netfs: Fix read-retry for fs with no ->prepare_read()

Fix netfslib's read-retry to only call ->prepare_read() in the backing
filesystem such a function is provided.  We can get to this point if a
there's an active cache as failed reads from the cache need negotiating
with the server instead.

Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/529329.1736261010@warthog.procyon.org.uk
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/netfs/read_retry.c b/fs/netfs/read_retry.c
index 21b4a54e545e1132abfd5e3df1b1f74fc76f617a..16b676c68dcd96b6a4d137b39ba0d096ea56d919 100644 (file)
--- a/fs/netfs/read_retry.c
+++ b/fs/netfs/read_retry.c
@@ -152,7 +152,8 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
                        BUG_ON(!len);
 
                        /* Renegotiate max_len (rsize) */
-                       if (rreq->netfs_ops->prepare_read(subreq) < 0) {
+                       if (rreq->netfs_ops->prepare_read &&
+                           rreq->netfs_ops->prepare_read(subreq) < 0) {
                                trace_netfs_sreq(subreq, netfs_sreq_trace_reprep_failed);
                                __set_bit(NETFS_SREQ_FAILED, &subreq->flags);
                        }