Sorry for the late noise, but now when there are no stats, the name has
still been printed out without adding a new line, which doesn't seem to
be inline with the documented 'nested keyed' file format.
in particular, I'm now seeing this line with 2 keys:
253:10 253:5 rbytes=0 wbytes=0 rios=0 wios=1 dbytes=0 dios=0
^~~~~~ ^~~~~
I'm not sure if a separate temporary buffer would make more sense or
switching back to seq_get_buf?
Figuring out `has_stats` first doesn't seem to be trivial due to the
`pd_stat_fn` calls.
Or of course, just include the newlines unconditionally?
Unless seq_file has/gets another way to roll back the buffer?
On Tue, Aug 10, 2021 at 05:26:23PM +0200, Christoph Hellwig wrote:
> seq_get_buf is a crutch that undoes all the memory safety of the
> seq_file interface. Use the normal seq_printf interfaces instead.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> block/blk-cgroup.c | 30 ++++++------------------------
> block/blk-iocost.c | 23 +++++++++--------------
> block/blk-iolatency.c | 38 +++++++++++++++++++-------------------
> block/mq-deadline-cgroup.c | 8 +++-----
> include/linux/blk-cgroup.h | 4 ++--
> 5 files changed, 39 insertions(+), 64 deletions(-)
>
> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> index 52aa0540ccaf..b8ec47dcce42 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -877,8 +877,6 @@ static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
> bool has_stats = false;
> const char *dname;
> unsigned seq;
> - char *buf;
> - size_t size = seq_get_buf(s, &buf), off = 0;
> int i;
>
> if (!blkg->online)
> @@ -888,13 +886,7 @@ static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
> if (!dname)
> return;
>
> - /*
> - * Hooray string manipulation, count is the size written NOT
> - * INCLUDING THE \0, so size is now count+1 less than what we
> - * had before, but we want to start writing the next bit from
> - * the \0 so we only add count to buf.
> - */
> - off += scnprintf(buf+off, size-off, "%s ", dname);
> + seq_printf(s, "%s ", dname);
>
> do {
> seq = u64_stats_fetch_begin(&bis->sync);
> @@ -909,40 +901,30 @@ static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
>
> if (rbytes || wbytes || rios || wios) {
> has_stats = true;
> - off += scnprintf(buf+off, size-off,
> - "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
> + seq_printf(s, "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
> rbytes, wbytes, rios, wios,
> dbytes, dios);
> }
>
> if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
> has_stats = true;
> - off += scnprintf(buf+off, size-off, " use_delay=%d delay_nsec=%llu",
> + seq_printf(s, " use_delay=%d delay_nsec=%llu",
> atomic_read(&blkg->use_delay),
> atomic64_read(&blkg->delay_nsec));
> }
>
> for (i = 0; i < BLKCG_MAX_POLS; i++) {
> struct blkcg_policy *pol = blkcg_policy[i];
> - size_t written;
>
> if (!blkg->pd[i] || !pol->pd_stat_fn)
> continue;
>
> - written = pol->pd_stat_fn(blkg->pd[i], buf+off, size-off);
> - if (written)
> + if (pol->pd_stat_fn(blkg->pd[i], s))
> has_stats = true;
> - off += written;
> }
>
> - if (has_stats) {
> - if (off < size - 1) {
> - off += scnprintf(buf+off, size-off, "\n");
> - seq_commit(s, off);
> - } else {
> - seq_commit(s, -1);
> - }
> - }
> + if (has_stats)
> + seq_printf(s, "\n");
> }
>
> static int blkcg_print_stat(struct seq_file *sf, void *v)
> diff --git a/block/blk-iocost.c b/block/blk-iocost.c
> index 5fac3757e6e0..89b21a360b2c 100644
> --- a/block/blk-iocost.c
> +++ b/block/blk-iocost.c
> @@ -2988,34 +2988,29 @@ static void ioc_pd_free(struct blkg_policy_data *pd)
> kfree(iocg);
> }
>
> -static size_t ioc_pd_stat(struct blkg_policy_data *pd, char *buf, size_t size)
> +static bool ioc_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
> {
> struct ioc_gq *iocg = pd_to_iocg(pd);
> struct ioc *ioc = iocg->ioc;
> - size_t pos = 0;
>
> if (!ioc->enabled)
> - return 0;
> + return false;
>
> if (iocg->level == 0) {
> unsigned vp10k = DIV64_U64_ROUND_CLOSEST(
> ioc->vtime_base_rate * 10000,
> VTIME_PER_USEC);
> - pos += scnprintf(buf + pos, size - pos, " cost.vrate=%u.%02u",
> - vp10k / 100, vp10k % 100);
> + seq_printf(s, " cost.vrate=%u.%02u", vp10k / 100, vp10k % 100);
> }
>
> - pos += scnprintf(buf + pos, size - pos, " cost.usage=%llu",
> - iocg->last_stat.usage_us);
> + seq_printf(s, " cost.usage=%llu", iocg->last_stat.usage_us);
>
> if (blkcg_debug_stats)
> - pos += scnprintf(buf + pos, size - pos,
> - " cost.wait=%llu cost.indebt=%llu cost.indelay=%llu",
> - iocg->last_stat.wait_us,
> - iocg->last_stat.indebt_us,
> - iocg->last_stat.indelay_us);
> -
