the same reason, unset user_thread. Link: https://patch.msgid.link/20261013102047.1488347-2-vdonnefort@google.com Fixes: be68d63a139b ("ring-buffer: Add ring_buffer_alloc_range()") Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes") Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 41 +++++++++++++++++++------------------- 1 file changed, 21 insertions(+), 20 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index e2b721d0707f..cbf67183c2e7 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2445,20 +2445,30 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, struct trace_buffer *buffer = cpu_buffer->buffer; struct ring_buffer_cpu_meta *meta = NULL; struct buffer_page *bpage, *tmp; - bool user_thread = current->mm != NULL; struct ring_buffer_desc *desc = NULL; + bool user_thread = false; long i; - /* - * Check if the available memory is there first. - * Note, si_mem_available() only gives us a rough estimate of available - * memory. It may not be accurate. But we don't care, we just want - * to prevent doing any allocation when it is obvious that it is - * not going to succeed. - */ - i = si_mem_available(); - if (i < nr_pages) - return -ENOMEM; + if (buffer->range_addr_start) { + meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu); + } else if (buffer->remote) { + desc = ring_buffer_desc(buffer->remote->desc, cpu_buffer->cpu); + if (!desc || WARN_ON(desc->nr_page_va != (nr_pages + 1))) + return -EINVAL; + } else { + /* + * Check if the available memory is there first. + * Note, si_mem_available() only gives us a rough estimate of available + * memory. It may not be accurate. But we don't care, we just want + * to prevent doing any allocation when it is obvious that it is + * not going to succeed. + */ + i = si_mem_available(); + if (i < nr_pages) + return -ENOMEM; + + user_thread = current->mm != NULL; + } /* * If a user thread allocates too much, and si_mem_available() @@ -2472,15 +2482,6 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, if (user_thread) set_current_oom_origin(); - if (buffer->range_addr_start) - meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu); - - if (buffer->remote) { - desc = ring_buffer_desc(buffer->remote->desc, cpu_buffer->cpu); - if (!desc || WARN_ON(desc->nr_page_va != (nr_pages + 1))) - return -EINVAL; - } - for (i = 0; i < nr_pages; i++) { bpage = alloc_cpu_page(cpu_buffer->cpu);