On Mon, Mar 22, 2021 at 01:19:07AM +0000, Matthew Wilcox wrote:
> I'd like to get it down to zero. After all, the !mapping case in
> set_page_dirty() is exactly what we want. So is there a problem
> with doing this?
>
> +++ b/mm/page-writeback.c
> @@ -2562 +2562 @@ int set_page_dirty(struct page *page)
> - if (likely(mapping)) {
> + if (likely(mapping && mapping_can_writeback(mapping))) {
>
> But then I noticed that we have both mapping_can_writeback()
> and mapping_use_writeback_tags(), and I'm no longer sure
> which one to use. Also, why don't we mirror the results of
> inode_to_bdi(mapping->host)->capabilities & BDI_CAP_WRITEBACK into
> a mapping->flags & AS_something bit?
Probably because no one has bothered to submit a patch yet.
