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Subject[PATCH 06/12] blkcg: associate a blkg for pages being evicted by swap
Date
From: "Dennis Zhou (Facebook)" <dennisszhou@gmail.com>

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 <dennisszhou@gmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
---
block/bio.c | 83 ++++++++++++++++++++++++++++++++-------------
include/linux/bio.h | 11 ++++--
mm/page_io.c | 2 +-
3 files changed, 68 insertions(+), 28 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 1d28d7ad2342..897c8ed9e572 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1957,30 +1957,6 @@ 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
@@ -2031,6 +2007,65 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
return 0;
}

+static int __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);
+
+ rcu_read_unlock();
+
+ return bio_associate_blkg(bio, blkg);
+}
+
+/**
+ * bio_associate_blkg_from_css - associate a bio with a specified css
+ * @bio: target bio
+ * @css: target css
+ *
+ * Associate @bio with the blkg found by combining the css's blkg and the
+ * request_queue of the @bio. This takes a reference on the css that will
+ * be put upon freeing of @bio.
+ */
+int bio_associate_blkg_from_css(struct bio *bio,
+ struct cgroup_subsys_state *css)
+{
+ css_get(css);
+ bio->bi_css = css;
+ return __bio_associate_blkg_from_css(bio, css);
+}
+EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
+
+#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.
+ *
+ * Note: this must be called after bio has an associated device.
+ */
+int bio_associate_blkg_from_page(struct bio *bio, struct page *page)
+{
+ struct cgroup_subsys_state *css;
+
+ if (unlikely(bio->bi_css))
+ return -EBUSY;
+ if (!page->mem_cgroup)
+ return 0;
+ css = cgroup_get_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
+ bio->bi_css = css;
+
+ return __bio_associate_blkg_from_css(bio, css);
+}
+#endif /* CONFIG_MEMCG */
+
/**
* bio_associate_create_blkg - associate a bio with a blkg from q
* @q: request_queue where bio is going
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 829cd0bb407d..c73a870ebc0e 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -533,21 +533,26 @@ 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);
+int 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 int bio_associate_blkg_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);
+int bio_associate_blkg_from_css(struct bio *bio,
+ struct cgroup_subsys_state *css);
int bio_associate_create_blkg(struct request_queue *q, struct bio *bio);
void bio_disassociate_task(struct bio *bio);
void bio_clone_blkcg_association(struct bio *dst, struct bio *src);
#else /* CONFIG_BLK_CGROUP */
static inline int bio_associate_blkcg(struct bio *bio,
struct cgroup_subsys_state *blkcg_css) { return 0; }
+static inline int bio_associate_blkg_from_css(struct bio *bio,
+ struct cgroup_subsys_state *css)
+{ return 0; }
static inline int bio_associate_create_blkg(struct request_queue *q,
struct bio *bio) { return 0; }
static inline void bio_disassociate_task(struct bio *bio) { }
diff --git a/mm/page_io.c b/mm/page_io.c
index aafd19ec1db4..573d3663d846 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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