From: Yu Kuai <yukuai3@xxxxxxxxxx>
After commit 35fe6d763229 ("block: use standard blktrace API to output
cgroup info for debug notes"), the field 'bfqg->blkg_path' is not used
and hence can be removed, and therefor blkg_path() is not used anymore
and can be removed.
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/bfq-cgroup.c | 51 ---------------------------------------------
block/bfq-iosched.h | 3 ---
block/blk-cgroup.h | 13 ------------
3 files changed, 67 deletions(-)
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index d442ee358fc2..b758693697c0 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -797,57 +797,6 @@ void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
*/
bfq_link_bfqg(bfqd, bfqg);
__bfq_bic_change_cgroup(bfqd, bic, bfqg);
- /*
- * Update blkg_path for bfq_log_* functions. We cache this
- * path, and update it here, for the following
- * reasons. Operations on blkg objects in blk-cgroup are
- * protected with the request_queue lock, and not with the
- * lock that protects the instances of this scheduler
- * (bfqd->lock). This exposes BFQ to the following sort of
- * race.
- *
- * The blkg_lookup performed in bfq_get_queue, protected
- * through rcu, may happen to return the address of a copy of
- * the original blkg. If this is the case, then the
- * bfqg_and_blkg_get performed in bfq_get_queue, to pin down
- * the blkg, is useless: it does not prevent blk-cgroup code
- * from destroying both the original blkg and all objects
- * directly or indirectly referred by the copy of the
- * blkg.
- *
- * On the bright side, destroy operations on a blkg invoke, as
- * a first step, hooks of the scheduler associated with the
- * blkg. And these hooks are executed with bfqd->lock held for
- * BFQ. As a consequence, for any blkg associated with the
- * request queue this instance of the scheduler is attached
- * to, we are guaranteed that such a blkg is not destroyed, and
- * that all the pointers it contains are consistent, while we
- * are holding bfqd->lock. A blkg_lookup performed with
- * bfqd->lock held then returns a fully consistent blkg, which
- * remains consistent until this lock is held.
- *
- * Thanks to the last fact, and to the fact that: (1) bfqg has
- * been obtained through a blkg_lookup in the above
- * assignment, and (2) bfqd->lock is being held, here we can
- * safely use the policy data for the involved blkg (i.e., the
- * field bfqg->pd) to get to the blkg associated with bfqg,
- * and then we can safely use any field of blkg. After we
- * release bfqd->lock, even just getting blkg through this
- * bfqg may cause dangling references to be traversed, as
- * bfqg->pd may not exist any more.
- *
- * In view of the above facts, here we cache, in the bfqg, any
- * blkg data we may need for this bic, and for its associated
- * bfq_queue. As of now, we need to cache only the path of the
- * blkg, which is used in the bfq_log_* functions.
- *
- * Finally, note that bfqg itself needs to be protected from
- * destruction on the blkg_free of the original blkg (which
- * invokes bfq_pd_free). We use an additional private
- * refcounter for bfqg, to let it disappear only after no
- * bfq_queue refers to it any longer.
- */
- blkg_path(bfqg_to_blkg(bfqg), bfqg->blkg_path, sizeof(bfqg->blkg_path));
bic->blkcg_serial_nr = serial_nr;
}
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 467e8cfc41a2..08ddf2cfae5b 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -1003,9 +1003,6 @@ struct bfq_group {
/* must be the first member */
struct blkg_policy_data pd;
- /* cached path for this blkg (see comments in bfq_bic_update_cgroup) */
- char blkg_path[128];
-
/* reference counter (see comments in bfq_bic_update_cgroup) */
refcount_t ref;
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 25833221a12b..6dcaf63c560a 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -301,19 +301,6 @@ static inline struct blkcg *cpd_to_blkcg(struct blkcg_policy_data *cpd)
return cpd ? cpd->blkcg : NULL;
}
-/**
- * blkg_path - format cgroup path of blkg
- * @blkg: blkg of interest
- * @buf: target buffer
- * @buflen: target buffer length
- *
- * Format the path of the cgroup of @blkg into @buf.
- */
-static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
-{
- return cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
-}
-
/**
* blkg_get - get a blkg reference
* @blkg: blkg to get
--
2.39.2
