[PATCH v7 03/19] netfs: keep the prepare_read errno when abandoning read retries

[Paulo Alcantara <pc@manguebit.org>]

When ->prepare_read() fails while retrying a read,
netfs_retry_read_subrequests() marks the subrequest failed and abandons
the rest, which overwrites the error of every failed subrequest with
-ENOMEM.  The reader then gets -ENOMEM for e.g. a handle that couldn't be
reopened (-EHOSTDOWN, -ENOENT), a credit wait interrupted by a signal
(-ERESTARTSYS) or umount -f (-EIO).  The first pass doesn't have this
problem, as netfs_cancel_read() keeps the errno.

Record the errno of ->prepare_read() in the subrequest and keep the error
of subrequests that already failed, using -ENOMEM only for those
abandoned while still waiting for a retry.

Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: stable@vger.kernel.org
---
 fs/netfs/read_retry.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/netfs/read_retry.c b/fs/netfs/read_retry.c
index 5bd8dee5a834..8a722995fa9d 100644
--- a/fs/netfs/read_retry.c
+++ b/fs/netfs/read_retry.c
@@ -28,6 +28,7 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
 	struct netfs_io_subrequest *subreq;
 	struct netfs_io_stream *stream = &rreq->io_streams[0];
 	struct list_head *next;
+	int ret;
 
 	_enter("R=%x", rreq->debug_id);
 
@@ -140,8 +141,11 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
 
 			/* Renegotiate max_len (rsize) */
 			stream->sreq_max_len = subreq->len;
-			if (rreq->netfs_ops->prepare_read &&
-			    rreq->netfs_ops->prepare_read(subreq) < 0) {
+			ret = 0;
+			if (rreq->netfs_ops->prepare_read)
+				ret = rreq->netfs_ops->prepare_read(subreq);
+			if (ret < 0) {
+				subreq->error = ret;
 				trace_netfs_sreq(subreq, netfs_sreq_trace_reprep_failed);
 				__set_bit(NETFS_SREQ_FAILED, &subreq->flags);
 				goto abandon;
@@ -221,7 +225,9 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
 				part = netfs_limit_iter(&source, 0, part, stream->sreq_max_segs);
 
 			netfs_stat(&netfs_n_rh_download);
-			if (rreq->netfs_ops->prepare_read(subreq) < 0) {
+			ret = rreq->netfs_ops->prepare_read(subreq);
+			if (ret < 0) {
+				subreq->error = ret;
 				trace_netfs_sreq(subreq, netfs_sreq_trace_reprep_failed);
 				__set_bit(NETFS_SREQ_FAILED, &subreq->flags);
 				goto abandon;
@@ -257,7 +263,9 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
 		if (!test_bit(NETFS_SREQ_FAILED, &subreq->flags) &&
 		    !test_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags))
 			continue;
-		subreq->error = -ENOMEM;
+		if (!subreq->error ||
+		    !test_bit(NETFS_SREQ_FAILED, &subreq->flags))
+			subreq->error = -ENOMEM;
 		__set_bit(NETFS_SREQ_FAILED, &subreq->flags);
 		__clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
 	}
-- 
2.56.0