The netfs copy-to-cache that is used by Ceph with local caching sets up a new request to write data just read to the cache. The request is started and then left to look after itself whilst the app continues. The request gets notified by the backing fs upon completion of the async DIO write, but then tries to wake up the app because NETFS_RREQ_OFFLOAD_COLLECTION isn't set - but the app isn't waiting there, and so the request just hangs.

Fix this by setting NETFS_RREQ_OFFLOAD_COLLECTION which causes the notification from the backing filesystem to put the collection onto a work queue instead.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reported-by: Max Kellermann max.kellermann@ionos.com Link: https://lore.kernel.org/r/CAKPOu+8z_ijTLHdiCYGU_Uk7yYD=shxyGLwfe-L7AV3DhebS3... Signed-off-by: David Howells dhowells@redhat.com cc: Paulo Alcantara pc@manguebit.org cc: Viacheslav Dubeyko slava@dubeyko.com cc: Alex Markuze amarkuze@redhat.com cc: Ilya Dryomov idryomov@gmail.com cc: netfs@lists.linux.dev cc: ceph-devel@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: stable@vger.kernel.org --- fs/netfs/read_pgpriv2.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/fs/netfs/read_pgpriv2.c b/fs/netfs/read_pgpriv2.c index 5bbe906a551d..080d2a6a51d9 100644 --- a/fs/netfs/read_pgpriv2.c +++ b/fs/netfs/read_pgpriv2.c @@ -110,6 +110,7 @@ static struct netfs_io_request *netfs_pgpriv2_begin_copy_to_cache( if (!creq->io_streams[1].avail) goto cancel_put;

+ __set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &creq->flags); trace_netfs_write(creq, netfs_write_trace_copy_to_cache); netfs_stat(&netfs_n_wh_copy_to_cache); rreq->copy_to_cache = creq;