Re: [PATCH v2 2/2] NFSD: limit the number of v4 clients to 1024 per 1GB of system memory

From: Geert Uytterhoeven
Date: Fri Jul 15 2022 - 09:05:57 EST

Hi Dai,

On Thu, 14 Jul 2022, Dai Ngo wrote:
Currently there is no limit on how many v4 clients are supported
by the system. This can be a problem in systems with small memory
configuration to function properly when a very large number of
clients exist that creates memory shortage conditions.

This patch enforces a limit of 1024 NFSv4 clients, including courtesy
clients, per 1GB of system memory. When the number of the clients
reaches the limit, requests that create new clients are returned
with NFS4ERR_DELAY and the laundromat is kicked start to trim old
clients. Due to the overhead of the upcall to remove the client
record, the maximun number of clients the laundromat removes on
each run is limited to 128. This is done to ensure the laundromat
can still process the other tasks in a timely manner.

Since there is now a limit of the number of clients, the 24-hr
idle time limit of courtesy client is no longer needed and was

Signed-off-by: Dai Ngo <>

Thanks for your patch, which is now commit 05eaba9bd8c06580 ("NFSD:
limit the number of v4 clients to 1024 per 1GB of system memory")
in next-20220715.

noreply@xxxxxxxxxxxxxx reports:

fs/nfsd/nfsctl.c:1504:24: error: 'NFS4_CLIENTS_PER_GB' undeclared (first use in this function)

--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1463,6 +1463,8 @@ static __net_init int nfsd_init_net(struct net *net)
int retval;
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ u64 max_clients;
+ struct sysinfo si;

retval = nfsd_export_init(net);
if (retval)
@@ -1488,6 +1490,10 @@ static __net_init int nfsd_init_net(struct net *net)

Not protected by #ifdef CONFIG_NFSD_V4:


atomic_set(&nn->nfs4_client_count, 0);
+ si_meminfo(&si);
+ max_clients = (u64)si.totalram * si.mem_unit / (1024 * 1024 * 1024);
+ max_clients *= NFS4_CLIENTS_PER_GB;
+ nn->nfs4_max_clients = max_t(int, max_clients, NFS4_CLIENTS_PER_GB);

return 0;

diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index 847b482155ae..bbada18225b1 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -341,6 +341,8 @@ void nfsd_lockd_shutdown(void);

Protected by #ifdef CONFIG_NFSD_V4:

#define NFSD_LAUNDROMAT_MINTIMEOUT 1 /* seconds */
#define NFSD_COURTESY_CLIENT_TIMEOUT (24 * 60 * 60) /* seconds */
+#define NFS4_CLIENTS_PER_GB 1024

* The following attributes are currently not supported by the NFSv4 server:



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds