Re: [PATCH 05/13] swap,blkcg: issue swap io with the appropriate context
From: Tejun Heo <tj@kernel.org>
Date: 2018-05-30 16:05:27
Also in:
linux-fsdevel, linux-mm, lkml
On Tue, May 29, 2018 at 05:17:16PM -0400, Josef Bacik wrote:
quoted hunk ↗ jump to hunk
From: Tejun Heo <tj@kernel.org> For backcharging we need to know who the page belongs to when swapping it out. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Josef Bacik <redacted> --- mm/page_io.c | 10 ++++++++++ 1 file changed, 10 insertions(+)diff --git a/mm/page_io.c b/mm/page_io.c index a552cb37e220..61e1268e5dbc 100644 --- a/mm/page_io.c +++ b/mm/page_io.c@@ -339,6 +339,16 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc, goto out; } bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc); +#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) + if (page->mem_cgroup) { + struct cgroup_subsys_state *blkcg_css; + + blkcg_css = cgroup_get_e_css(page->mem_cgroup->css.cgroup, + &io_cgrp_subsys); + bio_associate_blkcg(bio, blkcg_css); + css_put(blkcg_css); + } +#endif
So, this ignores the cases where bdev_write_page() is the one which does the writes. If my reading is correct, only brd, zram, btt and pmem implement bdev_ops->rw_page() and take bdev_write_page() path, so it shouldn't be a problem in majority of cases. I don't think we need to address ->rw_page() case right now but it might be a good idea to add a comment explaining the ommission. Thanks. -- tejun