Hi, Tejun! 在 2024/08/31 3:37, Tejun Heo 写道:
Hello, Haifeng. On Wed, Aug 28, 2024 at 11:32:24AM +0800, Haifeng Xu wrote: ...The filesystem is ext4(ordered). The meta data can be written out by writeback, but if there are too many dirty pages, we had to do checkpoint to write out the meta data in current thread context. In this case, the blkg of thread1 has set io.max, so the j_checkpoint_mutex can't be released and many threads must wait for it. However, the blkg from buffer page didn' set any io policy. Therefore, for the meta buffer head, we can associate the bio with blkg from the buffer page instead of current thread context. Signed-off-by: Haifeng Xu <haifeng.xu@xxxxxxxxxx> --- fs/buffer.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/buffer.c b/fs/buffer.c index e55ad471c530..a7889f258d0d 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2819,6 +2819,17 @@ static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh, if (wbc) { wbc_init_bio(wbc, bio); wbc_account_cgroup_owner(wbc, bh->b_page, bh->b_size); + } 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 think the right way to do it is marking the bio with REQ_META and implement forced charging in blk-throtl similar to blk-iocost.
This is the exact thing I did in the code I attached in the other thread, do you take a look? https://lore.kernel.org/all/97fc38e6-a226-5e22-efc2-4405beb6d75b@xxxxxxxxxxxxxxx/ Thanks, Kuai
Thanks.
