Revert "block/mq-deadline: Add cgroup support"
authorTejun Heo <tj@kernel.org>
Wed, 11 Aug 2021 17:41:45 +0000 (07:41 -1000)
committerJens Axboe <axboe@kernel.dk>
Wed, 11 Aug 2021 19:47:26 +0000 (13:47 -0600)
This reverts commit 08a9ad8bf607 ("block/mq-deadline: Add cgroup support")
and a follow-up commit c06bc5a3fb42 ("block/mq-deadline: Remove a
WARN_ON_ONCE() call"). The added cgroup support has the following issues:

* It breaks cgroup interface file format rule by adding custom elements to a
  nested key-value file.

* It registers mq-deadline as a cgroup-aware policy even though all it's
  doing is collecting per-cgroup stats. Even if we need these stats, this
  isn't the right way to add them.

* It hasn't been reviewed from cgroup side.

Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block/Kconfig.iosched
block/Makefile
block/mq-deadline-cgroup.c [deleted file]
block/mq-deadline-cgroup.h [deleted file]
block/mq-deadline.c [moved from block/mq-deadline-main.c with 95% similarity]

index 64053d6..2f2158e 100644 (file)
@@ -9,12 +9,6 @@ config MQ_IOSCHED_DEADLINE
        help
          MQ version of the deadline IO scheduler.
 
