Re: [PATCH] buffer: Associate the meta bio with blkg from buffer page
From: Christoph Hellwig <hch@infradead.org>
Date: 2024-08-28 05:19:40
Also in:
linux-block, linux-fsdevel, lkml
On Wed, Aug 28, 2024 at 11:32:24AM +0800, Haifeng Xu wrote:
+ } else if (buffer_meta(bh)) {
+ struct folio *folio;
+ struct cgroup_subsys_state *memcg_css, *blkcg_css;
+
+ folio = page_folio(bh->b_page);
+ memcg_css = mem_cgroup_css_from_folio(folio);
+ if (cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
+ cgroup_subsys_on_dfl(io_cgrp_subsys)) {
+ blkcg_css = cgroup_e_css(memcg_css->cgroup, &io_cgrp_subsys);
+ bio_associate_blkg_from_css(bio, blkcg_css);
+ }I'll leave it to people more familiar with cgroups to decide if this is the right thing to do, but if it is the code here should go into a helper so that other metadata bio submitters can reuse it. That helper also should have a good comment explaining it.