[Cluster-devel] [PATCH 3/3] gfs2: Glock dump improvement (2)

[Andreas Gruenbacher]

In gfs2_glock_iter_next, use rhashtable_walk_curr to stay at the current
hash table entry instead of scanning the hash table from the start for
each entry that wraps across a buffer boundary.

With this change, there is no benefit in allocating a bigger seq file
buffer anymore (if there even was one before).

Signed-off-by: Andreas Gruenbacher <agruenba at redhat.com>
---
 fs/gfs2/glock.c | 56 ++++++++++++++++++++++++++++++++------------------------
 1 file changed, 32 insertions(+), 24 deletions(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 93c7cd2325b4..ca4cb052f0c3 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1924,20 +1924,36 @@ void gfs2_glock_exit(void)
 	destroy_workqueue(gfs2_delete_workqueue);
 }
 
-static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi)
+static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi, loff_t n)
 {
-	while ((gi->gl = rhashtable_walk_next(&gi->hti))) {
-		if (IS_ERR(gi->gl)) {
-			if (PTR_ERR(gi->gl) == -EAGAIN)
-				continue;
-			gi->gl = NULL;
-			return;
+	bool curr = false;
+
+	if (n == 0) {
+		curr = true;
+		n = 1;
+	}
+
+	do {
+		if (curr) {
+			gi->gl = rhashtable_walk_curr(&gi->hti);
+			curr = false;
+		} else
+			gi->gl = rhashtable_walk_next(&gi->hti);
+		if (IS_ERR_OR_NULL(gi->gl)) {
+			if (!gi->gl)
+				return;
+			if (PTR_ERR(gi->gl) != -EAGAIN) {
+				gi->gl = NULL;
+				return;
+			}
+			n = 1;
+			continue;
 		}
 		/* Skip entries for other sb and dead entries */
-		if (gi->sdp == gi->gl->gl_name.ln_sbd &&
-		    !__lockref_is_dead(&gi->gl->gl_lockref))
-			return;
-	}
+		if (gi->sdp != gi->gl->gl_name.ln_sbd ||
+		    __lockref_is_dead(&gi->gl->gl_lockref))
+			continue;
+	} while (--n);
 }
 
 static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
@@ -1947,10 +1963,10 @@ static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
 	loff_t n;
 
 	/*
-	 * From the current position, we can either skip to the next hash table
-	 * entry or start from the beginning.
+	 * We can either stay where we are, skip to the next hash table
+	 * entry, or start from the beginning.
 	 */
-	if (*pos <= gi->last_pos) {
+	if (*pos < gi->last_pos) {
 		rhashtable_walk_exit(&gi->hti);
 		rhashtable_walk_enter(&gl_hash_table, &gi->hti);
 		n = *pos + 1;
@@ -1960,12 +1976,7 @@ static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
 	if (rhashtable_walk_start(&gi->hti) != 0)
 		return NULL;
 
-	while (n--) {
-		gfs2_glock_iter_next(gi);
-		if (!gi->gl)
-			break;
-	}
-
+	gfs2_glock_iter_next(gi, n);
 	gi->last_pos = *pos;
 	return gi->gl;
 }
@@ -1977,7 +1988,7 @@ static void *gfs2_glock_seq_next(struct seq_file *seq, void *iter_ptr,
 
 	(*pos)++;
 	gi->last_pos = *pos;
-	gfs2_glock_iter_next(gi);
+	gfs2_glock_iter_next(gi, 1);
 	return gi->gl;
 }
 
@@ -2055,9 +2066,6 @@ static int __gfs2_glocks_open(struct inode *inode, struct file *file,
 		 * first call to rhashtable_walk_next gets us the first entry.
 		 */
 		gi->last_pos = -1;
-		seq->buf = kmalloc(GFS2_SEQ_GOODSIZE, GFP_KERNEL | __GFP_NOWARN);
-		if (seq->buf)
-			seq->size = GFS2_SEQ_GOODSIZE;
 		gi->gl = NULL;
 		rhashtable_walk_enter(&gl_hash_table, &gi->hti);
 	}
-- 
2.14.3