-config MQ_IOSCHED_DEADLINE_CGROUP
-       tristate
-       default y
-       depends on MQ_IOSCHED_DEADLINE
-       depends on BLK_CGROUP
-
 config MQ_IOSCHED_KYBER
        tristate "Kyber I/O scheduler"
        default y
index bfbe4e1..1e1afa1 100644 (file)
@@ -22,8 +22,6 @@ obj-$(CONFIG_BLK_CGROUP_IOPRIO)       += blk-ioprio.o
 obj-$(CONFIG_BLK_CGROUP_IOLATENCY)     += blk-iolatency.o
 obj-$(CONFIG_BLK_CGROUP_IOCOST)        += blk-iocost.o
 obj-$(CONFIG_MQ_IOSCHED_DEADLINE)      += mq-deadline.o
-mq-deadline-y += mq-deadline-main.o
-mq-deadline-$(CONFIG_MQ_IOSCHED_DEADLINE_CGROUP)+= mq-deadline-cgroup.o
 obj-$(CONFIG_MQ_IOSCHED_KYBER) += kyber-iosched.o
 bfq-y                          := bfq-iosched.o bfq-wf2q.o bfq-cgroup.o
 obj-$(CONFIG_IOSCHED_BFQ)      += bfq.o
diff --git a/block/mq-deadline-cgroup.c b/block/mq-deadline-cgroup.c
deleted file mode 100644 (file)
index 3b4bfdd..0000000
+++ /dev/null
@@ -1,126 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-#include <linux/blk-cgroup.h>
-#include <linux/ioprio.h>
-
-#include "mq-deadline-cgroup.h"
-
-static struct blkcg_policy dd_blkcg_policy;
-
-static struct blkcg_policy_data *dd_cpd_alloc(gfp_t gfp)
-{
-       struct dd_blkcg *pd;
-
-       pd = kzalloc(sizeof(*pd), gfp);
-       if (!pd)
-               return NULL;
-       pd->stats = alloc_percpu_gfp(typeof(*pd->stats),
-                                    GFP_KERNEL | __GFP_ZERO);
-       if (!pd->stats) {
-               kfree(pd);
-               return NULL;
-       }
-       return &pd->cpd;
-}
-
-static void dd_cpd_free(struct blkcg_policy_data *cpd)
-{
-       struct dd_blkcg *dd_blkcg = container_of(cpd, typeof(*dd_blkcg), cpd);
-
-       free_percpu(dd_blkcg->stats);
-       kfree(dd_blkcg);
-}
-
-static struct dd_blkcg *dd_blkcg_from_pd(struct blkg_policy_data *pd)
-{
-       return container_of(blkcg_to_cpd(pd->blkg->blkcg, &dd_blkcg_policy),
-                           struct dd_blkcg, cpd);
-}
-
-/*
- * Convert an association between a block cgroup and a request queue into a
- * pointer to the mq-deadline information associated with a (blkcg, queue) pair.
- */
-struct dd_blkcg *dd_blkcg_from_bio(struct bio *bio)
-{
-       struct blkg_policy_data *pd;
-
-       pd = blkg_to_pd(bio->bi_blkg, &dd_blkcg_policy);
-       if (!pd)
-               return NULL;
-
-       return dd_blkcg_from_pd(pd);
-}
-
-static size_t dd_pd_stat(struct blkg_policy_data *pd, char *buf, size_t size)
-{
-       static const char *const prio_class_name[] = {
-               [IOPRIO_CLASS_NONE]     = "NONE",
-               [IOPRIO_CLASS_RT]       = "RT",
-               [IOPRIO_CLASS_BE]       = "BE",
-               [IOPRIO_CLASS_IDLE]     = "IDLE",
-       };
-       struct dd_blkcg *blkcg = dd_blkcg_from_pd(pd);
-       int res = 0;
-       u8 prio;
-
-       for (prio = 0; prio < ARRAY_SIZE(blkcg->stats->stats); prio++)
-               res += scnprintf(buf + res, size - res,
-                       " [%s] dispatched=%u inserted=%u merged=%u",
-                       prio_class_name[prio],
-                       ddcg_sum(blkcg, dispatched, prio) +
-                       ddcg_sum(blkcg, merged, prio) -
-                       ddcg_sum(blkcg, completed, prio),
-                       ddcg_sum(blkcg, inserted, prio) -
-                       ddcg_sum(blkcg, completed, prio),
-                       ddcg_sum(blkcg, merged, prio));
-
-       return res;
-}
-
-static struct blkg_policy_data *dd_pd_alloc(gfp_t gfp, struct request_queue *q,
-                                           struct blkcg *blkcg)
-{
-       struct dd_blkg *pd;
-
-       pd = kzalloc(sizeof(*pd), gfp);
-       if (!pd)
-               return NULL;
-       return &pd->pd;
-}
-
-static void dd_pd_free(struct blkg_policy_data *pd)
-{
-       struct dd_blkg *dd_blkg = container_of(pd, typeof(*dd_blkg), pd);
-
-       kfree(dd_blkg);
-}
-
-static struct blkcg_policy dd_blkcg_policy = {
-       .cpd_alloc_fn           = dd_cpd_alloc,
-       .cpd_free_fn            = dd_cpd_free,
-
-       .pd_alloc_fn            = dd_pd_alloc,
-       .pd_free_fn             = dd_pd_free,
-       .pd_stat_fn             = dd_pd_stat,
-};
-
-int dd_activate_policy(struct request_queue *q)
-{
-       return blkcg_activate_policy(q, &dd_blkcg_policy);
-}
-
-void dd_deactivate_policy(struct request_queue *q)
-{
-       blkcg_deactivate_policy(q, &dd_blkcg_policy);
-}
-
-int __init dd_blkcg_init(void)
-{
-       return blkcg_policy_register(&dd_blkcg_policy);
-}
-
-void __exit dd_blkcg_exit(void)
-{
-       blkcg_policy_unregister(&dd_blkcg_policy);
-}
diff --git a/block/mq-deadline-cgroup.h b/block/mq-deadline-cgroup.h
deleted file mode 100644 (file)
index 0143fd7..0000000
+++ /dev/null
@@ -1,114 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-
-#if !defined(_MQ_DEADLINE_CGROUP_H_)
-#define _MQ_DEADLINE_CGROUP_H_
-
-#include <linux/blk-cgroup.h>
-
-struct request_queue;
-
-/**
- * struct io_stats_per_prio - I/O statistics per I/O priority class.
- * @inserted: Number of inserted requests.
- * @merged: Number of merged requests.
- * @dispatched: Number of dispatched requests.
- * @completed: Number of I/O completions.
- */
-struct io_stats_per_prio {
-       local_t inserted;
-       local_t merged;
-       local_t dispatched;
-       local_t completed;
-};
-
-/* I/O statistics per I/O cgroup per I/O priority class (IOPRIO_CLASS_*). */
-struct blkcg_io_stats {
-       struct io_stats_per_prio stats[4];
-};
-
-/**
- * struct dd_blkcg - Per cgroup data.
- * @cpd: blkcg_policy_data structure.
- * @stats: I/O statistics.
- */
-struct dd_blkcg {
-       struct blkcg_policy_data cpd;   /* must be the first member */
-       struct blkcg_io_stats __percpu *stats;
-};
-
-/*
- * Count one event of type 'event_type' and with I/O priority class
- * 'prio_class'.
- */
-#define ddcg_count(ddcg, event_type, prio_class) do {                  \
-if (ddcg) {                                                            \
-       struct blkcg_io_stats *io_stats = get_cpu_ptr((ddcg)->stats);   \
-                                                                       \
-       BUILD_BUG_ON(!__same_type((ddcg), struct dd_blkcg *));          \
-       BUILD_BUG_ON(!__same_type((prio_class), u8));                   \
-       local_inc(&io_stats->stats[(prio_class)].event_type);           \
-       put_cpu_ptr(io_stats);                                          \
-}                                                                      \
-} while (0)
-
-/*
- * Returns the total number of ddcg_count(ddcg, event_type, prio_class) calls
- * across all CPUs. No locking or barriers since it is fine if the returned
- * sum is slightly outdated.
- */
-#define ddcg_sum(ddcg, event_type, prio) ({                            \
-       unsigned int cpu;                                               \
-       u32 sum = 0;                                                    \
-                                                                       \
-       BUILD_BUG_ON(!__same_type((ddcg), struct dd_blkcg *));          \
-       BUILD_BUG_ON(!__same_type((prio), u8));                         \
-       for_each_present_cpu(cpu)                                       \
-               sum += local_read(&per_cpu_ptr((ddcg)->stats, cpu)->    \
-                                 stats[(prio)].event_type);            \
-       sum;                                                            \
-})
-
-#ifdef CONFIG_BLK_CGROUP
-
-/**
- * struct dd_blkg - Per (cgroup, request queue) data.
- * @pd: blkg_policy_data structure.
- */
-struct dd_blkg {
-       struct blkg_policy_data pd;     /* must be the first member */
-};
-
-struct dd_blkcg *dd_blkcg_from_bio(struct bio *bio);
-int dd_activate_policy(struct request_queue *q);
-void dd_deactivate_policy(struct request_queue *q);
-int __init dd_blkcg_init(void);
-void __exit dd_blkcg_exit(void);
-
-#else /* CONFIG_BLK_CGROUP */
-
-static inline struct dd_blkcg *dd_blkcg_from_bio(struct bio *bio)
-{
-       return NULL;
-}
-
-static inline int dd_activate_policy(struct request_queue *q)
-{
-       return 0;
-}
-
-static inline void dd_deactivate_policy(struct request_queue *q)
-{
-}
-
-static inline int dd_blkcg_init(void)
-{
-       return 0;
-}
-
-static inline void dd_blkcg_exit(void)
-{
-}
-
-#endif /* CONFIG_BLK_CGROUP */
-
-#endif /* _MQ_DEADLINE_CGROUP_H_ */
similarity index 95%
rename from block/mq-deadline-main.c
rename to block/mq-deadline.c
index 6f612e6..a09761c 100644 (file)
@@ -25,7 +25,6 @@
 #include "blk-mq-debugfs.h"
 #include "blk-mq-tag.h"
 #include "blk-mq-sched.h"
-#include "mq-deadline-cgroup.h"
 
