linux-kernel - [PATCH 4.9 013/108] gfs2: Use rhashtable walk interface in glock_hash

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Message-Id: <20170615175337.795849258@linuxfoundation.org>
Date:   Thu, 15 Jun 2017 19:52:19 +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, Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 013/108] gfs2: Use rhashtable walk interface in glock_hash_walk

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

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

From: Herbert Xu <herbert@...dor.apana.org.au>


[ Upstream commit 6a25478077d987edc5e2f880590a2bc5fcab4441 ]

The function glock_hash_walk walks the rhashtable by hand.  This
is broken because if it catches the hash table in the middle of
a rehash, then it will miss entries.

This patch replaces the manual walk by using the rhashtable walk
interface.

Fixes: 88ffbf3e037e ("GFS2: Use resizable hash table for glocks")
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/gfs2/glock.c |   30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1425,26 +1425,32 @@ static struct shrinker glock_shrinker =
  * @sdp: the filesystem
  * @bucket: the bucket
  *
+ * Note that the function can be called multiple times on the same
+ * object.  So the user must ensure that the function can cope with
+ * that.
  */
 
 static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
 {
 	struct gfs2_glock *gl;
-	struct rhash_head *pos;
-	const struct bucket_table *tbl;
-	int i;
-
-	rcu_read_lock();
-	tbl = rht_dereference_rcu(gl_hash_table.tbl, &gl_hash_table);
-	for (i = 0; i < tbl->size; i++) {
-		rht_for_each_entry_rcu(gl, pos, tbl, i, gl_node) {
+	struct rhashtable_iter iter;
+
+	rhashtable_walk_enter(&gl_hash_table, &iter);
+
+	do {
+		gl = ERR_PTR(rhashtable_walk_start(&iter));
+		if (gl)
+			continue;
+
+		while ((gl = rhashtable_walk_next(&iter)) && !IS_ERR(gl))
 			if ((gl->gl_name.ln_sbd == sdp) &&
 			    lockref_get_not_dead(&gl->gl_lockref))
 				examiner(gl);
-		}
-	}
-	rcu_read_unlock();
-	cond_resched();
+
+		rhashtable_walk_stop(&iter);
+	} while (cond_resched(), gl == ERR_PTR(-EAGAIN));
+
+	rhashtable_walk_exit(&iter);
 }
 
 /**