iscsi-target: Fix iscsi_np reset hung task during parallel delete

This patch fixes a bug associated with iscsit_reset_np_thread()
that can occur during parallel configfs rmdir of a single iscsi_np
used across multiple iscsi-target instances, that would result in
hung task(s) similar to below where configfs rmdir process context
was blocked indefinately waiting for iscsi_np->np_restart_comp
to finish:

[ 6726.112076] INFO: task dcp_proxy_node_:15550 blocked for more than 120 seconds.
[ 6726.119440]       Tainted: G        W  O     4.1.26-3321 #2
[ 6726.125045] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 6726.132927] dcp_proxy_node_ D ffff8803f202bc88     0 15550      1 0x00000000
[ 6726.140058]  ffff8803f202bc88 ffff88085c64d960 ffff88083b3b1ad0 ffff88087fffeb08
[ 6726.147593]  ffff8803f202c000 7fffffffffffffff ffff88083f459c28 ffff88083b3b1ad0
[ 6726.155132]  ffff88035373c100 ffff8803f202bca8 ffffffff8168ced2 ffff8803f202bcb8
[ 6726.162667] Call Trace:
[ 6726.165150]  [<ffffffff8168ced2>] schedule+0x32/0x80
[ 6726.170156]  [<ffffffff8168f5b4>] schedule_timeout+0x214/0x290
[ 6726.176030]  [<ffffffff810caef2>] ? __send_signal+0x52/0x4a0
[ 6726.181728]  [<ffffffff8168d7d6>] wait_for_completion+0x96/0x100
[ 6726.187774]  [<ffffffff810e7c80>] ? wake_up_state+0x10/0x10
[ 6726.193395]  [<ffffffffa035d6e2>] iscsit_reset_np_thread+0x62/0xe0 [iscsi_target_mod]
[ 6726.201278]  [<ffffffffa0355d86>] iscsit_tpg_disable_portal_group+0x96/0x190 [iscsi_target_mod]
[ 6726.210033]  [<ffffffffa0363f7f>] lio_target_tpg_store_enable+0x4f/0xc0 [iscsi_target_mod]
[ 6726.218351]  [<ffffffff81260c5a>] configfs_write_file+0xaa/0x110
[ 6726.224392]  [<ffffffff811ea364>] vfs_write+0xa4/0x1b0
[ 6726.229576]  [<ffffffff811eb111>] SyS_write+0x41/0xb0
[ 6726.234659]  [<ffffffff8169042e>] system_call_fastpath+0x12/0x71

It would happen because each iscsit_reset_np_thread() sets state
to ISCSI_NP_THREAD_RESET, sends SIGINT, and then blocks waiting
for completion on iscsi_np->np_restart_comp.

However, if iscsi_np was active processing a login request and
more than a single iscsit_reset_np_thread() caller to the same
iscsi_np was blocked on iscsi_np->np_restart_comp, iscsi_np
kthread process context in __iscsi_target_login_thread() would
flush pending signals and only perform a single completion of
np->np_restart_comp before going back to sleep within transport
specific iscsit_transport->iscsi_accept_np code.

To address this bug, add a iscsi_np->np_reset_count and update
__iscsi_target_login_thread() to keep completing np->np_restart_comp
until ->np_reset_count has reached zero.

Reported-by: Gary Guo <ghg@datera.io>
Tested-by: Gary Guo <ghg@datera.io>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 12803de99400b148043879b552acbdaf58763f5a..5001261f5d69d759dd25161401510551d35c3da7 100644 (file)
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -418,6 +418,7 @@ int iscsit_reset_np_thread(
                return 0;
        }
        np->np_thread_state = ISCSI_NP_THREAD_RESET;
+       atomic_inc(&np->np_reset_count);
 
        if (np->np_thread) {
                spin_unlock_bh(&np->np_thread_lock);

diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index e9bdc8b86e7d1d71d77cf4388370af6fcf3fded7..dc13afbd4c88dec2390ca8e65b3332d2f78acd73 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -1243,9 +1243,11 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
        flush_signals(current);
 
        spin_lock_bh(&np->np_thread_lock);
-       if (np->np_thread_state == ISCSI_NP_THREAD_RESET) {
+       if (atomic_dec_if_positive(&np->np_reset_count) >= 0) {
                np->np_thread_state = ISCSI_NP_THREAD_ACTIVE;
+               spin_unlock_bh(&np->np_thread_lock);
                complete(&np->np_restart_comp);
+               return 1;
        } else if (np->np_thread_state == ISCSI_NP_THREAD_SHUTDOWN) {
                spin_unlock_bh(&np->np_thread_lock);
                goto exit;
@@ -1278,7 +1280,8 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
                goto exit;
        } else if (rc < 0) {
                spin_lock_bh(&np->np_thread_lock);
-               if (np->np_thread_state == ISCSI_NP_THREAD_RESET) {
+               if (atomic_dec_if_positive(&np->np_reset_count) >= 0) {
+                       np->np_thread_state = ISCSI_NP_THREAD_ACTIVE;
                        spin_unlock_bh(&np->np_thread_lock);
                        complete(&np->np_restart_comp);
                        iscsit_put_transport(conn->conn_transport);

diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h
index 0ca1fb08805b254fa8ffda73f4decd4c48ac2211..fb87d32f5e513de3c2a1b7c6f402b5f48e401c45 100644 (file)
--- a/include/target/iscsi/iscsi_target_core.h
+++ b/include/target/iscsi/iscsi_target_core.h
@@ -786,6 +786,7 @@ struct iscsi_np {
        int                     np_sock_type;
        enum np_thread_state_table np_thread_state;
        bool                    enabled;
+       atomic_t                np_reset_count;
        enum iscsi_timer_flags_table np_login_timer_flags;
        u32                     np_exports;
        enum np_flags_table     np_flags;