netfs: Fix wait/wake to be consistent about the waitqueue used

Fix further inconsistencies in the use of waitqueues
(clear_and_wake_up_bit() vs private waitqueue).

Move some of this stuff from the read and write sides into common code so
that it can be done in fewer places.

To make this work, async I/O needs to set NETFS_RREQ_OFFLOAD_COLLECTION to
indicate that a workqueue will do the collecting and places that call the
wait function need to deal with it returning the amount transferred.

Fixes: e2d46f2 ("netfs: Change the read result collector to only use one work item")
Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Steve French <[email protected]>
cc: Ihor Solodrai <[email protected]>
cc: Eric Van Hensbergen <[email protected]>
cc: Latchesar Ionkov <[email protected]>
cc: Dominique Martinet <[email protected]>
cc: Christian Schoenebeck <[email protected]>
cc: Paulo Alcantara <[email protected]>
cc: Jeff Layton <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
Signed-off-by: Steve French <[email protected]>

fs/netfs/buffered_read.c

@@ -312,7 +312,7 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
 	if (unlikely(size > 0)) {
 		smp_wmb(); /* Write lists before ALL_QUEUED. */
 		set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags);
-		netfs_wake_read_collector(rreq);
+		netfs_wake_collector(rreq);
 	}
 
 	/* Defer error return as we may need to wait for outstanding I/O. */

fs/netfs/buffered_write.c

@@ -386,7 +386,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		wbc_detach_inode(&wbc);
 		if (ret2 == -EIOCBQUEUED)
 			return ret2;
-		if (ret == 0)
+		if (ret == 0 && ret2 < 0)
 			ret = ret2;
 	}
 

fs/netfs/direct_read.c

@@ -103,7 +103,7 @@ static int netfs_dispatch_unbuffered_reads(struct netfs_io_request *rreq)
 		rreq->netfs_ops->issue_read(subreq);
 
 		if (test_bit(NETFS_RREQ_PAUSE, &rreq->flags))
-			netfs_wait_for_pause(rreq);
+			netfs_wait_for_paused_read(rreq);
 		if (test_bit(NETFS_RREQ_FAILED, &rreq->flags))
 			break;
 		if (test_bit(NETFS_RREQ_BLOCKED, &rreq->flags) &&
@@ -115,7 +115,7 @@ static int netfs_dispatch_unbuffered_reads(struct netfs_io_request *rreq)
 	if (unlikely(size > 0)) {
 		smp_wmb(); /* Write lists before ALL_QUEUED. */
 		set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags);
-		netfs_wake_read_collector(rreq);
+		netfs_wake_collector(rreq);
 	}
 
 	return ret;

fs/netfs/direct_write.c

@@ -87,6 +87,8 @@ ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *
 	}
 
 	__set_bit(NETFS_RREQ_USE_IO_ITER, &wreq->flags);
+	if (async)
+		__set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &wreq->flags);
 
 	/* Copy the data into the bounce buffer and encrypt it. */
 	// TODO
@@ -105,13 +107,9 @@ ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *
 
 	if (!async) {
 		trace_netfs_rreq(wreq, netfs_rreq_trace_wait_ip);
-		wait_on_bit(&wreq->flags, NETFS_RREQ_IN_PROGRESS,
-			    TASK_UNINTERRUPTIBLE);
-		ret = wreq->error;
-		if (ret == 0) {
-			ret = wreq->transferred;
+		ret = netfs_wait_for_write(wreq);
+		if (ret > 0)
 			iocb->ki_pos += ret;
-		}
 	} else {
 		ret = -EIOCBQUEUED;
 	}

fs/netfs/internal.h

@@ -62,6 +62,14 @@ static inline void netfs_proc_del_rreq(struct netfs_io_request *rreq) {}
 struct folio_queue *netfs_buffer_make_space(struct netfs_io_request *rreq,
 					    enum netfs_folioq_trace trace);
 void netfs_reset_iter(struct netfs_io_subrequest *subreq);
+void netfs_wake_collector(struct netfs_io_request *rreq);
+void netfs_subreq_clear_in_progress(struct netfs_io_subrequest *subreq);
+void netfs_wait_for_in_progress_stream(struct netfs_io_request *rreq,
+				       struct netfs_io_stream *stream);
+ssize_t netfs_wait_for_read(struct netfs_io_request *rreq);
+ssize_t netfs_wait_for_write(struct netfs_io_request *rreq);
+void netfs_wait_for_paused_read(struct netfs_io_request *rreq);
+void netfs_wait_for_paused_write(struct netfs_io_request *rreq);
 
