[PATCH v2] nvmet-fc: associations list protected by rcu, instead of spinlock_irq where possible.

From: leonid . ravich
Date: Sun Jan 03 2021 - 13:15:38 EST

From: Leonid Ravich <Leonid.Ravich@xxxxxxx>

searching assoc_list protected by rcu_read_lock if list not changed inline.
and according to the rcu list rules.

queue array embedded into nvmet_fc_tgt_assoc protected by rcu_read_lock
according to rcu dereference/assign rules.

queue and assoc object freed after grace period by call_rcu.

tgtport lock taken for changing assoc_list.

Reviewed-by: Eldad Zinger <Eldad.Zinger@xxxxxxxx>
Reviewed-by: Elad Grupi <Elad.Grupi@xxxxxxxx>
Signed-off-by: Leonid Ravich <Leonid.Ravich@xxxxxxx>
---
1) fixed sytle issus
2) queues array protects by rcu as well

drivers/nvme/target/fc.c | 81 +++++++++++++++++++++++-------------------------
1 file changed, 38 insertions(+), 43 deletions(-)

diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
index cd4e73a..c14c60b 100644
--- a/drivers/nvme/target/fc.c
+++ b/drivers/nvme/target/fc.c
@@ -145,6 +145,7 @@ struct nvmet_fc_tgt_queue {
struct list_head avail_defer_list;
struct workqueue_struct *work_q;
struct kref ref;
+ struct rcu_head rcu;
struct nvmet_fc_fcp_iod fod[]; /* array of fcp_iods */
} __aligned(sizeof(unsigned long long));

@@ -167,6 +168,7 @@ struct nvmet_fc_tgt_assoc {
struct nvmet_fc_tgt_queue *queues[NVMET_NR_QUEUES + 1];
struct kref ref;
struct work_struct del_work;
+ struct rcu_head rcu;
};


@@ -790,7 +792,6 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
u16 qid, u16 sqsize)
{
struct nvmet_fc_tgt_queue *queue;
- unsigned long flags;
int ret;

if (qid > NVMET_NR_QUEUES)
@@ -829,9 +830,7 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
goto out_fail_iodlist;

WARN_ON(assoc->queues[qid]);
- spin_lock_irqsave(&assoc->tgtport->lock, flags);
- assoc->queues[qid] = queue;
- spin_unlock_irqrestore(&assoc->tgtport->lock, flags);
+ rcu_assign_pointer(assoc->queues[qid], queue);

return queue;

@@ -851,11 +850,8 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
{
struct nvmet_fc_tgt_queue *queue =
container_of(ref, struct nvmet_fc_tgt_queue, ref);
- unsigned long flags;

- spin_lock_irqsave(&queue->assoc->tgtport->lock, flags);
- queue->assoc->queues[queue->qid] = NULL;
- spin_unlock_irqrestore(&queue->assoc->tgtport->lock, flags);
+ rcu_assign_pointer(queue->assoc->queues[queue->qid], NULL);

nvmet_fc_destroy_fcp_iodlist(queue->assoc->tgtport, queue);

@@ -863,7 +859,7 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,

destroy_workqueue(queue->work_q);

- kfree(queue);
+ kfree_rcu(queue, rcu);
}

static void
@@ -965,24 +961,23 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
struct nvmet_fc_tgt_queue *queue;
u64 association_id = nvmet_fc_getassociationid(connection_id);
u16 qid = nvmet_fc_getqueueid(connection_id);
- unsigned long flags;

if (qid > NVMET_NR_QUEUES)
return NULL;

- spin_lock_irqsave(&tgtport->lock, flags);
- list_for_each_entry(assoc, &tgtport->assoc_list, a_list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(assoc, &tgtport->assoc_list, a_list) {
if (association_id == assoc->association_id) {
- queue = assoc->queues[qid];
+ queue = rcu_dereference(assoc->queues[qid]);
if (queue &&
(!atomic_read(&queue->connected) ||
!nvmet_fc_tgt_q_get(queue)))
queue = NULL;
- spin_unlock_irqrestore(&tgtport->lock, flags);
+ rcu_read_unlock();
return queue;
}
}
- spin_unlock_irqrestore(&tgtport->lock, flags);
+ rcu_read_unlock();
return NULL;
}

