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blk-cgroup: pass blkg_rwstat structures by reference
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Returning a structure generates rather bad code, so switch to passing
by reference.  Also don't require the structure to be zeroed and add
to the 0-initialized counters, but actually set the counters to the
calculated value.

Acked-by: Tejun Heo <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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Christoph Hellwig authored and axboe committed Jun 20, 2019
1 parent 239eeb0 commit 5d0b6e4
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Showing 3 changed files with 32 additions and 28 deletions.
15 changes: 9 additions & 6 deletions block/bfq-cgroup.c
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Original file line number Diff line number Diff line change
Expand Up @@ -935,9 +935,9 @@ static u64 bfqg_prfill_stat_recursive(struct seq_file *sf,
static u64 bfqg_prfill_rwstat_recursive(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat sum = blkg_rwstat_recursive_sum(pd_to_blkg(pd),
&blkcg_policy_bfq,
off);
struct blkg_rwstat sum;

blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq, off, &sum);
return __blkg_prfill_rwstat(sf, pd, &sum);
}

Expand Down Expand Up @@ -975,9 +975,12 @@ static int bfqg_print_stat_sectors(struct seq_file *sf, void *v)
static u64 bfqg_prfill_sectors_recursive(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat tmp = blkg_rwstat_recursive_sum(pd->blkg, NULL,
offsetof(struct blkcg_gq, stat_bytes));
u64 sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
struct blkg_rwstat tmp;
u64 sum;

blkg_rwstat_recursive_sum(pd->blkg, NULL,
offsetof(struct blkcg_gq, stat_bytes), &tmp);
sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);

return __blkg_prfill_u64(sf, pd, sum >> 9);
Expand Down
31 changes: 16 additions & 15 deletions block/blk-cgroup.c
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Original file line number Diff line number Diff line change
Expand Up @@ -597,17 +597,19 @@ EXPORT_SYMBOL_GPL(blkg_prfill_stat);
u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
struct blkg_rwstat rwstat = { };

blkg_rwstat_read((void *)pd + off, &rwstat);
return __blkg_prfill_rwstat(sf, pd, &rwstat);
}
EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);

static u64 blkg_prfill_rwstat_field(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd->blkg + off);
struct blkg_rwstat rwstat = { };

blkg_rwstat_read((void *)pd->blkg + off, &rwstat);
return __blkg_prfill_rwstat(sf, pd, &rwstat);
}

Expand Down Expand Up @@ -649,8 +651,9 @@ static u64 blkg_prfill_rwstat_field_recursive(struct seq_file *sf,
struct blkg_policy_data *pd,
int off)
{
struct blkg_rwstat rwstat = blkg_rwstat_recursive_sum(pd->blkg,
NULL, off);
struct blkg_rwstat rwstat;

blkg_rwstat_recursive_sum(pd->blkg, NULL, off, &rwstat);
return __blkg_prfill_rwstat(sf, pd, &rwstat);
}

Expand Down Expand Up @@ -731,6 +734,7 @@ EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
* @blkg: blkg of interest
* @pol: blkcg_policy which contains the blkg_rwstat
* @off: offset to the blkg_rwstat in blkg_policy_data or @blkg
* @sum: blkg_rwstat structure containing the results
*
* Collect the blkg_rwstat specified by @blkg, @pol and @off and all its
* online descendants and their aux counts. The caller must be holding the
Expand All @@ -739,12 +743,11 @@ EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
* If @pol is NULL, blkg_rwstat is at @off bytes into @blkg; otherwise, it
* is at @off bytes into @blkg's blkg_policy_data of the policy.
*/
struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
struct blkcg_policy *pol, int off)
void blkg_rwstat_recursive_sum(struct blkcg_gq *blkg, struct blkcg_policy *pol,
int off, struct blkg_rwstat *sum)
{
struct blkcg_gq *pos_blkg;
struct cgroup_subsys_state *pos_css;
struct blkg_rwstat sum = { };
unsigned int i;

lockdep_assert_held(&blkg->q->queue_lock);
Expand All @@ -762,12 +765,10 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
rwstat = (void *)pos_blkg + off;

for (i = 0; i < BLKG_RWSTAT_NR; i++)
atomic64_add(blkg_rwstat_read_counter(rwstat, i),
&sum.aux_cnt[i]);
atomic64_set(&sum->aux_cnt[i],
blkg_rwstat_read_counter(rwstat, i));
}
rcu_read_unlock();

return sum;
}
EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);

Expand Down Expand Up @@ -953,14 +954,14 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)

spin_lock_irq(&blkg->q->queue_lock);

rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
offsetof(struct blkcg_gq, stat_bytes));
blkg_rwstat_recursive_sum(blkg, NULL,
offsetof(struct blkcg_gq, stat_bytes), &rwstat);
rbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]);
wbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
dbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_DISCARD]);

rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
offsetof(struct blkcg_gq, stat_ios));
blkg_rwstat_recursive_sum(blkg, NULL,
offsetof(struct blkcg_gq, stat_ios), &rwstat);
rios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]);
wios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
dios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_DISCARD]);
Expand Down
14 changes: 7 additions & 7 deletions include/linux/blk-cgroup.h
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Original file line number Diff line number Diff line change
Expand Up @@ -224,8 +224,8 @@ int blkg_print_stat_ios_recursive(struct seq_file *sf, void *v);

u64 blkg_stat_recursive_sum(struct blkcg_gq *blkg,
struct blkcg_policy *pol, int off);
struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
struct blkcg_policy *pol, int off);
void blkg_rwstat_recursive_sum(struct blkcg_gq *blkg, struct blkcg_policy *pol,
int off, struct blkg_rwstat *sum);

struct blkg_conf_ctx {
struct gendisk *disk;
Expand Down Expand Up @@ -700,15 +700,14 @@ static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
*
* Read the current snapshot of @rwstat and return it in the aux counts.
*/
static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
static inline void blkg_rwstat_read(struct blkg_rwstat *rwstat,
struct blkg_rwstat *result)
{
struct blkg_rwstat result;
int i;

for (i = 0; i < BLKG_RWSTAT_NR; i++)
atomic64_set(&result.aux_cnt[i],
atomic64_set(&result->aux_cnt[i],
percpu_counter_sum_positive(&rwstat->cpu_cnt[i]));
return result;
}

/**
Expand All @@ -721,8 +720,9 @@ static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
*/
static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat)
{
struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);
struct blkg_rwstat tmp = { };

blkg_rwstat_read(rwstat, &tmp);
return atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
}
Expand Down

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