 /*
  * objects.c
@@ -91,11 +99,9 @@ static inline void netfs_see_subrequest(struct netfs_io_subrequest *subreq,
 /*
  * read_collect.c
  */
+bool netfs_read_collection(struct netfs_io_request *rreq);
 void netfs_read_collection_worker(struct work_struct *work);
-void netfs_wake_read_collector(struct netfs_io_request *rreq);
 void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error);
-ssize_t netfs_wait_for_read(struct netfs_io_request *rreq);
-void netfs_wait_for_pause(struct netfs_io_request *rreq);
 
 /*
  * read_pgpriv2.c
@@ -175,8 +181,8 @@ static inline void netfs_stat_d(atomic_t *stat)
  * write_collect.c
  */
 int netfs_folio_written_back(struct folio *folio);
+bool netfs_write_collection(struct netfs_io_request *wreq);
 void netfs_write_collection_worker(struct work_struct *work);
-void netfs_wake_write_collector(struct netfs_io_request *wreq);
 
 /*
  * write_issue.c
@@ -197,8 +203,8 @@ struct netfs_io_request *netfs_begin_writethrough(struct kiocb *iocb, size_t len
 int netfs_advance_writethrough(struct netfs_io_request *wreq, struct writeback_control *wbc,
 			       struct folio *folio, size_t copied, bool to_page_end,
 			       struct folio **writethrough_cache);
-int netfs_end_writethrough(struct netfs_io_request *wreq, struct writeback_control *wbc,
-			   struct folio *writethrough_cache);
+ssize_t netfs_end_writethrough(struct netfs_io_request *wreq, struct writeback_control *wbc,
+			       struct folio *writethrough_cache);
 int netfs_unbuffered_write(struct netfs_io_request *wreq, bool may_wait, size_t len);
 
 /*
@@ -253,6 +259,21 @@ static inline void netfs_put_group_many(struct netfs_group *netfs_group, int nr)
 		netfs_group->free(netfs_group);
 }
 
+/*
+ * Clear and wake up a NETFS_RREQ_* flag bit on a request.
+ */
+static inline void netfs_wake_rreq_flag(struct netfs_io_request *rreq,
+					unsigned int rreq_flag,
+					enum netfs_rreq_trace trace)
+{
+	if (test_bit(rreq_flag, &rreq->flags)) {
+		trace_netfs_rreq(rreq, trace);
+		clear_bit_unlock(rreq_flag, &rreq->flags);
+		smp_mb__after_atomic(); /* Set flag before task state */
+		wake_up(&rreq->waitq);
+	}
+}
+
 /*
  * fscache-cache.c
  */

