SUNRPC: Refactor logic to NUL-terminate strings in pages

Clean up: Introduce a helper to '\0'-terminate XDR strings
that are placed in a page in the page cache.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

5 files changed, 21 insertions, 14 deletions

diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index e15bc0306d0c..79c74387a2fe 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -596,7 +596,6 @@ nfs_xdr_readlinkres(struct rpc_rqst *req, __be32 *p, void *dummy)
         struct kvec *iov = rcvbuf->head;
         size_t hdrlen;
         u32 len, recvd;
-        char    *kaddr;
         int     status;
 
         if ((status = ntohl(*p++)))
@@ -623,10 +622,7 @@ nfs_xdr_readlinkres(struct rpc_rqst *req, __be32 *p, void *dummy)
                 return -EIO;
         }
 
-        /* NULL terminate the string we got */
-        kaddr = (char *)kmap_atomic(rcvbuf->pages[0], KM_USER0);
-        kaddr[len+rcvbuf->page_base] = '\0';
-        kunmap_atomic(kaddr, KM_USER0);
+        xdr_terminate_string(rcvbuf, len);
         return 0;
 }
 
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 89c40f8ec6e6..52b2fda66e63 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -824,7 +824,6 @@ nfs3_xdr_readlinkres(struct rpc_rqst *req, __be32 *p, struct nfs_fattr *fattr)
         struct kvec *iov = rcvbuf->head;
         size_t hdrlen;
         u32 len, recvd;
-        char    *kaddr;
         int     status;
 
         status = ntohl(*p++);
@@ -857,10 +856,7 @@ nfs3_xdr_readlinkres(struct rpc_rqst *req, __be32 *p, struct nfs_fattr *fattr)
                 return -EIO;
         }
 
-        /* NULL terminate the string we got */
-        kaddr = (char*)kmap_atomic(rcvbuf->pages[0], KM_USER0);
-        kaddr[len+rcvbuf->page_base] = '\0';
-        kunmap_atomic(kaddr, KM_USER0);
+        xdr_terminate_string(rcvbuf, len);
         return 0;
 }
 
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index b0bd7efe8100..86ab69eb149c 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4299,7 +4299,6 @@ static int decode_readlink(struct xdr_stream *xdr, struct rpc_rqst *req)
         size_t hdrlen;
         u32 len, recvd;
         __be32 *p;
-        char *kaddr;
         int status;
 
         status = decode_op_hdr(xdr, OP_READLINK);
@@ -4330,9 +4329,7 @@ static int decode_readlink(struct xdr_stream *xdr, struct rpc_rqst *req)
          * and and null-terminate the text (the VFS expects
          * null-termination).
          */
-        kaddr = (char *)kmap_atomic(rcvbuf->pages[0], KM_USER0);
-        kaddr[len+rcvbuf->page_base] = '\0';
-        kunmap_atomic(kaddr, KM_USER0);
+        xdr_terminate_string(rcvbuf, len);
         return 0;
 out_overflow:
         print_overflow_msg(__func__, xdr);
diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index 35cf2e8cd7c6..8c1dcbb54d89 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -108,6 +108,7 @@ void	xdr_encode_pages(struct xdr_buf *, struct page **, unsigned int,
                          unsigned int);
 void    xdr_inline_pages(struct xdr_buf *, unsigned int,
                          struct page **, unsigned int, unsigned int);
+void    xdr_terminate_string(struct xdr_buf *, const u32);
 
 static inline __be32 *xdr_encode_array(__be32 *p, const void *s, unsigned int len)
 {
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 3bbef7f5f826..e0725d9d8107 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -111,6 +111,23 @@ xdr_decode_string_inplace(__be32 *p, char **sp,
 }
 EXPORT_SYMBOL_GPL(xdr_decode_string_inplace);
 
+/**
+ * xdr_terminate_string - '\0'-terminate a string residing in an xdr_buf
+ * @buf: XDR buffer where string resides
+ * @len: length of string, in bytes
+ *
+ */
+void
+xdr_terminate_string(struct xdr_buf *buf, const u32 len)
+{
+        char *kaddr;
+
+        kaddr = kmap_atomic(buf->pages[0], KM_USER0);
+        kaddr[buf->page_base + len] = '\0';
+        kunmap_atomic(kaddr, KM_USER0);
+}
+EXPORT_SYMBOL(xdr_terminate_string);
+
 void
 xdr_encode_pages(struct xdr_buf *xdr, struct page **pages, unsigned int base,
                  unsigned int len)