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Subject[PATCH 05/13] swap,blkcg: issue swap io with the appropriate context
Date
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 <jbacik@fb.com>
---
block/bio.c | 24 ++++++++++++++++++++++++
include/linux/bio.h | 7 +++++++
mm/page_io.c | 1 +
3 files changed, 32 insertions(+)

diff --git a/block/bio.c b/block/bio.c
index 57c4b1986e76..c77fe1b4caa8 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -2005,6 +2005,30 @@ EXPORT_SYMBOL(bioset_create);

#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
diff --git a/include/linux/bio.h b/include/linux/bio.h
index f2f3f1428e81..eef1e8877048 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -545,6 +545,13 @@ do { \
#define bio_dev(bio) \
disk_devt((bio)->bi_disk)

+#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
+int bio_associate_blkcg_from_page(struct bio *bio, struct page *page);
+#else
+static inline int bio_associate_blkcg_from_page(struct bio *bio,
+ struct page *page) { return 0; }
+#endif
+
#ifdef CONFIG_BLK_CGROUP
int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css);
int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg);
diff --git a/mm/page_io.c b/mm/page_io.c
index a552cb37e220..aafd19ec1db4 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -339,6 +339,7 @@ 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);
+ bio_associate_blkcg_from_page(bio, page);
count_swpout_vm_event(page);
set_page_writeback(page);
unlock_page(page);
--
2.14.3
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