Skip to content

Commit

Permalink
blkcg: implement blkg_[rw]stat_recursive_sum() and blkg_[rw]stat_merge()
Browse files Browse the repository at this point in the history 
Implement blkg_[rw]stat_recursive_sum() and blkg_[rw]stat_merge().
The former two collect the [rw]stats designated by the target policy
data and offset from the pd's subtree.  The latter two add one
[rw]stat to another.

Note that the recursive sum functions require the queue lock to be
held on entry to make blkg online test reliable.  This is necessary to
properly handle stats of a dying blkg.

These will be used to implement hierarchical stats.

Signed-off-by: Tejun Heo <[email protected]>
Acked-by: Vivek Goyal <[email protected]>
  • Loading branch information
@htejun
htejun committed Jan 9, 2013
1 parent b50da39 commit 16b3de6
Show file tree
Hide file tree
Showing 2 changed files with 142 additions and 0 deletions.
107 changes: 107 additions & 0 deletions block/blk-cgroup.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,26 @@ EXPORT_SYMBOL_GPL(blkcg_root);

static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];

static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
struct request_queue *q, bool update_hint);

/**
* blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
* @d_blkg: loop cursor pointing to the current descendant
* @pos_cgrp: used for iteration
* @p_blkg: target blkg to walk descendants of
*
* Walk @c_blkg through the descendants of @p_blkg. Must be used with RCU
* read locked. If called under either blkcg or queue lock, the iteration
* is guaranteed to include all and only online blkgs. The caller may
* update @pos_cgrp by calling cgroup_rightmost_descendant() to skip
* subtree.
*/
#define blkg_for_each_descendant_pre(d_blkg, pos_cgrp, p_blkg) \
cgroup_for_each_descendant_pre((pos_cgrp), (p_blkg)->blkcg->css.cgroup) \
if (((d_blkg) = __blkg_lookup(cgroup_to_blkcg(pos_cgrp), \
(p_blkg)->q, false)))

static bool blkcg_policy_enabled(struct request_queue *q,
const struct blkcg_policy *pol)
{
Expand Down Expand Up @@ -127,6 +147,17 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
return NULL;
}

/**
* __blkg_lookup - internal version of blkg_lookup()
* @blkcg: blkcg of interest
* @q: request_queue of interest
* @update_hint: whether to update lookup hint with the result or not
*
* This is internal version and shouldn't be used by policy
* implementations. Looks up blkgs for the @blkcg - @q pair regardless of
* @q's bypass state. If @update_hint is %true, the caller should be
* holding @q->queue_lock and lookup hint is updated on success.
*/
static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
struct request_queue *q, bool update_hint)
{
Expand Down Expand Up @@ -585,6 +616,82 @@ u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
}
EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);

/**
* blkg_stat_recursive_sum - collect hierarchical blkg_stat
* @pd: policy private data of interest
* @off: offset to the blkg_stat in @pd
*
* Collect the blkg_stat specified by @off from @pd and all its online
* descendants and return the sum. The caller must be holding the queue
* lock for online tests.
*/
u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off)
{
struct blkcg_policy *pol = blkcg_policy[pd->plid];
struct blkcg_gq *pos_blkg;
struct cgroup *pos_cgrp;
u64 sum;

lockdep_assert_held(pd->blkg->q->queue_lock);

sum = blkg_stat_read((void *)pd + off);

rcu_read_lock();
blkg_for_each_descendant_pre(pos_blkg, pos_cgrp, pd_to_blkg(pd)) {
struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
struct blkg_stat *stat = (void *)pos_pd + off;

if (pos_blkg->online)
sum += blkg_stat_read(stat);
}
rcu_read_unlock();

return sum;
}
EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);

/**
* blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
* @pd: policy private data of interest
* @off: offset to the blkg_stat in @pd
*
* Collect the blkg_rwstat specified by @off from @pd and all its online
* descendants and return the sum. The caller must be holding the queue
* lock for online tests.
*/
struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
int off)
{
struct blkcg_policy *pol = blkcg_policy[pd->plid];
struct blkcg_gq *pos_blkg;
struct cgroup *pos_cgrp;
struct blkg_rwstat sum;
int i;

lockdep_assert_held(pd->blkg->q->queue_lock);

sum = blkg_rwstat_read((void *)pd + off);

rcu_read_lock();
blkg_for_each_descendant_pre(pos_blkg, pos_cgrp, pd_to_blkg(pd)) {
struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
struct blkg_rwstat *rwstat = (void *)pos_pd + off;
struct blkg_rwstat tmp;

if (!pos_blkg->online)
continue;

tmp = blkg_rwstat_read(rwstat);

for (i = 0; i < BLKG_RWSTAT_NR; i++)
sum.cnt[i] += tmp.cnt[i];
}
rcu_read_unlock();

return sum;
}
EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);

/**
* blkg_conf_prep - parse and prepare for per-blkg config update
* @blkcg: target block cgroup
Expand Down
35 changes: 35 additions & 0 deletions block/blk-cgroup.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -164,6 +164,10 @@ u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off);
u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
int off);

u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off);
struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
int off);

struct blkg_conf_ctx {
struct gendisk *disk;
struct blkcg_gq *blkg;
Expand Down Expand Up @@ -413,6 +417,18 @@ static inline void blkg_stat_reset(struct blkg_stat *stat)
stat->cnt = 0;
}

/**
* blkg_stat_merge - merge a blkg_stat into another
* @to: the destination blkg_stat
* @from: the source
*
* Add @from's count to @to.
*/
static inline void blkg_stat_merge(struct blkg_stat *to, struct blkg_stat *from)
{
blkg_stat_add(to, blkg_stat_read(from));
}

/**
* blkg_rwstat_add - add a value to a blkg_rwstat
* @rwstat: target blkg_rwstat
Expand Down Expand Up @@ -484,6 +500,25 @@ static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
}

/**
* blkg_rwstat_merge - merge a blkg_rwstat into another
* @to: the destination blkg_rwstat
* @from: the source
*
* Add @from's counts to @to.
*/
static inline void blkg_rwstat_merge(struct blkg_rwstat *to,
struct blkg_rwstat *from)
{
struct blkg_rwstat v = blkg_rwstat_read(from);
int i;

u64_stats_update_begin(&to->syncp);
for (i = 0; i < BLKG_RWSTAT_NR; i++)
to->cnt[i] += v.cnt[i];
u64_stats_update_end(&to->syncp);
}

#else /* CONFIG_BLK_CGROUP */

struct cgroup;
Expand Down

0 comments on commit 16b3de6

Please sign in to comment.