fs/netfs/misc.c

@@ -313,3 +313,220 @@ bool netfs_release_folio(struct folio *folio, gfp_t gfp)
 	return true;
 }
 EXPORT_SYMBOL(netfs_release_folio);
+
+/*
+ * Wake the collection work item.
+ */
+void netfs_wake_collector(struct netfs_io_request *rreq)
+{
+	if (test_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags) &&
+	    !test_bit(NETFS_RREQ_RETRYING, &rreq->flags)) {
+		queue_work(system_unbound_wq, &rreq->work);
+	} else {
+		trace_netfs_rreq(rreq, netfs_rreq_trace_wake_queue);
+		wake_up(&rreq->waitq);
+	}
+}
+
+/*
+ * Mark a subrequest as no longer being in progress and, if need be, wake the
+ * collector.
+ */
+void netfs_subreq_clear_in_progress(struct netfs_io_subrequest *subreq)
+{
+	struct netfs_io_request *rreq = subreq->rreq;
+	struct netfs_io_stream *stream = &rreq->io_streams[subreq->stream_nr];
+
+	clear_bit_unlock(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
+	smp_mb__after_atomic(); /* Clear IN_PROGRESS before task state */
+
+	/* If we are at the head of the queue, wake up the collector. */
+	if (list_is_first(&subreq->rreq_link, &stream->subrequests) ||
+	    test_bit(NETFS_RREQ_RETRYING, &rreq->flags))
+		netfs_wake_collector(rreq);
+}
+
+/*
+ * Wait for all outstanding I/O in a stream to quiesce.
+ */
+void netfs_wait_for_in_progress_stream(struct netfs_io_request *rreq,
+				       struct netfs_io_stream *stream)
+{
+	struct netfs_io_subrequest *subreq;
+	DEFINE_WAIT(myself);
+
+	list_for_each_entry(subreq, &stream->subrequests, rreq_link) {
+		if (!test_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags))
+			continue;
+
+		trace_netfs_rreq(rreq, netfs_rreq_trace_wait_queue);
+		for (;;) {
+			prepare_to_wait(&rreq->waitq, &myself, TASK_UNINTERRUPTIBLE);
+
+			if (!test_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags))
+				break;
+
+			trace_netfs_sreq(subreq, netfs_sreq_trace_wait_for);
+			schedule();
+			trace_netfs_rreq(rreq, netfs_rreq_trace_woke_queue);
+		}
+	}
+
+	finish_wait(&rreq->waitq, &myself);
+}
+
+/*
+ * Perform collection in app thread if not offloaded to workqueue.
+ */
+static int netfs_collect_in_app(struct netfs_io_request *rreq,
+				bool (*collector)(struct netfs_io_request *rreq))
+{
+	bool need_collect = false, inactive = true;
+
+	for (int i = 0; i < NR_IO_STREAMS; i++) {
+		struct netfs_io_subrequest *subreq;
+		struct netfs_io_stream *stream = &rreq->io_streams[i];
+
+		if (!stream->active)
+			continue;
+		inactive = false;
+		trace_netfs_collect_stream(rreq, stream);
+		subreq = list_first_entry_or_null(&stream->subrequests,
+						  struct netfs_io_subrequest,
+						  rreq_link);
+		if (subreq &&
+		    (!test_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags) ||
+		     test_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags))) {
+			need_collect = true;
+			break;
+		}
+	}
+
+	if (!need_collect && !inactive)
+		return 0; /* Sleep */
+
+	__set_current_state(TASK_RUNNING);
+	if (collector(rreq)) {
+		/* Drop the ref from the NETFS_RREQ_IN_PROGRESS flag. */
+		netfs_put_request(rreq, netfs_rreq_trace_put_work_ip);
+		return 1; /* Done */
+	}
+
+	if (inactive) {
+		WARN(true, "Failed to collect inactive req R=%08x\n",
+		     rreq->debug_id);
+		cond_resched();
+	}
+	return 2; /* Again */
+}
+
+/*
+ * Wait for a request to complete, successfully or otherwise.
+ */
+static ssize_t netfs_wait_for_request(struct netfs_io_request *rreq,
+				      bool (*collector)(struct netfs_io_request *rreq))
+{
+	DEFINE_WAIT(myself);
+	ssize_t ret;
+
+	for (;;) {
+		trace_netfs_rreq(rreq, netfs_rreq_trace_wait_queue);
+		prepare_to_wait(&rreq->waitq, &myself, TASK_UNINTERRUPTIBLE);
+
+		if (!test_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags)) {
+			switch (netfs_collect_in_app(rreq, collector)) {
+			case 0:
+				break;
+			case 1:
+				goto all_collected;
+			case 2:
+				continue;
+			}
+		}
+
+		if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
+			break;
+
+		schedule();
+		trace_netfs_rreq(rreq, netfs_rreq_trace_woke_queue);
+	}
+
+all_collected:
+	finish_wait(&rreq->waitq, &myself);
+
+	ret = rreq->error;
+	if (ret == 0) {
+		ret = rreq->transferred;
+		switch (rreq->origin) {
+		case NETFS_DIO_READ:
+		case NETFS_DIO_WRITE:
+		case NETFS_READ_SINGLE:
+			break;
+		default:
+			if (rreq->submitted < rreq->len) {
+				trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_read);
+				ret = -EIO;
+			}
+			break;
+		}
+	}
+
+	return ret;
+}
+
+ssize_t netfs_wait_for_read(struct netfs_io_request *rreq)
+{
+	return netfs_wait_for_request(rreq, netfs_read_collection);
+}
+
+ssize_t netfs_wait_for_write(struct netfs_io_request *rreq)
+{
+	return netfs_wait_for_request(rreq, netfs_write_collection);
+}
+
+/*
+ * Wait for a paused operation to unpause or complete in some manner.
+ */
+static void netfs_wait_for_pause(struct netfs_io_request *rreq,
+				 bool (*collector)(struct netfs_io_request *rreq))
+{
+	DEFINE_WAIT(myself);
+
+	trace_netfs_rreq(rreq, netfs_rreq_trace_wait_pause);
+
+	for (;;) {
+		trace_netfs_rreq(rreq, netfs_rreq_trace_wait_queue);
+		prepare_to_wait(&rreq->waitq, &myself, TASK_UNINTERRUPTIBLE);
+
+		if (!test_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags)) {
+			switch (netfs_collect_in_app(rreq, collector)) {
+			case 0:
+				break;
+			case 1:
+				goto all_collected;
+			case 2:
+				continue;
+			}
+		}
+
+		if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags) ||
+		    !test_bit(NETFS_RREQ_PAUSE, &rreq->flags))
+			break;
+
+		schedule();
+		trace_netfs_rreq(rreq, netfs_rreq_trace_woke_queue);
+	}
+
+all_collected:
+	finish_wait(&rreq->waitq, &myself);
+}
+
+void netfs_wait_for_paused_read(struct netfs_io_request *rreq)
+{
+	return netfs_wait_for_pause(rreq, netfs_read_collection);
+}
+
+void netfs_wait_for_paused_write(struct netfs_io_request *rreq)
+{
+	return netfs_wait_for_pause(rreq, netfs_write_collection);
+}