When an iscsi initiator is connected to a target running on the
same machine, the system may trigger a deadlock when working
under memory pressure.
This may happen, for example, when the iscsi rx thread tries to
allocate memory and a memory reclaim is performed, the rx thread may
therefore end up waiting for the initiator to complete I/O operations,
causing a deadlock.
Fix the issue by using memalloc_noio_*() to enable implicit GFP_NOIO
in the vulnerable code paths, when the connection is in loopback.
Suggested-by: David Jeffery <djeffery@xxxxxxxxxx>
Signed-off-by: Maurizio Lombardi <mlombard@xxxxxxxxxx>
---
drivers/target/iscsi/iscsi_target.c | 19 ++++++++++++++++---
drivers/target/iscsi/iscsi_target_login.c | 8 ++++++++
include/target/iscsi/iscsi_target_core.h | 1 +
3 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index baf4da7bb3b4..4d997a049bf7 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -3918,9 +3918,9 @@ static int iscsit_handle_response_queue(struct iscsit_conn *conn)
int iscsi_target_tx_thread(void *arg)
{
- int ret = 0;
+ int ret = 0, flags;
struct iscsit_conn *conn = arg;
- bool conn_freed = false;
+ bool conn_freed = false, loopback;
/*
* Allow ourselves to be interrupted by SIGINT so that a
@@ -3928,6 +3928,10 @@ int iscsi_target_tx_thread(void *arg)
*/
allow_signal(SIGINT);
+ loopback = conn->loopback;
+ if (loopback)
+ flags = memalloc_noio_save();
+
while (!kthread_should_stop()) {
/*
* Ensure that both TX and RX per connection kthreads
@@ -3966,6 +3970,9 @@ int iscsi_target_tx_thread(void *arg)
if (conn->conn_state != TARG_CONN_STATE_IN_LOGIN)
iscsit_take_action_for_connection_exit(conn, &conn_freed);
out:
+ if (loopback)
+ memalloc_noio_restore(flags);
+
if (!conn_freed) {
while (!kthread_should_stop()) {
msleep(100);
@@ -4166,7 +4173,7 @@ static void iscsit_get_rx_pdu(struct iscsit_conn *conn)
int iscsi_target_rx_thread(void *arg)
{
- int rc;
+ int rc, flags;
struct iscsit_conn *conn = arg;
bool conn_freed = false;
@@ -4186,8 +4193,14 @@ int iscsi_target_rx_thread(void *arg)
if (!conn->conn_transport->iscsit_get_rx_pdu)
return 0;
+ if (conn->loopback)
+ flags = memalloc_noio_save();
+
conn->conn_transport->iscsit_get_rx_pdu(conn);
+ if (conn->loopback)
+ memalloc_noio_restore(flags);
+
if (!signal_pending(current))
atomic_set(&conn->transport_failed, 1);
iscsit_take_action_for_connection_exit(conn, &conn_freed);
diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index 27e448c2d066..bbda125f6526 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -17,6 +17,7 @@
#include <linux/tcp.h> /* TCP_NODELAY */
#include <net/ip.h>
#include <net/ipv6.h> /* ipv6_addr_v4mapped() */
+#include <net/sock.h>
#include <scsi/iscsi_proto.h>
#include <target/target_core_base.h>
#include <target/target_core_fabric.h>
@@ -1246,6 +1247,7 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
struct iscsi_portal_group *tpg = NULL;
struct iscsi_login_req *pdu;
struct iscsi_tpg_np *tpg_np;
+ struct dst_entry *dst;
bool new_sess = false;
flush_signals(current);
@@ -1289,6 +1291,12 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
iscsit_free_conn(conn);
return 1;
}
+
+ dst = sk_dst_get(conn->sock->sk);
+ if (dst && dst->dev && dst->dev->flags & IFF_LOOPBACK)
+ conn->loopback = true;
+ dst_release(dst);
+
/*
* Perform the remaining iSCSI connection initialization items..
*/
diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h
index 94d06ddfd80a..aa8d4026e32e 100644
--- a/include/target/iscsi/iscsi_target_core.h
+++ b/include/target/iscsi/iscsi_target_core.h
@@ -538,6 +538,7 @@ struct iscsit_conn {
struct sockaddr_storage local_sockaddr;
int conn_usage_count;
int conn_waiting_on_uc;
+ bool loopback;
atomic_t check_immediate_queue;
atomic_t conn_logout_remove;
atomic_t connection_exit;
--
2.31.1
