NFSD: Clean up legacy NFS SYMLINK argument XDR decoders

Move common code in NFSD's legacy SYMLINK decoders into a helper.
The immediate benefits include:

 - one fewer data copies on transports that support DDP
 - consistent error checking across all versions
 - reduction of code duplication
 - support for both legal forms of SYMLINK requests on RDMA
   transports for all versions of NFS (in particular, NFSv2, for
   completeness)

In the long term, this helper is an appropriate spot to perform a
per-transport call-out to fill the pathname argument using, say,
RDMA Reads.

Filling the pathname in the proc function also means that eventually
the incoming filehandle can be interpreted so that filesystem-
specific memory can be allocated as a sink for the pathname
argument, rather than using anonymous pages.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 12 insertions, 39 deletions

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index e19fc5d8bcb5..3192b544a441 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -481,51 +481,24 @@ int
 nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p)
 {
 	struct nfsd3_symlinkargs *args = rqstp->rq_argp;
-	unsigned int len, avail;
-	char *old, *new;
-	struct kvec *vec;
+	char *base = (char *)p;
+	size_t dlen;
 
 	if (!(p = decode_fh(p, &args->ffh)) ||
-	    !(p = decode_filename(p, &args->fname, &args->flen))
-		)
+	    !(p = decode_filename(p, &args->fname, &args->flen)))
 		return 0;
 	p = decode_sattr3(p, &args->attrs);
 
-	/* now decode the pathname, which might be larger than the first page.
-	 * As we have to check for nul's anyway, we copy it into a new page
-	 * This page appears in the rq_res.pages list, but as pages_len is always
-	 * 0, it won't get in the way
-	 */
-	len = ntohl(*p++);
-	if (len == 0 || len > NFS3_MAXPATHLEN || len >= PAGE_SIZE)
-		return 0;
-	args->tname = new = page_address(*(rqstp->rq_next_page++));
-	args->tlen = len;
-	/* first copy and check from the first page */
-	old = (char*)p;
-	vec = &rqstp->rq_arg.head[0];
-	if ((void *)old > vec->iov_base + vec->iov_len)
-		return 0;
-	avail = vec->iov_len - (old - (char*)vec->iov_base);
-	while (len && avail && *old) {
-		*new++ = *old++;
-		len--;
-		avail--;
-	}
-	/* now copy next page if there is one */
-	if (len && !avail && rqstp->rq_arg.page_len) {
-		avail = min_t(unsigned int, rqstp->rq_arg.page_len, PAGE_SIZE);
-		old = page_address(rqstp->rq_arg.pages[0]);
-	}
-	while (len && avail && *old) {
-		*new++ = *old++;
-		len--;
-		avail--;
-	}
-	*new = '\0';
-	if (len)
-		return 0;
+	args->tlen = ntohl(*p++);
 
+	args->first.iov_base = p;
+	args->first.iov_len = rqstp->rq_arg.head[0].iov_len;
+	args->first.iov_len -= (char *)p - base;
+
+	dlen = args->first.iov_len + rqstp->rq_arg.page_len +
+	       rqstp->rq_arg.tail[0].iov_len;
+	if (dlen < XDR_QUADLEN(args->tlen) << 2)
+		return 0;
 	return 1;
 }