Messages in this thread Patch in this message | | | Date | Thu, 21 Dec 2023 12:58:13 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH v9 1/2] ring-buffer: Introducing ring-buffer mapping functions |
| |
On Thu, 21 Dec 2023 17:35:22 +0000 Vincent Donnefort <vdonnefort@google.com> wrote:
> @@ -5999,6 +6078,307 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) > } > EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set); >
The kernel developers have agreed to allow loop variables to be declared in loops. This will simplify these macros:
> +#define subbuf_page(off, start) \ > + virt_to_page((void *)(start + (off << PAGE_SHIFT))) > + > +#define foreach_subbuf_page(off, sub_order, start, page) \ > + for (off = 0, page = subbuf_page(0, start); \ > + off < (1 << sub_order); \ > + off++, page = subbuf_page(off, start))
#define foreach_subbuf_page(sub_order, start, page) \ for (int __off = 0, page = subbuf_page(0, (start)); \ __off < (1 << (sub_order)); \ __off++, page = subbuf_page(__off, (start)))
And parameters as r-values should always be wrapped in parenthesis. > + > +static inline void subbuf_map_prepare(unsigned long subbuf_start, int order) > +{ > + struct page *page; > + int subbuf_off;
Then you can remove the "subbuf_off".
> + > + /* > + * When allocating order > 0 pages, only the first struct page has a > + * refcount > 1. Increasing the refcount here ensures none of the struct > + * page composing the sub-buffer is freeed when the mapping is closed.
Nice catch by the way ;-)
-- Steve
> + */ > + foreach_subbuf_page(subbuf_off, order, subbuf_start, page) > + page_ref_inc(page); > +} > + > +static inline void subbuf_unmap(unsigned long subbuf_start, int order) > +{ > + struct page *page; > + int subbuf_off; > + > + foreach_subbuf_page(subbuf_off, order, subbuf_start, page) { > + page_ref_dec(page); > + page->mapping = NULL; > + } > +} > +
| |