blkcg: associate a blkg for pages being evicted by swap

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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index 80c948d..387480d 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -1956,30 +1956,6 @@ 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
@@ -2030,6 +2006,65 @@ 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 829cd0b..c73a870 100644 (file)
--- 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 aafd19e..573d366 100644 (file)
--- 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);