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>

7 files changed, 63 insertions, 65 deletions

diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 2dd95ebf4935..6259a4b8579f 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -283,6 +283,16 @@ nfsd3_proc_symlink(struct svc_rqst *rqstp)
 	struct nfsd3_diropres *resp = rqstp->rq_resp;
 	__be32	nfserr;
 
+	if (argp->tlen == 0)
+		RETURN_STATUS(nfserr_inval);
+	if (argp->tlen > NFS3_MAXPATHLEN)
+		RETURN_STATUS(nfserr_nametoolong);
+
+	argp->tname = svc_fill_symlink_pathname(rqstp, &argp->first,
+						argp->tlen);
+	if (IS_ERR(argp->tname))
+		RETURN_STATUS(nfserrno(PTR_ERR(argp->tname)));
+
 	dprintk("nfsd: SYMLINK(3)  %s %.*s -> %.*s\n",
 				SVCFH_fmt(&argp->ffh),
 				argp->flen, argp->fname,
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;
 }
 
diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index 1995ea6bfd2b..f107f9fa8e15 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -449,17 +449,19 @@ nfsd_proc_symlink(struct svc_rqst *rqstp)
 	struct svc_fh	newfh;
 	__be32		nfserr;
 
+	if (argp->tlen > NFS_MAXPATHLEN)
+		return nfserr_nametoolong;
+
+	argp->tname = svc_fill_symlink_pathname(rqstp, &argp->first,
+						argp->tlen);
+	if (IS_ERR(argp->tname))
+		return nfserrno(PTR_ERR(argp->tname));
+
 	dprintk("nfsd: SYMLINK  %s %.*s -> %.*s\n",
 		SVCFH_fmt(&argp->ffh), argp->flen, argp->fname,
 		argp->tlen, argp->tname);
 
 	fh_init(&newfh, NFS_FHSIZE);
-	/*
-	 * Crazy hack: the request fits in a page, and already-decoded
-	 * attributes follow argp->tname, so it's safe to just write a
-	 * null to ensure it's null-terminated:
-	 */
-	argp->tname[argp->tlen] = '\0';
 	nfserr = nfsd_symlink(rqstp, &argp->ffh, argp->fname, argp->flen,
 						 argp->tname, &newfh);
 
diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
index db24ae8b67e0..a43e8260520a 100644
--- a/fs/nfsd/nfsxdr.c
+++ b/fs/nfsd/nfsxdr.c
@@ -71,22 +71,6 @@ decode_filename(__be32 *p, char **namp, unsigned int *lenp)
 }
 
 static __be32 *
-decode_pathname(__be32 *p, char **namp, unsigned int *lenp)
-{
-	char		*name;
-	unsigned int	i;
-
-	if ((p = xdr_decode_string_inplace(p, namp, lenp, NFS_MAXPATHLEN)) != NULL) {
-		for (i = 0, name = *namp; i < *lenp; i++, name++) {
-			if (*name == '\0')
-				return NULL;
-		}
-	}
-
-	return p;
-}
-
-static __be32 *
 decode_sattr(__be32 *p, struct iattr *iap)
 {
 	u32	tmp, tmp1;
@@ -384,14 +368,39 @@ int
 nfssvc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p)
 {
 	struct nfsd_symlinkargs *args = rqstp->rq_argp;
+	char *base = (char *)p;
+	size_t xdrlen;
 
 	if (   !(p = decode_fh(p, &args->ffh))
-	    || !(p = decode_filename(p, &args->fname, &args->flen))
-	    || !(p = decode_pathname(p, &args->tname, &args->tlen)))
+	    || !(p = decode_filename(p, &args->fname, &args->flen)))
 		return 0;
-	p = decode_sattr(p, &args->attrs);
 
-	return xdr_argsize_check(rqstp, p);
+	args->tlen = ntohl(*p++);
+	if (args->tlen == 0)
+		return 0;
+
+	args->first.iov_base = p;
+	args->first.iov_len = rqstp->rq_arg.head[0].iov_len;
+	args->first.iov_len -= (char *)p - base;
+
+	/* This request is never larger than a page. Therefore,
+	 * transport will deliver either:
+	 * 1. pathname in the pagelist -> sattr is in the tail.
+	 * 2. everything in the head buffer -> sattr is in the head.
+	 */
+	if (rqstp->rq_arg.page_len) {
+		if (args->tlen != rqstp->rq_arg.page_len)
+			return 0;
+		p = rqstp->rq_arg.tail[0].iov_base;
+	} else {
+		xdrlen = XDR_QUADLEN(args->tlen);
+		if (xdrlen > args->first.iov_len - (8 * sizeof(__be32)))
+			return 0;
+		p += xdrlen;
+	}
+	decode_sattr(p, &args->attrs);
+
+	return 1;
 }
 
 int
diff --git a/fs/nfsd/xdr.h b/fs/nfsd/xdr.h
index a765c414015e..ea7cca3a64b7 100644
--- a/fs/nfsd/xdr.h
+++ b/fs/nfsd/xdr.h
@@ -72,6 +72,7 @@ struct nfsd_symlinkargs {
 	char *			tname;
 	unsigned int		tlen;
 	struct iattr		attrs;
+	struct kvec		first;
 };
 
 struct nfsd_readdirargs {
diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h
index deccf7f691e9..2cb29e961a76 100644
--- a/fs/nfsd/xdr3.h
+++ b/fs/nfsd/xdr3.h
@@ -90,6 +90,7 @@ struct nfsd3_symlinkargs {
 	char *			tname;
 	unsigned int		tlen;
 	struct iattr		attrs;
+	struct kvec		first;
 };
 
 struct nfsd3_readdirargs {
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 7cbc129092fe..468020fe2a07 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -110,6 +110,7 @@ struct nfsd4_create {
 		struct {
 			u32 datalen;
 			char *data;
+			struct kvec first;
 		} link;   /* NF4LNK */
 		struct {
 			u32 specdata1;
@@ -124,6 +125,7 @@ struct nfsd4_create {
 };
 #define cr_datalen	u.link.datalen
 #define cr_data		u.link.data
+#define cr_first	u.link.first
 #define cr_specdata1	u.dev.specdata1
 #define cr_specdata2	u.dev.specdata2