swap,blkcg: issue swap io with the appropriate context
For backcharging we need to know who the page belongs to when swapping
it out. We don't worry about things that do ->rw_page (zram etc) at the
moment, we're only worried about pages that actually go to a block
device.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/bio.c b/block/bio.c
index 0445715..5f84f5c 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -2015,6 +2015,30 @@ EXPORT_SYMBOL(bioset_init_from_src);
#ifdef CONFIG_BLK_CGROUP
+#ifdef CONFIG_MEMCG
+/**
+ * bio_associate_blkcg_from_page - associate a bio with the page's blkcg
+ * @bio: target bio
+ * @page: the page to lookup the blkcg from
+ *
+ * Associate @bio with the blkcg from @page's owning memcg. This works like
+ * every other associate function wrt references.
+ */
+int bio_associate_blkcg_from_page(struct bio *bio, struct page *page)
+{
+ struct cgroup_subsys_state *blkcg_css;
+
+ if (unlikely(bio->bi_css))
+ return -EBUSY;
+ if (!page->mem_cgroup)
+ return 0;
+ blkcg_css = cgroup_get_e_css(page->mem_cgroup->css.cgroup,
+ &io_cgrp_subsys);
+ bio->bi_css = blkcg_css;
+ return 0;
+}
+#endif /* CONFIG_MEMCG */
+
/**
* bio_associate_blkcg - associate a bio with the specified blkcg
* @bio: target bio