[PATCH AUTOSEL 4.4 04/48] SUNRPC: Fix priority queue fairness

[PATCH AUTOSEL 4.4 04/48] SUNRPC: Fix priority queue fairness

[Sasha Levin]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

[ Upstream commit f42f7c283078ce3c1e8368b140e270755b1ae313 ]

Fix up the priority queue to not batch by owner, but by queue, so that
we allow '1 << priority' elements to be dequeued before switching to
the next priority queue.
The owner field is still used to wake up requests in round robin order
by owner to avoid single processes hogging the RPC layer by loading the
queues.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/sunrpc/sched.h |   2 -
 net/sunrpc/sched.c           | 109 +++++++++++++++++------------------
 2 files changed, 54 insertions(+), 57 deletions(-)

diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index d703f0ef37d8f..7d347e8cf944e 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -181,7 +181,6 @@ struct rpc_timer {
 struct rpc_wait_queue {
 	spinlock_t		lock;
 	struct list_head	tasks[RPC_NR_PRIORITY];	/* task queue for each priority level */
-	pid_t			owner;			/* process id of last task serviced */
 	unsigned char		maxpriority;		/* maximum priority (0 if queue is not a priority queue) */
 	unsigned char		priority;		/* current priority */
 	unsigned char		nr;			/* # tasks remaining for cookie */
@@ -197,7 +196,6 @@ struct rpc_wait_queue {
  * from a single cookie.  The aim is to improve
  * performance of NFS operations such as read/write.
  */
-#define RPC_BATCH_COUNT			16
 #define RPC_IS_PRIORITY(q)		((q)->maxpriority > 0)
 
 /*
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 1cb35c753dcda..3eed71a2ff2bb 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -98,64 +98,78 @@ __rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
 	list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list);
 }
 
-static void rpc_rotate_queue_owner(struct rpc_wait_queue *queue)
-{
-	struct list_head *q = &queue->tasks[queue->priority];
-	struct rpc_task *task;
-
-	if (!list_empty(q)) {
-		task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
-		if (task->tk_owner == queue->owner)
-			list_move_tail(&task->u.tk_wait.list, q);
-	}
-}
-
 static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
 {
 	if (queue->priority != priority) {
-		/* Fairness: rotate the list when changing priority */
-		rpc_rotate_queue_owner(queue);
 		queue->priority = priority;
+		queue->nr = 1U << priority;
 	}
 }
 
-static void rpc_set_waitqueue_owner(struct rpc_wait_queue *queue, pid_t pid)
-{
-	queue->owner = pid;
-	queue->nr = RPC_BATCH_COUNT;
-}
-
 static void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
 {
 	rpc_set_waitqueue_priority(queue, queue->maxpriority);
-	rpc_set_waitqueue_owner(queue, 0);
 }
 
 /*
- * Add new request to a priority queue.
+ * Add a request to a queue list
  */
-static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue,
-		struct rpc_task *task,
-		unsigned char queue_priority)
+static void
+__rpc_list_enqueue_task(struct list_head *q, struct rpc_task *task)
 {
-	struct list_head *q;
 	struct rpc_task *t;
 
-	INIT_LIST_HEAD(&task->u.tk_wait.links);
-	if (unlikely(queue_priority > queue->maxpriority))
-		queue_priority = queue->maxpriority;
-	if (queue_priority > queue->priority)
-		rpc_set_waitqueue_priority(queue, queue_priority);
-	q = &queue->tasks[queue_priority];
 	list_for_each_entry(t, q, u.tk_wait.list) {
 		if (t->tk_owner == task->tk_owner) {
-			list_add_tail(&task->u.tk_wait.list, &t->u.tk_wait.links);
+			list_add_tail(&task->u.tk_wait.links,
+					&t->u.tk_wait.links);
+			/* Cache the queue head in task->u.tk_wait.list */
+			task->u.tk_wait.list.next = q;
+			task->u.tk_wait.list.prev = NULL;
 			return;
 		}
 	}
+	INIT_LIST_HEAD(&task->u.tk_wait.links);
 	list_add_tail(&task->u.tk_wait.list, q);
 }
 
