netfs: Provide helpers to perform NETFS_RREQ_IN_PROGRESS flag wangling

Provide helpers to clear and test the NETFS_RREQ_IN_PROGRESS and to insert
the appropriate barrierage.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/20250701163852.2171681-4-dhowells@redhat.com
Tested-by: Steve French <sfrench@samba.org>
Reviewed-by: Paulo Alcantara <pc@manguebit.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: dhowells

fs/netfs/internal.h

@@ -274,6 +274,24 @@ static inline void netfs_wake_rreq_flag(struct netfs_io_request *rreq,
 	}
 }
 
+/*
+ * Test the NETFS_RREQ_IN_PROGRESS flag, inserting an appropriate barrier.
+ */
+static inline bool netfs_check_rreq_in_progress(const struct netfs_io_request *rreq)
+{
+	/* Order read of flags before read of anything else, such as error. */
+	return test_bit_acquire(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
+}
+
+/*
+ * Test the NETFS_SREQ_IN_PROGRESS flag, inserting an appropriate barrier.
+ */
+static inline bool netfs_check_subreq_in_progress(const struct netfs_io_subrequest *subreq)
+{
+	/* Order read of flags before read of anything else, such as error. */
+	return test_bit_acquire(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
+}
+
 /*
  * fscache-cache.c
  */

fs/netfs/misc.c

@@ -356,14 +356,14 @@ void netfs_wait_for_in_progress_stream(struct netfs_io_request *rreq,
 	DEFINE_WAIT(myself);
 
 	list_for_each_entry(subreq, &stream->subrequests, rreq_link) {
-		if (!test_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags))
+		if (!netfs_check_subreq_in_progress(subreq))
 			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))
+			if (!netfs_check_subreq_in_progress(subreq))
 				break;
 
 			trace_netfs_sreq(subreq, netfs_sreq_trace_wait_for);
@@ -400,7 +400,7 @@ static int netfs_collect_in_app(struct netfs_io_request *rreq,
 						  struct netfs_io_subrequest,
 						  rreq_link);
 		if (subreq &&
-		    (!test_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags) ||
+		    (!netfs_check_subreq_in_progress(subreq) ||
 		     test_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags))) {
 			need_collect = true;
 			break;
@@ -451,7 +451,7 @@ static ssize_t netfs_wait_for_request(struct netfs_io_request *rreq,
 			}
 		}
 
-		if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
+		if (!netfs_check_rreq_in_progress(rreq))
 			break;
 
 		schedule();
@@ -518,7 +518,7 @@ static void netfs_wait_for_pause(struct netfs_io_request *rreq,
 			}
 		}
 
-		if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags) ||
+		if (!netfs_check_rreq_in_progress(rreq) ||
 		    !test_bit(NETFS_RREQ_PAUSE, &rreq->flags))
 			break;
 

fs/netfs/read_collect.c

@@ -218,7 +218,7 @@ static void netfs_collect_read_results(struct netfs_io_request *rreq)
 			stream->collected_to = front->start;
 		}
 
-		if (test_bit(NETFS_SREQ_IN_PROGRESS, &front->flags))
+		if (netfs_check_subreq_in_progress(front))
 			notes |= HIT_PENDING;
 		smp_rmb(); /* Read counters after IN_PROGRESS flag. */
 		transferred = READ_ONCE(front->transferred);
@@ -445,7 +445,7 @@ void netfs_read_collection_worker(struct work_struct *work)
 	struct netfs_io_request *rreq = container_of(work, struct netfs_io_request, work);
 
 	netfs_see_request(rreq, netfs_rreq_trace_see_work);
-	if (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags)) {
+	if (netfs_check_rreq_in_progress(rreq)) {
 		if (netfs_read_collection(rreq))
 			/* Drop the ref from the IN_PROGRESS flag. */
 			netfs_put_request(rreq, netfs_rreq_trace_put_work_ip);

fs/netfs/write_collect.c

@@ -240,7 +240,7 @@ static void netfs_collect_write_results(struct netfs_io_request *wreq)
 			}
 
 			/* Stall if the front is still undergoing I/O. */
-			if (test_bit(NETFS_SREQ_IN_PROGRESS, &front->flags)) {
+			if (netfs_check_subreq_in_progress(front)) {
 				notes |= HIT_PENDING;
 				break;
 			}
@@ -434,7 +434,7 @@ void netfs_write_collection_worker(struct work_struct *work)
 	struct netfs_io_request *rreq = container_of(work, struct netfs_io_request, work);
 
 	netfs_see_request(rreq, netfs_rreq_trace_see_work);
-	if (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags)) {
+	if (netfs_check_rreq_in_progress(rreq)) {
 		if (netfs_write_collection(rreq))
 			/* Drop the ref from the IN_PROGRESS flag. */
 			netfs_put_request(rreq, netfs_rreq_trace_put_work_ip);