linux-kernel - [PATCH 4.13 065/110] gfs2: Fix debugfs glocks dump

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Message-Id: <20171003114243.940056653@linuxfoundation.org>
Date:   Tue,  3 Oct 2017 14:29:27 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andreas Gruenbacher <agruenba@...hat.com>,
        Bob Peterson <rpeterso@...hat.com>
Subject: [PATCH 4.13 065/110] gfs2: Fix debugfs glocks dump

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andreas Gruenbacher <agruenba@...hat.com>

commit 10201655b085df8e000822e496e5d4016a167a36 upstream.

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@...hat.com>
Signed-off-by: Bob Peterson <rpeterso@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/gfs2/glock.c |   14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1863,13 +1863,9 @@ static void *gfs2_glock_seq_start(struct
 {
 	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 {
@@ -1877,6 +1873,7 @@ static void *gfs2_glock_seq_start(struct
 	} while (gi->gl && n--);
 
 	gi->last_pos = *pos;
+
 	return gi->gl;
 }
 
@@ -1888,6 +1885,7 @@ static void *gfs2_glock_seq_next(struct
 	(*pos)++;
 	gi->last_pos = *pos;
 	gfs2_glock_iter_next(gi);
+
 	return gi->gl;
 }
 
@@ -1897,6 +1895,7 @@ static void gfs2_glock_seq_stop(struct s
 
 	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)
@@ -1959,12 +1958,10 @@ static int __gfs2_glocks_open(struct ino
 		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;
 }
@@ -1980,7 +1977,6 @@ static int gfs2_glocks_release(struct in
 	struct gfs2_glock_iter *gi = seq->private;
 
 	gi->gl = NULL;
-	rhashtable_walk_exit(&gi->hti);
 	return seq_release_private(inode, file);
 }