[Cluster-devel] [RFC v2 PATCH 5/5] gfs2: add tracepoint debugging for gfs2_end_log_read

[Abhi Das <adas@redhat.com>]

Use a tracepoint and a counter in gfs2_jdesc to count the number of
outstanding reads (in pages) as we read through a journal to aid
debugging.

Signed-off-by: Abhi Das <adas@redhat.com>
---
 fs/gfs2/incore.h     |  1 +
 fs/gfs2/lops.c       |  3 +++
 fs/gfs2/ops_fstype.c |  1 +
 fs/gfs2/trace_gfs2.h | 25 +++++++++++++++++++++++++
 4 files changed, 30 insertions(+)

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 31188c0..bb4446d 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -512,6 +512,7 @@ struct gfs2_jdesc {
 
 	struct gfs2_log_header_host jd_jhead;
 	struct bio *jd_rd_bio; /* bio used for reading this journal */
+	atomic_t jd_rd_pg_ct;
 	unsigned int jd_found_blocks;
 	unsigned int jd_found_revokes;
 	unsigned int jd_replayed_blocks;
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 518b786..a261398 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -250,6 +250,7 @@ static void gfs2_end_log_read(struct bio *bio, int error)
 		ptr = page_address(page);
 		error = gfs2_log_header_in(&lh, ptr);
 		last = page_private(page);
+		atomic_dec(&jd->jd_rd_pg_ct);
 
 		if (!test_bit(JDF_JHEAD, &jd->jd_flags)) {
 			mempool_free(page, gfs2_page_pool);
@@ -273,6 +274,7 @@ static void gfs2_end_log_read(struct bio *bio, int error)
 	}
 
 	bio_put(bio);
+	trace_gfs2_end_log_read(jd);
 }
 
 /**
@@ -454,6 +456,7 @@ void gfs2_log_read_extent(struct gfs2_jdesc *jd, u64 dblock,
 			ret = bio_add_page(bio, page, sb->s_blocksize, 0);
 			WARN_ON(ret == 0);
 		}
+		atomic_inc(&jd->jd_rd_pg_ct);
 		bio->bi_private = jd;
 	}
 }
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index 4a17eaf..ac9855a 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -643,6 +643,7 @@ static int gfs2_jindex_hold(struct gfs2_sbd *sdp, struct gfs2_holder *ji_gh)
 			break;
 		}
 		jd->jd_rd_bio = NULL;
+		atomic_set(&jd->jd_rd_pg_ct, 0);
 
 		spin_lock(&sdp->sd_jindex_spin);
 		jd->jd_jid = sdp->sd_journals++;
diff --git a/fs/gfs2/trace_gfs2.h b/fs/gfs2/trace_gfs2.h
index d1de2ed..9f0cc8d 100644
--- a/fs/gfs2/trace_gfs2.h
+++ b/fs/gfs2/trace_gfs2.h
@@ -613,6 +613,31 @@ TRACE_EVENT(gfs2_rs,
 		  rs_func_name(__entry->func), (unsigned long)__entry->free)
 );
 
+TRACE_EVENT(gfs2_end_log_read,
+
+	TP_PROTO(const struct gfs2_jdesc *jd),
+
+
+	TP_ARGS(jd),
+
+	TP_STRUCT__entry(
+		__field(        dev_t,        dev               )
+		__field(	unsigned int, jid		)
+		__field(	unsigned int, pages 	        )
+	),
+
+	TP_fast_assign(
+		__entry->dev            = jd->jd_inode->i_sb->s_dev;
+		__entry->jid		= jd->jd_jid;
+		__entry->pages		= atomic_read(&jd->jd_rd_pg_ct);
+	),
+
+	TP_printk("%u,%u end_log_read jid:%u outstanding pages:%u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  (unsigned int)__entry->jid,
+		  (unsigned int)__entry->pages)
+);
+
 #endif /* _TRACE_GFS2_H */
 
 /* This part must be outside protection */
-- 
2.4.11