 /*
  * See Documentation/block/deadline-iosched.rst
@@ -57,6 +56,14 @@ enum dd_prio {
 
 enum { DD_PRIO_COUNT = 3 };
 
+/* I/O statistics per I/O priority. */
+struct io_stats_per_prio {
+       local_t inserted;
+       local_t merged;
+       local_t dispatched;
+       local_t completed;
+};
+
 /* I/O statistics for all I/O priorities (enum dd_prio). */
 struct io_stats {
        struct io_stats_per_prio stats[DD_PRIO_COUNT];
@@ -79,9 +86,6 @@ struct deadline_data {
         * run time data
         */
 
-       /* Request queue that owns this data structure. */
-       struct request_queue *queue;
-
        struct dd_per_prio per_prio[DD_PRIO_COUNT];
 
        /* Data direction of latest dispatched request. */
@@ -234,10 +238,8 @@ static void dd_merged_requests(struct request_queue *q, struct request *req,
        struct deadline_data *dd = q->elevator->elevator_data;
        const u8 ioprio_class = dd_rq_ioclass(next);
        const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
-       struct dd_blkcg *blkcg = next->elv.priv[0];
 
        dd_count(dd, merged, prio);
-       ddcg_count(blkcg, merged, ioprio_class);
 
        /*
         * if next expires before rq, assign its expire time to rq
@@ -375,7 +377,6 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd,
 {
        struct request *rq, *next_rq;
        enum dd_data_dir data_dir;
-       struct dd_blkcg *blkcg;
        enum dd_prio prio;
        u8 ioprio_class;
 