@@ -1137,7 +1132,7 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
}
if (!needrandom) {
assoc->association_id = ran;
- list_add_tail(&assoc->a_list, &tgtport->assoc_list);
+ list_add_tail_rcu(&assoc->a_list, &tgtport->assoc_list);
}
spin_unlock_irqrestore(&tgtport->lock, flags);
}
@@ -1167,7 +1162,7 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,

nvmet_fc_free_hostport(assoc->hostport);
spin_lock_irqsave(&tgtport->lock, flags);
- list_del(&assoc->a_list);
+ list_del_rcu(&assoc->a_list);
oldls = assoc->rcv_disconn;
spin_unlock_irqrestore(&tgtport->lock, flags);
/* if pending Rcv Disconnect Association LS, send rsp now */
@@ -1177,7 +1172,7 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
dev_info(tgtport->dev,
"{%d:%d} Association freed\n",
tgtport->fc_target_port.port_num, assoc->a_id);
- kfree(assoc);
+ kfree_rcu(assoc, rcu);
nvmet_fc_tgtport_put(tgtport);
}

@@ -1198,7 +1193,6 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
{
struct nvmet_fc_tgtport *tgtport = assoc->tgtport;
struct nvmet_fc_tgt_queue *queue;
- unsigned long flags;
int i, terminating;

terminating = atomic_xchg(&assoc->terminating, 1);
@@ -1207,19 +1201,23 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
if (terminating)
return;

- spin_lock_irqsave(&tgtport->lock, flags);
+
for (i = NVMET_NR_QUEUES; i >= 0; i--) {
- queue = assoc->queues[i];
- if (queue) {
- if (!nvmet_fc_tgt_q_get(queue))
- continue;
- spin_unlock_irqrestore(&tgtport->lock, flags);
- nvmet_fc_delete_target_queue(queue);
- nvmet_fc_tgt_q_put(queue);
- spin_lock_irqsave(&tgtport->lock, flags);
+ rcu_read_lock();
+ queue = rcu_dereference(assoc->queues[i]);
+ if (!queue) {
+ rcu_read_unlock();
+ continue;
+ }
+
+ if (!nvmet_fc_tgt_q_get(queue)) {
+ rcu_read_unlock();
+ continue;
}
+ rcu_read_unlock();
+ nvmet_fc_delete_target_queue(queue);
+ nvmet_fc_tgt_q_put(queue);
}
- spin_unlock_irqrestore(&tgtport->lock, flags);

dev_info(tgtport->dev,
"{%d:%d} Association deleted\n",
@@ -1234,10 +1232,9 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
{
struct nvmet_fc_tgt_assoc *assoc;
struct nvmet_fc_tgt_assoc *ret = NULL;
- unsigned long flags;

- spin_lock_irqsave(&tgtport->lock, flags);
- list_for_each_entry(assoc, &tgtport->assoc_list, a_list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(assoc, &tgtport->assoc_list, a_list) {
if (association_id == assoc->association_id) {
ret = assoc;
if (!nvmet_fc_tgt_a_get(assoc))
@@ -1245,7 +1242,7 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
break;
}
}
- spin_unlock_irqrestore(&tgtport->lock, flags);
+ rcu_read_unlock();

return ret;
}
@@ -1473,19 +1470,17 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
static void
__nvmet_fc_free_assocs(struct nvmet_fc_tgtport *tgtport)
{
- struct nvmet_fc_tgt_assoc *assoc, *next;
- unsigned long flags;
+ struct nvmet_fc_tgt_assoc *assoc;

- spin_lock_irqsave(&tgtport->lock, flags);
- list_for_each_entry_safe(assoc, next,
- &tgtport->assoc_list, a_list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(assoc, &tgtport->assoc_list, a_list) {
if (!nvmet_fc_tgt_a_get(assoc))
continue;
if (!schedule_work(&assoc->del_work))
/* already deleting - release local reference */
nvmet_fc_tgt_a_put(assoc);
}
- spin_unlock_irqrestore(&tgtport->lock, flags);
+ rcu_read_unlock();
}

/**
@@ -1568,16 +1563,16 @@ static void nvmet_fc_xmt_ls_rsp(struct nvmet_fc_tgtport *tgtport,
continue;
spin_unlock_irqrestore(&nvmet_fc_tgtlock, flags);

- spin_lock_irqsave(&tgtport->lock, flags);
- list_for_each_entry(assoc, &tgtport->assoc_list, a_list) {
- queue = assoc->queues[0];
+ rcu_read_lock();
+ list_for_each_entry_rcu(assoc, &tgtport->assoc_list, a_list) {
+ queue = rcu_dereference(assoc->queues[0]);
if (queue && queue->nvme_sq.ctrl == ctrl) {
if (nvmet_fc_tgt_a_get(assoc))
found_ctrl = true;
break;
}
}
- spin_unlock_irqrestore(&tgtport->lock, flags);
+ rcu_read_unlock();

nvmet_fc_tgtport_put(tgtport);

--
1.9.3