ceph: fix cap ref leak via netfs init_request

Log recovered from a user's cluster:

<7>[ 5413.970692] ceph: get_cap_refs 00000000958c114b ret 1 got Fr
<7>[ 5413.970695] ceph: start_read 00000000958c114b, no cache cap
...
<7>[ 5473.934609] ceph: my wanted = Fr, used = Fr, dirty -
<7>[ 5473.934616] ceph: revocation: pAsLsXsFr -> pAsLsXs (revoking Fr)
<7>[ 5473.934632] ceph: __ceph_caps_issued 00000000958c114b cap 00000000f7784259 issued pAsLsXs
<7>[ 5473.934638] ceph: check_caps 10000000e68.fffffffffffffffe file_want - used Fr dirty - flushing - issued pAsLsXs revoking Fr retain pAsLsXsFsr AUTHONLY NOINVAL FLUSH_FORCE

The MDS subsequently complains that the kernel client is late releasing
caps.

Approximately, a series of changes to this code by commits 49870056005c
("ceph: convert ceph_readpages to ceph_readahead"), 2de160417315
("netfs: Change ->init_request() to return an error code") and
a5c9dc445139 ("ceph: Make ceph_init_request() check caps on readahead")
resulted in subtle resource cleanup to be missed. The main culprit is
the change in error handling in 2de160417315 which meant that a failure
in init_request() would no longer cause cleanup to be called. That
would prevent the ceph_put_cap_refs() call which would cleanup the
leaked cap ref.

Cc: [e-mail]
Fixes: a5c9dc445139 ("ceph: Make ceph_init_request() check caps on readahead")
Link: https://tracker.ceph.com/issues/67008
Signed-off-by: Patrick Donnelly <[e-mail]>
Reviewed-by: Ilya Dryomov <[e-mail]>
Signed-off-by: Ilya Dryomov <[e-mail]>

fs/ceph/addr.c

···
 	rreq->io_streams[0].sreq_max_len = fsc->mount_options->rsize;
 
 out:
-	if (ret < 0)
+	if (ret < 0) {
+		if (got)
+			ceph_put_cap_refs(ceph_inode(inode), got);
 		kfree(priv);
+	}
 
 	return ret;
 }