Re: [PATCH 3/3] nfsd: fix management of listener transports

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On 1/15/25 6:24 PM, Olga Kornievskaia wrote:
When a particular listener is being removed we need to make sure
that we delete the entry from the list of permanent sockets
(sv_permsocks) as well as remove it from the listener transports
(sp_xprts). When adding back the leftover transports not being
removed we need to clear XPT_BUSY flag so that it can be used.

Fixes: 16a471177496 ("NFSD: add listener-{set,get} netlink command")
Signed-off-by: Olga Kornievskaia <okorniev@xxxxxxxxxx>
---
  fs/nfsd/nfsctl.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 95ea4393305b..3deedd511e83 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1988,7 +1988,7 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
  	/* Close the remaining sockets on the permsocks list */
  	while (!list_empty(&permsocks)) {
  		xprt = list_first_entry(&permsocks, struct svc_xprt, xpt_list);
-		list_move(&xprt->xpt_list, &serv->sv_permsocks);
+		list_del_init(&xprt->xpt_list);
/*
  		 * Newly-created sockets are born with the BUSY bit set. Clear
@@ -2000,6 +2000,7 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
set_bit(XPT_CLOSE, &xprt->xpt_flags);
  		spin_unlock_bh(&serv->sv_lock);
+		svc_xprt_dequeue_entry(xprt);

The kdoc comment in front of llist_del_entry() says:

+ * The caller must ensure that nothing can race in and change the
+ * list while this is running.

In this caller, I don't see how such a race is prevented.


  		svc_xprt_close(xprt);
  		spin_lock_bh(&serv->sv_lock);
  	}
@@ -2031,6 +2032,7 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
xprt = svc_find_listener(serv, xcl_name, net, sa);
  		if (xprt) {
+			clear_bit(XPT_BUSY, &xprt->xpt_flags);
  			svc_xprt_put(xprt);
  			continue;
  		}


--
Chuck Lever




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