blk-cgroup: stop using seq_get_buf

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@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210810152623.1796144-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 52aa054..b8ec47d 100644 (file)
--- 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 5fac375..89b21a3 100644 (file)
--- 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 81be009..4c06faf 100644 (file)
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -886,8 +886,7 @@ 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;
@@ -902,39 +901,40 @@ 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 3b4bfdd..b48a4b9 100644 (file)
--- 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 3704843..b4de201 100644 (file)
--- 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;