@@ -474,8 +475,6 @@ done:
        ioprio_class = dd_rq_ioclass(rq);
        prio = ioprio_class_to_prio[ioprio_class];
        dd_count(dd, dispatched, prio);
-       blkcg = rq->elv.priv[0];
-       ddcg_count(blkcg, dispatched, ioprio_class);
        /*
         * If the request needs its target zone locked, do it.
         */
@@ -569,8 +568,6 @@ static void dd_exit_sched(struct elevator_queue *e)
        struct deadline_data *dd = e->elevator_data;
        enum dd_prio prio;
 
-       dd_deactivate_policy(dd->queue);
-
        for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
                struct dd_per_prio *per_prio = &dd->per_prio[prio];
 
@@ -584,7 +581,7 @@ static void dd_exit_sched(struct elevator_queue *e)
 }
 
 /*
- * Initialize elevator private data (deadline_data) and associate with blkcg.
+ * initialize elevator private data (deadline_data).
  */
 static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
 {
@@ -593,12 +590,6 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
        enum dd_prio prio;
        int ret = -ENOMEM;
 
-       /*
-        * Initialization would be very tricky if the queue is not frozen,
-        * hence the warning statement below.
-        */
-       WARN_ON_ONCE(!percpu_ref_is_zero(&q->q_usage_counter));
-
        eq = elevator_alloc(q, e);
        if (!eq)
                return ret;
@@ -614,8 +605,6 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
        if (!dd->stats)
                goto free_dd;
 
-       dd->queue = q;
-
        for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
                struct dd_per_prio *per_prio = &dd->per_prio[prio];
 
@@ -635,17 +624,9 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
        spin_lock_init(&dd->lock);
        spin_lock_init(&dd->zone_lock);
 
-       ret = dd_activate_policy(q);
-       if (ret)
-               goto free_stats;
-
-       ret = 0;
        q->elevator = eq;
        return 0;
 
-free_stats:
-       free_percpu(dd->stats);
-
 free_dd:
        kfree(dd);
 
@@ -718,7 +699,6 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
        u8 ioprio_class = IOPRIO_PRIO_CLASS(ioprio);
        struct dd_per_prio *per_prio;
        enum dd_prio prio;
-       struct dd_blkcg *blkcg;
        LIST_HEAD(free);
 
        lockdep_assert_held(&dd->lock);
@@ -729,18 +709,8 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
         */
        blk_req_zone_write_unlock(rq);
 
-       /*
-        * If a block cgroup has been associated with the submitter and if an
-        * I/O priority has been set in the associated block cgroup, use the
-        * lowest of the cgroup priority and the request priority for the
-        * request. If no priority has been set in the request, use the cgroup
-        * priority.
-        */
        prio = ioprio_class_to_prio[ioprio_class];
        dd_count(dd, inserted, prio);
-       blkcg = dd_blkcg_from_bio(rq->bio);
-       ddcg_count(blkcg, inserted, ioprio_class);
-       rq->elv.priv[0] = blkcg;
 
        if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
                blk_mq_free_requests(&free);
@@ -789,10 +759,12 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
        spin_unlock(&dd->lock);
 }
 
-/* Callback from inside blk_mq_rq_ctx_init(). */
+/*
+ * Nothing to do here. This is defined only to ensure that .finish_request
+ * method is called upon request completion.
+ */
 static void dd_prepare_request(struct request *rq)
 {
-       rq->elv.priv[0] = NULL;
 }
 
 /*
@@ -815,13 +787,11 @@ static void dd_finish_request(struct request *rq)
 {
        struct request_queue *q = rq->q;
        struct deadline_data *dd = q->elevator->elevator_data;
-       struct dd_blkcg *blkcg = rq->elv.priv[0];
        const u8 ioprio_class = dd_rq_ioclass(rq);
        const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
        struct dd_per_prio *per_prio = &dd->per_prio[prio];
 
        dd_count(dd, completed, prio);
-       ddcg_count(blkcg, completed, ioprio_class);
 
        if (blk_queue_is_zoned(q)) {
                unsigned long flags;
@@ -1144,26 +1114,11 @@ MODULE_ALIAS("mq-deadline-iosched");
 
 static int __init deadline_init(void)
 {
-       int ret;
-
-       ret = elv_register(&mq_deadline);
-       if (ret)
-               goto out;
-       ret = dd_blkcg_init();
-       if (ret)
-               goto unreg;
-
-out:
-       return ret;
-
-unreg:
-       elv_unregister(&mq_deadline);
-       goto out;
+       return elv_register(&mq_deadline);
 }
 
 static void __exit deadline_exit(void)
 {
-       dd_blkcg_exit();
        elv_unregister(&mq_deadline);
 }