[RFC PATCH 3/5] block: untangle ioprio from BLK_CGROUP and BLK_DEV_THROTTLING

Jason B. Akers
2014-10-29T18:36:31Z

From: Dan Williams <dan.j.williams@intel.com>

If BLK_CGROUP is disabled, still enable ionice to set advice on bios.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason B. Akers <jason.b.akers@intel.com>
---
block/bio.c | 43 +++++++++++---------------------
block/blk.h | 2 ++
include/linux/bio.h | 68 +++++++++++++++++++++++++++++++++++++++++++++++----
3 files changed, 79 insertions(+), 34 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index e133b5c..b93ae04 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1980,7 +1980,6 @@ struct bio_set *bioset_create_nobvec(unsigned int pool_size, unsigned int front_
}
EXPORT_SYMBOL(bioset_create_nobvec);

-#ifdef CONFIG_BLK_CGROUP
/**
* bio_associate_current - associate a bio with %current
* @bio: target bio
@@ -1989,34 +1988,28 @@ EXPORT_SYMBOL(bioset_create_nobvec);
* layer will treat @bio as if it were issued by %current no matter which
* task actually issues it.
*
- * This function takes an extra reference of @task's io_context and blkcg
- * which will be put when @bio is released. The caller must own @bio,
- * ensure %current->io_context exists, and is responsible for synchronizing
- * calls to this function.
+ * When BLK_CGROUP=y this function takes an extra reference of @task's
+ * io_context and blkcg which will be put when @bio is released. The caller
+ * must own @bio, ensure %current->io_context exists, and is responsible for
+ * synchronizing calls to this function.
+ *
+ * When BLK_CGROUP=n this function simply sets the bio priority and cache advice
*/
int bio_associate_current(struct bio *bio)
{
struct io_context *ioc;
- struct cgroup_subsys_state *css;
-
- if (bio->bi_ioc)
- return -EBUSY;
+ int rc;

ioc = current->io_context;
if (!ioc)
return -ENOENT;

- /* acquire active ref on @ioc and associate */
- get_io_context_active(ioc);
- bio->bi_ioc = ioc;
- bio_set_prio(bio, ioprio_best(ioc->ioprio, bio_prio(bio)));
+ rc = bio_associate_ioc(bio, ioc);
+ if (rc)
+ return rc;

- /* associate blkcg if exists */
- rcu_read_lock();
- css = task_css(current, blkio_cgrp_id);
- if (css && css_tryget_online(css))
- bio->bi_css = css;
- rcu_read_unlock();
+ bio_associate_blkcg(bio, current);
+ bio_set_prio(bio, ioprio_best(ioc->ioprio, bio_prio(bio)));

return 0;
}
@@ -2027,18 +2020,10 @@ int bio_associate_current(struct bio *bio)
*/
void bio_disassociate_task(struct bio *bio)
{
- if (bio->bi_ioc) {
- put_io_context(bio->bi_ioc);
- bio->bi_ioc = NULL;
- }
- if (bio->bi_css) {
- css_put(bio->bi_css);
- bio->bi_css = NULL;
- }
+ bio_disassociate_ioc(bio);
+ bio_disassociate_blkcg(bio);
}

-#endif /* CONFIG_BLK_CGROUP */
-
static void __init biovec_init_slabs(void)
{
int i;
diff --git a/block/blk.h b/block/blk.h
index 43b0361..6d7c4df 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -274,6 +274,8 @@ extern void blk_throtl_exit(struct request_queue *q);
#else /* CONFIG_BLK_DEV_THROTTLING */
static inline bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
{
+ /* set prio, but don't throttle */
+ bio_associate_current(bio);
return false;
}
static inline void blk_throtl_drain(struct request_queue *q) { }
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 7347f48..8419319 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -22,6 +22,7 @@

#include <linux/highmem.h>
#include <linux/mempool.h>
+#include <linux/cgroup.h>
#include <linux/ioprio.h>
#include <linux/bug.h>

@@ -469,13 +470,70 @@ extern struct bio_vec *bvec_alloc(gfp_t, int, unsigned long *, mempool_t *);
extern void bvec_free(mempool_t *, struct bio_vec *, unsigned int);
extern unsigned int bvec_nr_vecs(unsigned short idx);

-#ifdef CONFIG_BLK_CGROUP
int bio_associate_current(struct bio *bio);
void bio_disassociate_task(struct bio *bio);
-#else /* CONFIG_BLK_CGROUP */
-static inline int bio_associate_current(struct bio *bio) { return -ENOENT; }
-static inline void bio_disassociate_task(struct bio *bio) { }
-#endif /* CONFIG_BLK_CGROUP */
+
+#ifdef CONFIG_BLK_CGROUP
+static inline int bio_associate_ioc(struct bio *bio, struct io_context *ioc)
+{
+ if (bio->bi_ioc)
+ return -EBUSY;
+
+ /* acquire active ref on @ioc and associate */
+ get_io_context_active(ioc);
+ bio->bi_ioc = ioc;
+
+ return 0;
+}
+
+static inline void bio_associate_blkcg(struct bio *bio,
+ struct task_struct *task)
+{
+ struct cgroup_subsys_state *css;
+
+ /* associate blkcg if exists */
+ rcu_read_lock();
+ css = task_css(task, blkio_cgrp_id);
+ if (css && css_tryget(css))
+ bio->bi_css = css;
+ rcu_read_unlock();
+}
+
+static inline void bio_disassociate_ioc(struct bio *bio)
+{
+ if (bio->bi_ioc) {
+ put_io_context(bio->bi_ioc);
+ bio->bi_ioc = NULL;
+ }
+}
+
+static inline void bio_disassociate_blkcg(struct bio *bio)
+{
+ if (bio->bi_css) {
+ css_put(bio->bi_css);
+ bio->bi_css = NULL;
+ }
+}
+#else
+static inline int bio_associate_ioc(struct bio *bio, struct io_context *ioc)
+{
+ return 0;
+}
+
+static inline void bio_associate_blkcg(struct bio *bio,
+ struct task_struct *task)
+{
+}
+
+static inline void bio_disassociate_ioc(struct bio *bio)
+{
+}
+
+static inline void bio_disassociate_blkcg(struct bio *bio)
+{
+}
+
+#endif

#ifdef CONFIG_HIGHMEM
/*