[PATCH] nfsd: decrease cl_cb_inflight if fail to queue cb_work

[Li Lingfeng <lilingfeng3@huawei.com>]

In nfsd4_run_cb, cl_cb_inflight is increased before attempting to queue
cb_work to callback_wq. This count can be decreased in three situations:
1) If queuing fails in nfsd4_run_cb, the count will be decremented
accordingly.
2) After cb_work is running, the count is decreased in the exception
branch of nfsd4_run_cb_work via nfsd41_destroy_cb.
3) The count is decreased in the release callback of rpc_task — either
directly calling nfsd41_cb_inflight_end in nfsd4_cb_probe_release, or
calling nfsd41_destroy_cb in nfsd4_cb_release.

However, in nfsd4_cb_release, if the current cb_work needs to restart, the
count will not be decreased, with the expectation that it will be reduced
once cb_work is running.
If queuing fails here, then the count will leak, ultimately causing the
nfsd service to be unable to exit as shown below:
[root@nfs_test2 ~]# cat /proc/2271/stack
[<0>] nfsd4_shutdown_callback+0x22b/0x290
[<0>] __destroy_client+0x3cd/0x5c0
[<0>] nfs4_state_destroy_net+0xd2/0x330
[<0>] nfs4_state_shutdown_net+0x2ad/0x410
[<0>] nfsd_shutdown_net+0xb7/0x250
[<0>] nfsd_last_thread+0x15f/0x2a0
[<0>] nfsd_svc+0x388/0x3f0
[<0>] write_threads+0x17e/0x2b0
[<0>] nfsctl_transaction_write+0x91/0xf0
[<0>] vfs_write+0x1c4/0x750
[<0>] ksys_write+0xcb/0x170
[<0>] do_syscall_64+0x70/0x120
[<0>] entry_SYSCALL_64_after_hwframe+0x78/0xe2
[root@nfs_test2 ~]#

Fix this by decreasing cl_cb_inflight if the restart fails.

Fixes: cba5f62b1830 ("nfsd: fix callback restarts")
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
---
 fs/nfsd/nfs4callback.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 484077200c5d..8a7d24efdd08 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1459,12 +1459,16 @@ static void nfsd4_cb_done(struct rpc_task *task, void *calldata)
 static void nfsd4_cb_release(void *calldata)
 {
 	struct nfsd4_callback *cb = calldata;
+	struct nfs4_client *clp = cb->cb_clp;
+	int queued;
 
 	trace_nfsd_cb_rpc_release(cb->cb_clp);
 
-	if (cb->cb_need_restart)
-		nfsd4_queue_cb(cb);
-	else
+	if (cb->cb_need_restart) {
+		queued = nfsd4_queue_cb(cb);
+		if (!queued)
+			nfsd41_cb_inflight_end(clp);
+	} else
 		nfsd41_destroy_cb(cb);
 
 }
-- 
2.31.1