+/*
+ * Remove request from a queue list
+ */
+static void
+__rpc_list_dequeue_task(struct rpc_task *task)
+{
+	struct list_head *q;
+	struct rpc_task *t;
+
+	if (task->u.tk_wait.list.prev == NULL) {
+		list_del(&task->u.tk_wait.links);
+		return;
+	}
+	if (!list_empty(&task->u.tk_wait.links)) {
+		t = list_first_entry(&task->u.tk_wait.links,
+				struct rpc_task,
+				u.tk_wait.links);
+		/* Assume __rpc_list_enqueue_task() cached the queue head */
+		q = t->u.tk_wait.list.next;
+		list_add_tail(&t->u.tk_wait.list, q);
+		list_del(&task->u.tk_wait.links);
+	}
+	list_del(&task->u.tk_wait.list);
+}
+
+/*
+ * Add new request to a priority queue.
+ */
+static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue,
+		struct rpc_task *task,
+		unsigned char queue_priority)
+{
+	if (unlikely(queue_priority > queue->maxpriority))
+		queue_priority = queue->maxpriority;
+	__rpc_list_enqueue_task(&queue->tasks[queue_priority], task);
+}
+
 /*
  * Add new request to wait queue.
  *
@@ -193,13 +207,7 @@ static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
  */
 static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
 {
-	struct rpc_task *t;
-
-	if (!list_empty(&task->u.tk_wait.links)) {
-		t = list_entry(task->u.tk_wait.links.next, struct rpc_task, u.tk_wait.list);
-		list_move(&t->u.tk_wait.list, &task->u.tk_wait.list);
-		list_splice_init(&task->u.tk_wait.links, &t->u.tk_wait.links);
-	}
+	__rpc_list_dequeue_task(task);
 }
 
 /*
@@ -211,7 +219,8 @@ static void __rpc_remove_wait_queue(struct rpc_wait_queue *queue, struct rpc_tas
 	__rpc_disable_timer(queue, task);
 	if (RPC_IS_PRIORITY(queue))
 		__rpc_remove_wait_queue_priority(task);
-	list_del(&task->u.tk_wait.list);
+	else
+		list_del(&task->u.tk_wait.list);
 	queue->qlen--;
 	dprintk("RPC: %5u removed from queue %p \"%s\"\n",
 			task->tk_pid, queue, rpc_qname(queue));
@@ -467,17 +476,9 @@ static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *q
 	 * Service a batch of tasks from a single owner.
 	 */
 	q = &queue->tasks[queue->priority];
-	if (!list_empty(q)) {
-		task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
-		if (queue->owner == task->tk_owner) {
-			if (--queue->nr)
-				goto out;
-			list_move_tail(&task->u.tk_wait.list, q);
-		}
-		/*
-		 * Check if we need to switch queues.
-		 */
-		goto new_owner;
+	if (!list_empty(q) && --queue->nr) {
+		task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
+		goto out;
 	}
 
 	/*
@@ -489,7 +490,7 @@ static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *q
 		else
 			q = q - 1;
 		if (!list_empty(q)) {
-			task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
+			task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
 			goto new_queue;
 		}
 	} while (q != &queue->tasks[queue->priority]);
@@ -499,8 +500,6 @@ static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *q
 
 new_queue:
 	rpc_set_waitqueue_priority(queue, (unsigned int)(q - &queue->tasks[0]));
-new_owner:
-	rpc_set_waitqueue_owner(queue, task->tk_owner);
 out:
 	return task;
 }
-- 
2.20.1

[PATCH AUTOSEL 4.4 25/48] NFSv4.x: fix lock recovery during delegation recall

[Sasha Levin]

From: Olga Kornievskaia <kolga@netapp.com>

[ Upstream commit 44f411c353bf6d98d5a34f8f1b8605d43b2e50b8 ]

Running "./nfstest_delegation --runtest recall26" uncovers that
client doesn't recover the lock when we have an appending open,
where the initial open got a write delegation.

Instead of checking for the passed in open context against
the file lock's open context. Check that the state is the same.

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfs/delegation.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 7af5eeabc80e1..ee51e6f6c5d6e 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -91,7 +91,7 @@ int nfs4_check_delegation(struct inode *inode, fmode_t flags)
 	return nfs4_do_check_delegation(inode, flags, false);
 }
 
-static int nfs_delegation_claim_locks(struct nfs_open_context *ctx, struct nfs4_state *state, const nfs4_stateid *stateid)
+static int nfs_delegation_claim_locks(struct nfs4_state *state, const nfs4_stateid *stateid)
 {
 	struct inode *inode = state->inode;
 	struct file_lock *fl;
@@ -106,7 +106,7 @@ static int nfs_delegation_claim_locks(struct nfs_open_context *ctx, struct nfs4_
 	spin_lock(&flctx->flc_lock);
 restart:
 	list_for_each_entry(fl, list, fl_list) {
-		if (nfs_file_open_context(fl->fl_file) != ctx)
+		if (nfs_file_open_context(fl->fl_file)->state != state)
 			continue;
 		spin_unlock(&flctx->flc_lock);
 		status = nfs4_lock_delegation_recall(fl, state, stateid);
@@ -153,7 +153,7 @@ static int nfs_delegation_claim_opens(struct inode *inode,
 		seq = raw_seqcount_begin(&sp->so_reclaim_seqcount);
 		err = nfs4_open_delegation_recall(ctx, state, stateid, type);
 		if (!err)
-			err = nfs_delegation_claim_locks(ctx, state, stateid);
+			err = nfs_delegation_claim_locks(state, stateid);
 		if (!err && read_seqcount_retry(&sp->so_reclaim_seqcount, seq))
 			err = -EAGAIN;
 		mutex_unlock(&sp->so_delegreturn_mutex);
-- 
2.20.1