FAILED: patch "[PATCH] gfs2: Fix debugfs glocks dump" failed to apply to 4.9-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 10201655b085df8e000822e496e5d4016a167a36 Mon Sep 17 00:00:00 2001
From: Andreas Gruenbacher <agruenba@redhat.com>
Date: Tue, 19 Sep 2017 07:15:35 -0500
Subject: [PATCH] gfs2: Fix debugfs glocks dump

The switch to rhashtables (commit 88ffbf3e03) broke the debugfs glock
dump (/sys/kernel/debug/gfs2/<device>/glocks) for dumps bigger than a
single buffer: the right function for restarting an rhashtable iteration
from the beginning of the hash table is rhashtable_walk_enter;
rhashtable_walk_stop + rhashtable_walk_start will just resume from the
current position.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Cc: stable@vger.kernel.org # v4.3+

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 98e845b7841b..11066d8647d2 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1945,13 +1945,9 @@ static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
 {
 	struct gfs2_glock_iter *gi = seq->private;
 	loff_t n = *pos;
-	int ret;
-
-	if (gi->last_pos <= *pos)
-		n = (*pos - gi->last_pos);
 
-	ret = rhashtable_walk_start(&gi->hti);
-	if (ret)
+	rhashtable_walk_enter(&gl_hash_table, &gi->hti);
+	if (rhashtable_walk_start(&gi->hti) != 0)
 		return NULL;
 
 	do {
@@ -1959,6 +1955,7 @@ static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
 	} while (gi->gl && n--);
 
 	gi->last_pos = *pos;
+
 	return gi->gl;
 }
 
@@ -1970,6 +1967,7 @@ static void *gfs2_glock_seq_next(struct seq_file *seq, void *iter_ptr,
 	(*pos)++;
 	gi->last_pos = *pos;
 	gfs2_glock_iter_next(gi);
+
 	return gi->gl;
 }
 
@@ -1980,6 +1978,7 @@ static void gfs2_glock_seq_stop(struct seq_file *seq, void *iter_ptr)
 
 	gi->gl = NULL;
 	rhashtable_walk_stop(&gi->hti);
+	rhashtable_walk_exit(&gi->hti);
 }
 
 static int gfs2_glock_seq_show(struct seq_file *seq, void *iter_ptr)
@@ -2042,12 +2041,10 @@ static int __gfs2_glocks_open(struct inode *inode, struct file *file,
 		struct gfs2_glock_iter *gi = seq->private;
 
 		gi->sdp = inode->i_private;
-		gi->last_pos = 0;
 		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);
 	}
 	return ret;
 }
@@ -2063,7 +2060,6 @@ static int gfs2_glocks_release(struct inode *inode, struct file *file)
 	struct gfs2_glock_iter *gi = seq->private;
 
 	gi->gl = NULL;
-	rhashtable_walk_exit(&gi->hti);
 	return seq_release_private(inode, file);
 }