netdev - [PATCH RFC 1/2] rhashtable: accept GFP flags in rhashtable_walk

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Message-Id: <1456708013-19590-1-git-send-email-me@bobcopeland.com>
Date:	Sun, 28 Feb 2016 20:06:52 -0500
From:	Bob Copeland <me@...copeland.com>
To:	linux-wireless@...r.kernel.org
Cc:	Johannes Berg <johannes@...solutions.net>,
	Bob Copeland <me@...copeland.com>, Thomas Graf <tgraf@...g.ch>,
	netdev@...r.kernel.org
Subject: [PATCH RFC 1/2] rhashtable: accept GFP flags in rhashtable_walk_init

In certain cases, the 802.11 mesh pathtable code wants to
iterate over all of the entries in the forwarding table from
the receive path, which is inside an RCU read-side critical
section.  Enable walks inside atomic sections by allowing
GFP_ATOMIC allocations for the walker state.

Change all existing callsites to pass in GFP_KERNEL.

Cc: Thomas Graf <tgraf@...g.ch>
Cc: netdev@...r.kernel.org
Signed-off-by: Bob Copeland <me@...copeland.com>
---
 include/linux/rhashtable.h | 3 ++-
 lib/rhashtable.c           | 6 ++++--
 net/ipv6/ila/ila_xlat.c    | 3 ++-
 net/netfilter/nft_hash.c   | 4 ++--
 net/netlink/af_netlink.c   | 3 ++-
 net/sctp/proc.c            | 3 ++-
 6 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 63bd7601b6de..3eef0802a0cd 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -346,7 +346,8 @@ struct bucket_table *rhashtable_insert_slow(struct rhashtable *ht,
 					    struct bucket_table *old_tbl);
 int rhashtable_insert_rehash(struct rhashtable *ht, struct bucket_table *tbl);
 
-int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter);
+int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter,
+			 gfp_t gfp);
 void rhashtable_walk_exit(struct rhashtable_iter *iter);
 int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
 void *rhashtable_walk_next(struct rhashtable_iter *iter);
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index cc808707d1cf..5d845ffd7982 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -487,6 +487,7 @@ EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
  * rhashtable_walk_init - Initialise an iterator
  * @ht:		Table to walk over
  * @iter:	Hash table Iterator
+ * @gfp:	GFP flags for allocations
  *
  * This function prepares a hash table walk.
  *
@@ -504,14 +505,15 @@ EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
  * You must call rhashtable_walk_exit if this function returns
  * successfully.
  */
-int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter)
+int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter,
+			 gfp_t gfp)
 {
 	iter->ht = ht;
 	iter->p = NULL;
 	iter->slot = 0;
 	iter->skip = 0;
 
-	iter->walker = kmalloc(sizeof(*iter->walker), GFP_KERNEL);
+	iter->walker = kmalloc(sizeof(*iter->walker), gfp);
 	if (!iter->walker)
 		return -ENOMEM;
 
diff --git a/net/ipv6/ila/ila_xlat.c b/net/ipv6/ila/ila_xlat.c
index 295ca29a23c3..0b03533453e4 100644
--- a/net/ipv6/ila/ila_xlat.c
+++ b/net/ipv6/ila/ila_xlat.c
@@ -501,7 +501,8 @@ static int ila_nl_dump_start(struct netlink_callback *cb)
 	struct ila_net *ilan = net_generic(net, ila_net_id);
 	struct ila_dump_iter *iter = (struct ila_dump_iter *)cb->args;
 
-	return rhashtable_walk_init(&ilan->rhash_table, &iter->rhiter);
+	return rhashtable_walk_init(&ilan->rhash_table, &iter->rhiter,
+				    GFP_KERNEL);
 }
 
 static int ila_nl_dump_done(struct netlink_callback *cb)
diff --git a/net/netfilter/nft_hash.c b/net/netfilter/nft_hash.c
index 3f9d45d3d9b7..6fa016564f90 100644
--- a/net/netfilter/nft_hash.c
+++ b/net/netfilter/nft_hash.c
@@ -192,7 +192,7 @@ static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,
 	u8 genmask = nft_genmask_cur(read_pnet(&set->pnet));
 	int err;
 
-	err = rhashtable_walk_init(&priv->ht, &hti);
+	err = rhashtable_walk_init(&priv->ht, &hti, GFP_KERNEL);
 	iter->err = err;
 	if (err)
 		return;
@@ -248,7 +248,7 @@ static void nft_hash_gc(struct work_struct *work)
 	priv = container_of(work, struct nft_hash, gc_work.work);
 	set  = nft_set_container_of(priv);
 
-	err = rhashtable_walk_init(&priv->ht, &hti);
+	err = rhashtable_walk_init(&priv->ht, &hti, GFP_KERNEL);
 	if (err)
 		goto schedule;
 
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index c8416792cce0..6e0cbdeb21d3 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2335,7 +2335,8 @@ static int netlink_walk_start(struct nl_seq_iter *iter)
 {
 	int err;
 
-	err = rhashtable_walk_init(&nl_table[iter->link].hash, &iter->hti);
+	err = rhashtable_walk_init(&nl_table[iter->link].hash, &iter->hti,
+				   GFP_KERNEL);
 	if (err) {
 		iter->link = MAX_LINKS;
 		return err;
diff --git a/net/sctp/proc.c b/net/sctp/proc.c
index cfc3c7101a38..c5991e5e5daf 100644
--- a/net/sctp/proc.c
+++ b/net/sctp/proc.c
@@ -319,7 +319,8 @@ static int sctp_transport_walk_start(struct seq_file *seq)
 	struct sctp_ht_iter *iter = seq->private;
 	int err;
 
-	err = rhashtable_walk_init(&sctp_transport_hashtable, &iter->hti);
+	err = rhashtable_walk_init(&sctp_transport_hashtable, &iter->hti,
+				   GFP_KERNEL);
 	if (err)
 		return err;
 
-- 
2.6.1