[PATCH v5 19/19] SUNRPC: Bump the maximum payload size for the server

cel
2025-05-09T19:04:13Z

Increase the maximum server-side RPC payload to 4MB. The default
remains at 1MB.

An API to adjust the operational maximum was added in 2006 by commit
596bbe53eb3a ("[PATCH] knfsd: Allow max size of NFSd payload to be
configured"). To adjust the operational maximum using this API, shut
down the NFS server. Then echo a new value into:

/proc/fs/nfsd/max_block_size

And restart the NFS server.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
include/linux/sunrpc/svc.h | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index d57df042e24a..48666b83fe68 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -119,14 +119,14 @@ void svc_destroy(struct svc_serv **svcp);
* Linux limit; someone who cares more about NFS/UDP performance
* can test a larger number.
*
- * For TCP transports we have more freedom. A size of 1MB is
- * chosen to match the client limit. Other OSes are known to
- * have larger limits, but those numbers are probably beyond
- * the point of diminishing returns.
+ * For non-UDP transports we have more freedom. A size of 4MB is
+ * chosen to accommodate clients that support larger I/O sizes.
*/
-#define RPCSVC_MAXPAYLOAD (1*1024*1024u)
-#define RPCSVC_MAXPAYLOAD_TCP RPCSVC_MAXPAYLOAD
-#define RPCSVC_MAXPAYLOAD_UDP (32*1024u)
+enum {
+ RPCSVC_MAXPAYLOAD = 4 * 1024 * 1024,
+ RPCSVC_MAXPAYLOAD_TCP = RPCSVC_MAXPAYLOAD,
+ RPCSVC_MAXPAYLOAD_UDP = 32 * 1024,
+};

extern u32 svc_max_payload(const struct svc_rqst *rqstp);

--
2.49.0