1 files changed, 76 insertions, 27 deletions

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 5147d2213b01..cb60a42b9fdf 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -56,7 +56,8 @@ struct io_worker {
 
 	struct rcu_head rcu;
 	struct mm_struct *mm;
-	const struct cred *creds;
+	const struct cred *cur_creds;
+	const struct cred *saved_creds;
 	struct files_struct *restore_files;
 };
 
@@ -109,10 +110,10 @@ struct io_wq {
 
 	struct task_struct *manager;
 	struct user_struct *user;
-	const struct cred *creds;
-	struct mm_struct *mm;
 	refcount_t refs;
 	struct completion done;
+
+	refcount_t use_refs;
 };
 
 static bool io_worker_get(struct io_worker *worker)
@@ -135,9 +136,9 @@ static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker)
 {
 	bool dropped_lock = false;
 
-	if (worker->creds) {
-		revert_creds(worker->creds);
-		worker->creds = NULL;
+	if (worker->saved_creds) {
+		revert_creds(worker->saved_creds);
+		worker->cur_creds = worker->saved_creds = NULL;
 	}
 
 	if (current->files != worker->restore_files) {
@@ -396,6 +397,43 @@ static struct io_wq_work *io_get_next_work(struct io_wqe *wqe, unsigned *hash)
 	return NULL;
 }
 
+static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work *work)
+{
+	if (worker->mm) {
+		unuse_mm(worker->mm);
+		mmput(worker->mm);
+		worker->mm = NULL;
+	}
+	if (!work->mm) {
+		set_fs(KERNEL_DS);
+		return;
+	}
+	if (mmget_not_zero(work->mm)) {
+		use_mm(work->mm);
+		if (!worker->mm)
+			set_fs(USER_DS);
+		worker->mm = work->mm;
+		/* hang on to this mm */
+		work->mm = NULL;
+		return;
+	}
+
+	/* failed grabbing mm, ensure work gets cancelled */
+	work->flags |= IO_WQ_WORK_CANCEL;
+}
+
+static void io_wq_switch_creds(struct io_worker *worker,
+			       struct io_wq_work *work)
+{
+	const struct cred *old_creds = override_creds(work->creds);
+
+	worker->cur_creds = work->creds;
+	if (worker->saved_creds)
+		put_cred(old_creds); /* creds set by previous switch */
+	else
+		worker->saved_creds = old_creds;
+}
+
 static void io_worker_handle_work(struct io_worker *worker)
 	__releases(wqe->lock)
 {
@@ -438,24 +476,19 @@ next:
 		if (work->flags & IO_WQ_WORK_CB)
 			work->func(&work);
 
-		if ((work->flags & IO_WQ_WORK_NEEDS_FILES) &&
-		    current->files != work->files) {
+		if (work->files && current->files != work->files) {
 			task_lock(current);
 			current->files = work->files;
 			task_unlock(current);
 		}
-		if ((work->flags & IO_WQ_WORK_NEEDS_USER) && !worker->mm &&
-		    wq->mm) {
-			if (mmget_not_zero(wq->mm)) {
-				use_mm(wq->mm);
-				set_fs(USER_DS);
-				worker->mm = wq->mm;
-			} else {
-				work->flags |= IO_WQ_WORK_CANCEL;
-			}
-		}
-		if (!worker->creds)
-			worker->creds = override_creds(wq->creds);
+		if (work->mm != worker->mm)
+			io_wq_switch_mm(worker, work);
+		if (worker->cur_creds != work->creds)
+			io_wq_switch_creds(worker, work);
+		/*
+		 * OK to set IO_WQ_WORK_CANCEL even for uncancellable work,
+		 * the worker function will do the right thing.
+		 */
 		if (test_bit(IO_WQ_BIT_CANCEL, &wq->state))
 			work->flags |= IO_WQ_WORK_CANCEL;
 		if (worker->mm)
@@ -720,6 +753,7 @@ static bool io_wq_can_queue(struct io_wqe *wqe, struct io_wqe_acct *acct,
 static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
 {
 	struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
+	int work_flags;
 	unsigned long flags;
 
 	/*
@@ -734,12 +768,14 @@ static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
 		return;
 	}
 
+	work_flags = work->flags;
 	spin_lock_irqsave(&wqe->lock, flags);
 	wq_list_add_tail(&work->list, &wqe->work_list);
 	wqe->flags &= ~IO_WQE_FLAG_STALLED;
 	spin_unlock_irqrestore(&wqe->lock, flags);
 
-	if (!atomic_read(&acct->nr_running))
+	if ((work_flags & IO_WQ_WORK_CONCURRENT) ||
+	    !atomic_read(&acct->nr_running))
 		io_wqe_wake_worker(wqe, acct);
 }
 
@@ -828,6 +864,7 @@ static bool io_work_cancel(struct io_worker *worker, void *cancel_data)
 	 */
 	spin_lock_irqsave(&worker->lock, flags);
 	if (worker->cur_work &&
+	    !(worker->cur_work->flags & IO_WQ_WORK_NO_CANCEL) &&
 	    data->cancel(worker->cur_work, data->caller_data)) {
 		send_sig(SIGINT, worker->task, 1);
 		ret = true;
@@ -902,7 +939,8 @@ static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
 		return false;
 
 	spin_lock_irqsave(&worker->lock, flags);
-	if (worker->cur_work == work) {
+	if (worker->cur_work == work &&
+	    !(worker->cur_work->flags & IO_WQ_WORK_NO_CANCEL)) {
 		send_sig(SIGINT, worker->task, 1);
 		ret = true;
 	}
@@ -1026,7 +1064,6 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 
 	/* caller must already hold a reference to this */
 	wq->user = data->user;
-	wq->creds = data->creds;
 
 	for_each_node(node) {
 		struct io_wqe *wqe;
@@ -1053,9 +1090,6 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 
 	init_completion(&wq->done);
 
-	/* caller must have already done mmgrab() on this mm */
-	wq->mm = data->mm;
-
 	wq->manager = kthread_create(io_wq_manager, wq, "io_wq_manager");
 	if (!IS_ERR(wq->manager)) {
 		wake_up_process(wq->manager);
@@ -1064,6 +1098,7 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 			ret = -ENOMEM;
 			goto err;
 		}
+		refcount_set(&wq->use_refs, 1);
 		reinit_completion(&wq->done);
 		return wq;
 	}
@@ -1078,13 +1113,21 @@ err:
 	return ERR_PTR(ret);
 }
 
+bool io_wq_get(struct io_wq *wq, struct io_wq_data *data)
+{
+	if (data->get_work != wq->get_work || data->put_work != wq->put_work)
+		return false;
+
+	return refcount_inc_not_zero(&wq->use_refs);
+}
+
 static bool io_wq_worker_wake(struct io_worker *worker, void *data)
 {
 	wake_up_process(worker->task);
 	return false;
 }
 
-void io_wq_destroy(struct io_wq *wq)
+static void __io_wq_destroy(struct io_wq *wq)
 {
 	int node;
 
@@ -1104,3 +1147,9 @@ void io_wq_destroy(struct io_wq *wq)
 	kfree(wq->wqes);
 	kfree(wq);
 }
+
+void io_wq_destroy(struct io_wq *wq)
+{
+	if (refcount_dec_and_test(&wq->use_refs))
+		__io_wq_destroy(wq);
+}