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Subject[PATCH 07/13] blkcg: associate a blkg for pages being evicted by swap
Date
A prior patch in this series added blkg association to bios issued by
cgroups. There are two other paths that we want to attribute work back
to the appropriate cgroup: swap and writeback. Here we modify the way
swap tags bios to include the blkg. Writeback will be tackle in the next
patch.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
---
block/bio.c | 62 +++++++++++++++++++++++++++------------------
include/linux/bio.h | 6 ++---
mm/page_io.c | 2 +-
3 files changed, 42 insertions(+), 28 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index efca5ae607a4..4600808ac606 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1958,30 +1958,6 @@ 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
@@ -2059,6 +2035,44 @@ static void __bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
bio->bi_blkg = blkg_try_get_closest(blkg);
}

+static void __bio_associate_blkg_from_css(struct bio *bio,
+ struct cgroup_subsys_state *css)
+{
+ struct blkcg_gq *blkg;
+
+ rcu_read_lock();
+
+ blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_disk->queue);
+ __bio_associate_blkg(bio, blkg);
+
+ rcu_read_unlock();
+}
+
+#ifdef CONFIG_MEMCG
+/**
+ * bio_associate_blkg_from_page - associate a bio with the page's blkg
+ * @bio: target bio
+ * @page: the page to lookup the blkcg from
+ *
+ * Associate @bio with the blkg from @page's owning memcg and the respective
+ * request_queue. This works like every other associate function wrt
+ * references.
+ */
+void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
+{
+ struct cgroup_subsys_state *css;
+
+ if (unlikely(bio->bi_css))
+ return;
+ if (!bio_has_queue(bio) || !page->mem_cgroup)
+ return;
+
+ css = cgroup_get_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
+ bio->bi_css = css;
+ __bio_associate_blkg_from_css(bio, css);
+}
+#endif /* CONFIG_MEMCG */
+
/**
* bio_associate_blkg - associate a bio with a blkg from q
* @bio: target bio
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 8bc9d9b29fd3..ad322232db3e 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -510,10 +510,10 @@ do { \
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);
+void bio_associate_blkg_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; }
+static inline void bio_associate_blkg_from_page(struct bio *bio,
+ struct page *page) { }
#endif

#ifdef CONFIG_BLK_CGROUP
diff --git a/mm/page_io.c b/mm/page_io.c
index 257fdd67308d..409dcd438488 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -339,7 +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);
+ bio_associate_blkg_from_page(bio, page);
count_swpout_vm_event(page);
set_page_writeback(page);
unlock_page(page);
--
2.17.1
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