[PATCH v2] ksmbd: reduce smb direct max read/write size

[PATCH v2] ksmbd: reduce smb direct max read/write size

[Namjae Jeon]

ksmbd does not support more than one Buffer Descriptor V1 element in
an smbdirect protocol request. Reducing the maximum read/write size to
about 512KB allows interoperability with Windows over a wider variety
of RDMA NICs, as an interim workaround.

Cc: Tom Talpey <tom@talpey.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 v2:
   - update patch description (Written by Tom Talpey).

 fs/ksmbd/transport_rdma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ksmbd/transport_rdma.c b/fs/ksmbd/transport_rdma.c
index 3c1ec1ac0b27..ba5a22bc2e6d 100644
--- a/fs/ksmbd/transport_rdma.c
+++ b/fs/ksmbd/transport_rdma.c
@@ -80,7 +80,7 @@ static int smb_direct_max_fragmented_recv_size = 1024 * 1024;
 /*  The maximum single-message size which can be received */
 static int smb_direct_max_receive_size = 8192;
 
-static int smb_direct_max_read_write_size = 1048512;
+static int smb_direct_max_read_write_size = 524224;
 
 static int smb_direct_max_outstanding_rw_ops = 8;
 
-- 
2.25.1

Re: [PATCH v2] ksmbd: reduce smb direct max read/write size

[Tom Talpey]

Thanks for walking me through the explanation.

Reviewed-By: Tom Talpey <tom@talpey.com>

Feb 1, 2022 4:16:59 AM Namjae Jeon <linkinjeon@kernel.org>:

> ksmbd does not support more than one Buffer Descriptor V1 element in
> an smbdirect protocol request. Reducing the maximum read/write size to
> about 512KB allows interoperability with Windows over a wider variety
> of RDMA NICs, as an interim workaround.
> 
> Cc: Tom Talpey <tom@talpey.com>
> Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
> ---
> v2:
>    - update patch description (Written by Tom Talpey).
> 
> fs/ksmbd/transport_rdma.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ksmbd/transport_rdma.c b/fs/ksmbd/transport_rdma.c
> index 3c1ec1ac0b27..ba5a22bc2e6d 100644
> --- a/fs/ksmbd/transport_rdma.c
> +++ b/fs/ksmbd/transport_rdma.c
> @@ -80,7 +80,7 @@ static int smb_direct_max_fragmented_recv_size = 1024 * 1024;
> /*  The maximum single-message size which can be received */
> static int smb_direct_max_receive_size = 8192;
> 
> -static int smb_direct_max_read_write_size = 1048512;
> +static int smb_direct_max_read_write_size = 524224;
> 
> static int smb_direct_max_outstanding_rw_ops = 8;
> 
> -- 
> 2.25.1