From: Stefan Metzmacher Date: Thu, 5 Feb 2026 16:14:14 +0000 (+0100) Subject: smb: client: correct value for smbd_max_fragmented_recv_size X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4a93d1ee2d0206970b6eb13fbffe07938cd95948;p=thirdparty%2Fkernel%2Fstable.git smb: client: correct value for smbd_max_fragmented_recv_size When we download a file without rdma offload or get a large directly enumeration from the server, the server might want to send up to smbd_max_fragmented_recv_size bytes, but if it is too large all our recv buffers might already be moved to the recv_io.reassembly.list and we're no longer able to grant recv credits. The maximum fragmented upper-layer payload receive size supported Assume max_payload_per_credit is smbd_max_receive_size - 24 = 1340 The maximum number would be smbd_receive_credit_max * max_payload_per_credit 1340 * 255 = 341700 (0x536C4) The minimum value from the spec is 131072 (0x20000) For now we use the logic we used in ksmbd before: (1364 * 255) / 2 = 173910 (0x2A756) Fixes: 03bee01d6215 ("CIFS: SMBD: Add SMB Direct protocol initial values and constants") Cc: Steve French Cc: Tom Talpey Cc: Long Li Cc: Namjae Jeon Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Signed-off-by: Stefan Metzmacher Signed-off-by: Steve French --- diff --git a/fs/smb/client/smbdirect.c b/fs/smb/client/smbdirect.c index bb236f80b3c7..d44847c9d8fc 100644 --- a/fs/smb/client/smbdirect.c +++ b/fs/smb/client/smbdirect.c @@ -101,8 +101,23 @@ int smbd_send_credit_target = 255; /* The maximum single message size can be sent to remote peer */ int smbd_max_send_size = 1364; -/* The maximum fragmented upper-layer payload receive size supported */ -int smbd_max_fragmented_recv_size = 1024 * 1024; +/* + * The maximum fragmented upper-layer payload receive size supported + * + * Assume max_payload_per_credit is + * smbd_max_receive_size - 24 = 1340 + * + * The maximum number would be + * smbd_receive_credit_max * max_payload_per_credit + * + * 1340 * 255 = 341700 (0x536C4) + * + * The minimum value from the spec is 131072 (0x20000) + * + * For now we use the logic we used in ksmbd before: + * (1364 * 255) / 2 = 173910 (0x2A756) + */ +int smbd_max_fragmented_recv_size = (1364 * 255) / 2; /* The maximum single-message size which can be received */ int smbd_max_receive_size = 1364;