blkcg: Track DISCARD statistics and output them in cgroup io.stat

Add tracking of REQ_OP_DISCARD ios to the per-cgroup io.stat.  Two
fields, dbytes and dios, to respectively count the total bytes and
number of discards are added.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andy Newell <newella@fb.com>
Cc: Michael Callahan <michaelcallahan@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 9 insertions, 4 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 7e2c19ce1a08..1942357d7165 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -567,6 +567,7 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
                 [BLKG_RWSTAT_WRITE]     = "Write",
                 [BLKG_RWSTAT_SYNC]      = "Sync",
                 [BLKG_RWSTAT_ASYNC]     = "Async",
+                [BLKG_RWSTAT_DISCARD]   = "Discard",
         };
         const char *dname = blkg_dev_name(pd->blkg);
         u64 v;
@@ -580,7 +581,8 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
                            (unsigned long long)atomic64_read(&rwstat->aux_cnt[i]));
 
         v = atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_READ]) +
-                atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_WRITE]);
+                atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_WRITE]) +
+                atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_DISCARD]);
         seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
         return v;
 }
@@ -959,7 +961,7 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
                 const char *dname;
                 char *buf;
                 struct blkg_rwstat rwstat;
-                u64 rbytes, wbytes, rios, wios;
+                u64 rbytes, wbytes, rios, wios, dbytes, dios;
                 size_t size = seq_get_buf(sf, &buf), off = 0;
                 int i;
                 bool has_stats = false;
@@ -982,19 +984,22 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
                                         offsetof(struct blkcg_gq, stat_bytes));
                 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));
                 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]);
 
                 spin_unlock_irq(blkg->q->queue_lock);
 
                 if (rbytes || wbytes || rios || wios) {
                         has_stats = true;
                         off += scnprintf(buf+off, size-off,
-                                         "rbytes=%llu wbytes=%llu rios=%llu wios=%llu",
-                                         rbytes, wbytes, rios, wios);
+                                         "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
+                                         rbytes, wbytes, rios, wios,
+                                         dbytes, dios);
                 }
 
                 if (!blkcg_debug_stats)