[PATCH v4 2/2] f2fs: add iostat latency statistics support for discard

[Yangtao Li]

In this patch, it adds to account discard latency. This allows us to
track the discard io latency of the system lightweightly after enabling
iostat.

Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
---
v4:
-split it to two patch
 fs/f2fs/f2fs.h              |  1 +
 fs/f2fs/iostat.c            |  6 ++++--
 fs/f2fs/segment.c           |  8 +++++++-
 include/trace/events/f2fs.h | 12 ++++++++++--
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 3d883201e7a5..1779f3596176 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1112,6 +1112,7 @@ enum page_type {
 	META_FLUSH,
 	IPU,		/* the below types are used by tracepoints only. */
 	OPU,
+	DISCARD,	/* used by iostat */
 };
 
 enum temp_type {
diff --git a/fs/f2fs/iostat.c b/fs/f2fs/iostat.c
index 5d496d5b70d3..f40b8915ae1b 100644
--- a/fs/f2fs/iostat.c
+++ b/fs/f2fs/iostat.c
@@ -235,7 +235,7 @@ void iostat_update_and_unbind_ctx(struct bio *bio)
 {
 	struct bio_iostat_ctx *iostat_ctx = bio->bi_private;
 
-	if (op_is_write(bio_op(bio)))
+	if (op_is_write(bio_op(bio)) && !op_is_discard(bio_op(bio)))
 		bio->bi_private = iostat_ctx->sbi;
 	else
 		bio->bi_private = iostat_ctx->iostat_private;
@@ -251,7 +251,9 @@ void iostat_update_submit_ctx(struct bio *bio, enum page_type type)
 
 	iostat_ctx->submit_ts = jiffies;
 
-	if (op_is_write(bio_op(bio))) {
+	if (type == DISCARD) {
+		lat_type = DISCARD_LAT;
+	} else if (op_is_write(bio_op(bio))) {
 		lat_type = bio->bi_opf & REQ_SYNC ?
 				WRITE_SYNC_DATA_LAT : WRITE_ASYNC_DATA_LAT;
 		lat_type = (enum iostat_lat_type)(lat_type + type);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index fc0734e4fb92..be24e9c945a3 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1100,9 +1100,12 @@ static void __remove_discard_cmd(struct f2fs_sb_info *sbi,
 
 static void f2fs_submit_discard_endio(struct bio *bio)
 {
-	struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
+	struct discard_cmd *dc;
 	unsigned long flags;
 
+	iostat_update_and_unbind_ctx(bio);
+	dc = bio->bi_private;
+
 	spin_lock_irqsave(&dc->lock, flags);
 	if (!dc->error)
 		dc->error = blk_status_to_errno(bio->bi_status);
@@ -1276,6 +1279,9 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
 		bio->bi_private = dc;
 		bio->bi_end_io = f2fs_submit_discard_endio;
 		bio->bi_opf |= flag;
+
+		iostat_alloc_and_bind_ctx(sbi, bio, dc);
+		iostat_update_submit_ctx(bio, DISCARD);
 		submit_bio(bio);
 
 		atomic_inc(&dcc->issued_discard);
diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
index 040a430e1199..385291ac9ad5 100644
--- a/include/trace/events/f2fs.h
+++ b/include/trace/events/f2fs.h
@@ -2078,6 +2078,9 @@ TRACE_EVENT(f2fs_iostat_latency,
 		__field(unsigned int,	m_wr_as_peak)
 		__field(unsigned int,	m_wr_as_avg)
 		__field(unsigned int,	m_wr_as_cnt)
+		__field(unsigned int,	discard_peak)
+		__field(unsigned int,	discard_avg)
+		__field(unsigned int,	discard_cnt)
 	),
 
 	TP_fast_assign(
@@ -2109,6 +2112,9 @@ TRACE_EVENT(f2fs_iostat_latency,
 		__entry->m_wr_as_peak	= iostat_lat[WRITE_ASYNC_META_LAT].peak_lat;
 		__entry->m_wr_as_avg	= iostat_lat[WRITE_ASYNC_META_LAT].avg_lat;
 		__entry->m_wr_as_cnt	= iostat_lat[WRITE_ASYNC_META_LAT].cnt;
+		__entry->discard_peak	= iostat_lat[DISCARD_LAT].peak_lat;
+		__entry->discard_avg	= iostat_lat[DISCARD_LAT].avg_lat;
+		__entry->discard_cnt	= iostat_lat[DISCARD_LAT].cnt;
 	),
 
 	TP_printk("dev = (%d,%d), "
@@ -2116,7 +2122,8 @@ TRACE_EVENT(f2fs_iostat_latency,
 		"rd_data [%u/%u/%u], rd_node [%u/%u/%u], rd_meta [%u/%u/%u], "
 		"wr_sync_data [%u/%u/%u], wr_sync_node [%u/%u/%u], "
 		"wr_sync_meta [%u/%u/%u], wr_async_data [%u/%u/%u], "
-		"wr_async_node [%u/%u/%u], wr_async_meta [%u/%u/%u]",
+		"wr_async_node [%u/%u/%u], wr_async_meta [%u/%u/%u], "
+		"discard [%u/%u/%u]",
 		show_dev(__entry->dev),
 		__entry->d_rd_peak, __entry->d_rd_avg, __entry->d_rd_cnt,
 		__entry->n_rd_peak, __entry->n_rd_avg, __entry->n_rd_cnt,
@@ -2126,7 +2133,8 @@ TRACE_EVENT(f2fs_iostat_latency,
 		__entry->m_wr_s_peak, __entry->m_wr_s_avg, __entry->m_wr_s_cnt,
 		__entry->d_wr_as_peak, __entry->d_wr_as_avg, __entry->d_wr_as_cnt,
 		__entry->n_wr_as_peak, __entry->n_wr_as_avg, __entry->n_wr_as_cnt,
-		__entry->m_wr_as_peak, __entry->m_wr_as_avg, __entry->m_wr_as_cnt)
+		__entry->m_wr_as_peak, __entry->m_wr_as_avg, __entry->m_wr_as_cnt,
+		__entry->discard_peak, __entry->discard_avg, __entry->discard_cnt)
 );
 #endif
 
-- 
2.35.1