[PATCH v2 04/16] netfs: Fix looping in wait functions

[David Howells <dhowells@redhat.com>]

netfs_wait_for_request() and netfs_wait_for_pause() can loop forever if
netfs_collect_in_app() returns 2, indicating that it wants to repeat
because the ALL_QUEUED flag isn't yet set and there are no subreqs left
that haven't been collected.

The problem is that, unless collection is offloaded (OFFLOAD_COLLECTION),
we have to return to the application thread to continue and eventually set
ALL_QUEUED after pausing to deal with a retry - but we never get there.

Fix this by inserting checks for the IN_PROGRESS and PAUSE flags as
appropriate before cycling round - and add cond_resched() for good measure.

Fixes: 2b1424cd131c ("netfs: Fix wait/wake to be consistent about the waitqueue used")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Paulo Alcantara <pc@manguebit.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/misc.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index 7f31c3cbfe01..127a269938bb 100644
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -430,8 +430,8 @@ static int netfs_collect_in_app(struct netfs_io_request *rreq,
 /*
  * 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))
+static ssize_t netfs_wait_for_in_progress(struct netfs_io_request *rreq,
+					  bool (*collector)(struct netfs_io_request *rreq))
 {
 	DEFINE_WAIT(myself);
 	ssize_t ret;
@@ -447,6 +447,9 @@ static ssize_t netfs_wait_for_request(struct netfs_io_request *rreq,
 			case 1:
 				goto all_collected;
 			case 2:
+				if (!netfs_check_rreq_in_progress(rreq))
+					break;
+				cond_resched();
 				continue;
 			}
 		}
@@ -485,12 +488,12 @@ static ssize_t netfs_wait_for_request(struct netfs_io_request *rreq,
 
 ssize_t netfs_wait_for_read(struct netfs_io_request *rreq)
 {
-	return netfs_wait_for_request(rreq, netfs_read_collection);
+	return netfs_wait_for_in_progress(rreq, netfs_read_collection);
 }
 
 ssize_t netfs_wait_for_write(struct netfs_io_request *rreq)
 {
-	return netfs_wait_for_request(rreq, netfs_write_collection);
+	return netfs_wait_for_in_progress(rreq, netfs_write_collection);
 }
 
 /*
@@ -514,6 +517,10 @@ static void netfs_wait_for_pause(struct netfs_io_request *rreq,
 			case 1:
 				goto all_collected;
 			case 2:
+				if (!netfs_check_rreq_in_progress(rreq) ||
+				    !test_bit(NETFS_RREQ_PAUSE, &rreq->flags))
+					break;
+				cond_resched();
 				continue;
 			}
 		}