[PATCH] NFS: Reduce stack use in encode_exchange_id()

[PATCH] NFS: Reduce stack use in encode_exchange_id()

[Jim Rees]

For comment only. I have not tested this.

encode_exchange_id() uses more stack space than necessary, giving a compile
time warning. Reduce the size of the static buffer for implementation name.

Signed-off-by: Jim Rees <rees@umich.edu>
---
 fs/nfs/nfs4xdr.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 8dba6bd..ccd1dde 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -1700,12 +1700,15 @@ static void encode_bind_conn_to_session(struct xdr_stream *xdr,
 	*p = 0;	/* use_conn_in_rdma_mode = False */
 }
 
+#define IMPL_NAME_LIMIT (sizeof(utsname()->sysname) + sizeof(utsname()->release) + \
+			 sizeof(utsname()->version) + sizeof(utsname()->machine) + 8)
+
 static void encode_exchange_id(struct xdr_stream *xdr,
 			       struct nfs41_exchange_id_args *args,
 			       struct compound_hdr *hdr)
 {
 	__be32 *p;
-	char impl_name[NFS4_OPAQUE_LIMIT];
+	char impl_name[IMPL_NAME_LIMIT];
 	int len = 0;
 
 	encode_op_hdr(xdr, OP_EXCHANGE_ID, decode_exchange_id_maxsz, hdr);
@@ -1720,7 +1723,7 @@ static void encode_exchange_id(struct xdr_stream *xdr,
 	if (send_implementation_id &&
 	    sizeof(CONFIG_NFS_V4_1_IMPLEMENTATION_ID_DOMAIN) > 1 &&
 	    sizeof(CONFIG_NFS_V4_1_IMPLEMENTATION_ID_DOMAIN)
-		<= NFS4_OPAQUE_LIMIT + 1)
+		<= sizeof(impl_name) + 1)
 		len = snprintf(impl_name, sizeof(impl_name), "%s %s %s %s",
 			       utsname()->sysname, utsname()->release,
 			       utsname()->version, utsname()->machine);
-- 
1.7.9.5

Re: [PATCH] NFS: Reduce stack use in encode_exchange_id()

[Adamson, Dros]

Thanks Jim, I'll test this and report back.

-dros

On Oct 26, 2012, at 11:06 PM, "Jim Rees" <rees@umich.edu> wrote:

> For comment only. I have not tested this.
> 
> encode_exchange_id() uses more stack space than necessary, giving a compile
> time warning. Reduce the size of the static buffer for implementation name.
> 
> Signed-off-by: Jim Rees <rees@umich.edu>
> ---
> fs/nfs/nfs4xdr.c |    7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index 8dba6bd..ccd1dde 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -1700,12 +1700,15 @@ static void encode_bind_conn_to_session(struct xdr_stream *xdr,
>    *p = 0;    /* use_conn_in_rdma_mode = False */
> }
> 
> +#define IMPL_NAME_LIMIT (sizeof(utsname()->sysname) + sizeof(utsname()->release) + \
> +             sizeof(utsname()->version) + sizeof(utsname()->machine) + 8)
> +
> static void encode_exchange_id(struct xdr_stream *xdr,
>                   struct nfs41_exchange_id_args *args,
>                   struct compound_hdr *hdr)
> {
>    __be32 *p;
> -    char impl_name[NFS4_OPAQUE_LIMIT];
> +    char impl_name[IMPL_NAME_LIMIT];
>    int len = 0;
> 
>    encode_op_hdr(xdr, OP_EXCHANGE_ID, decode_exchange_id_maxsz, hdr);
> @@ -1720,7 +1723,7 @@ static void encode_exchange_id(struct xdr_stream *xdr,
>    if (send_implementation_id &&
>        sizeof(CONFIG_NFS_V4_1_IMPLEMENTATION_ID_DOMAIN) > 1 &&
>        sizeof(CONFIG_NFS_V4_1_IMPLEMENTATION_ID_DOMAIN)
> -        <= NFS4_OPAQUE_LIMIT + 1)
> +        <= sizeof(impl_name) + 1)
>        len = snprintf(impl_name, sizeof(impl_name), "%s %s %s %s",
>                   utsname()->sysname, utsname()->release,
>                   utsname()->version, utsname()->machine);
> -- 
> 1.7.9.5
> 
> --
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[PATCH] NFS: Reduce stack use in encode_exchange_id()

[Jim Rees]

encode_exchange_id() uses more stack space than necessary, giving a compile
time warning. Reduce the size of the static buffer for implementation name.

Signed-off-by: Jim Rees <rees@umich.edu>
Reviewed-by: "Adamson, Dros" <Weston.Adamson@netapp.com>
---
 fs/nfs/nfs4xdr.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 672d9b0..e9c101d 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -1706,12 +1706,15 @@ static void encode_bind_conn_to_session(struct xdr_stream *xdr,
 	*p = 0;	/* use_conn_in_rdma_mode = False */
 }
 
+#define IMPL_NAME_LIMIT (sizeof(utsname()->sysname) + sizeof(utsname()->release) + \
+			 sizeof(utsname()->version) + sizeof(utsname()->machine) + 8)
+
 static void encode_exchange_id(struct xdr_stream *xdr,
 			       struct nfs41_exchange_id_args *args,
 			       struct compound_hdr *hdr)
 {
 	__be32 *p;
-	char impl_name[NFS4_OPAQUE_LIMIT];
+	char impl_name[IMPL_NAME_LIMIT];
 	int len = 0;
 
 	encode_op_hdr(xdr, OP_EXCHANGE_ID, decode_exchange_id_maxsz, hdr);
@@ -1726,7 +1729,7 @@ static void encode_exchange_id(struct xdr_stream *xdr,
 	if (send_implementation_id &&
 	    sizeof(CONFIG_NFS_V4_1_IMPLEMENTATION_ID_DOMAIN) > 1 &&
 	    sizeof(CONFIG_NFS_V4_1_IMPLEMENTATION_ID_DOMAIN)
-		<= NFS4_OPAQUE_LIMIT + 1)
+		<= sizeof(impl_name) + 1)
 		len = snprintf(impl_name, sizeof(impl_name), "%s %s %s %s",
 			       utsname()->sysname, utsname()->release,
 			       utsname()->version, utsname()->machine);
-- 
1.7.9.5

Re: [PATCH] NFS: Reduce stack use in encode_exchange_id()

[Myklebust, Trond]

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Re: [PATCH] NFS: Reduce stack use in encode_exchange_id()

[Jim Rees]

Myklebust, Trond wrote:

  Hmm... Shouldn't we also be changing encode_exchange_id_maxsz to mirror
  this new buffer limit?

Probably. I'll fix it. Thanks.