> - return pos;
> + seq_printf(s, " cost.wait=%llu cost.indebt=%llu cost.indelay=%llu",
> + iocg->last_stat.wait_us,
> + iocg->last_stat.indebt_us,
> + iocg->last_stat.indelay_us);
> + return true;
> }
>
> static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
> diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
> index d8b0d8bd132b..c0545f9da549 100644
> --- a/block/blk-iolatency.c
> +++ b/block/blk-iolatency.c
> @@ -890,8 +890,7 @@ static int iolatency_print_limit(struct seq_file *sf, void *v)
> return 0;
> }
>
> -static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf,
> - size_t size)
> +static bool iolatency_ssd_stat(struct iolatency_grp *iolat, struct seq_file *s)
> {
> struct latency_stat stat;
> int cpu;
> @@ -906,39 +905,40 @@ static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf,
> preempt_enable();
>
> if (iolat->rq_depth.max_depth == UINT_MAX)
> - return scnprintf(buf, size, " missed=%llu total=%llu depth=max",
> - (unsigned long long)stat.ps.missed,
> - (unsigned long long)stat.ps.total);
> - return scnprintf(buf, size, " missed=%llu total=%llu depth=%u",
> - (unsigned long long)stat.ps.missed,
> - (unsigned long long)stat.ps.total,
> - iolat->rq_depth.max_depth);
> + seq_printf(s, " missed=%llu total=%llu depth=max",
> + (unsigned long long)stat.ps.missed,
> + (unsigned long long)stat.ps.total);
> + else
> + seq_printf(s, " missed=%llu total=%llu depth=%u",
> + (unsigned long long)stat.ps.missed,
> + (unsigned long long)stat.ps.total,
> + iolat->rq_depth.max_depth);
> + return true;
> }
>
> -static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf,
> - size_t size)
> +static bool iolatency_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
> {
> struct iolatency_grp *iolat = pd_to_lat(pd);
> unsigned long long avg_lat;
> unsigned long long cur_win;
>
> if (!blkcg_debug_stats)
> - return 0;
> + return false;
>
> if (iolat->ssd)
> - return iolatency_ssd_stat(iolat, buf, size);
> + return iolatency_ssd_stat(iolat, s);
>
> avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC);
> cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC);
> if (iolat->rq_depth.max_depth == UINT_MAX)
> - return scnprintf(buf, size, " depth=max avg_lat=%llu win=%llu",
> - avg_lat, cur_win);
> -
> - return scnprintf(buf, size, " depth=%u avg_lat=%llu win=%llu",
> - iolat->rq_depth.max_depth, avg_lat, cur_win);
> + seq_printf(s, " depth=max avg_lat=%llu win=%llu",
> + avg_lat, cur_win);
> + else
> + seq_printf(s, " depth=%u avg_lat=%llu win=%llu",
> + iolat->rq_depth.max_depth, avg_lat, cur_win);
> + return true;
> }
>
> -
> static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp,
> struct request_queue *q,
> struct blkcg *blkcg)
> diff --git a/block/mq-deadline-cgroup.c b/block/mq-deadline-cgroup.c
> index 3b4bfddec39f..b48a4b962f90 100644
> --- a/block/mq-deadline-cgroup.c
> +++ b/block/mq-deadline-cgroup.c
> @@ -52,7 +52,7 @@ struct dd_blkcg *dd_blkcg_from_bio(struct bio *bio)
> return dd_blkcg_from_pd(pd);
> }
>
> -static size_t dd_pd_stat(struct blkg_policy_data *pd, char *buf, size_t size)
> +static bool dd_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
> {
> static const char *const prio_class_name[] = {
> [IOPRIO_CLASS_NONE] = "NONE",
> @@ -61,12 +61,10 @@ static size_t dd_pd_stat(struct blkg_policy_data *pd, char *buf, size_t size)
> [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",
> + seq_printf(s, " [%s] dispatched=%u inserted=%u merged=%u",
> prio_class_name[prio],
> ddcg_sum(blkcg, dispatched, prio) +
> ddcg_sum(blkcg, merged, prio) -
> @@ -75,7 +73,7 @@ static size_t dd_pd_stat(struct blkg_policy_data *pd, char *buf, size_t size)
> ddcg_sum(blkcg, completed, prio),
> ddcg_sum(blkcg, merged, prio));
>
> - return res;
> + return true;
> }
>
> static struct blkg_policy_data *dd_pd_alloc(gfp_t gfp, struct request_queue *q,
> diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
> index 37048438872c..b4de2010fba5 100644
> --- a/include/linux/blk-cgroup.h
> +++ b/include/linux/blk-cgroup.h
> @@ -152,8 +152,8 @@ typedef void (blkcg_pol_online_pd_fn)(struct blkg_policy_data *pd);
> typedef void (blkcg_pol_offline_pd_fn)(struct blkg_policy_data *pd);
> typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data *pd);
> typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkg_policy_data *pd);
> -typedef size_t (blkcg_pol_stat_pd_fn)(struct blkg_policy_data *pd, char *buf,
> - size_t size);
> +typedef bool (blkcg_pol_stat_pd_fn)(struct blkg_policy_data *pd,
> + struct seq_file *s);
>
> struct blkcg_policy {
> int plid;
> --
> 2.30.2
>
>
