nfsd4: allow encoding across page boundaries

After this we can handle for example getattr of very large ACLs.

Read, readdir, readlink are still special cases with their own limits.

Also we can't handle a new operation starting close to the end of a
page.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 43 insertions, 17 deletions

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index bd529e523087..d3a576dbd99b 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1624,6 +1624,7 @@ static int nfsd4_max_reply(u32 opnum)
 		 * the head and tail in another page:
 		 */
 		return 2 * PAGE_SIZE;
+	case OP_GETATTR:
 	case OP_READ:
 		return INT_MAX;
 	default:
@@ -2560,21 +2561,31 @@ out_resource:
 	goto out;
 }
 
+static void svcxdr_init_encode_from_buffer(struct xdr_stream *xdr,
+				struct xdr_buf *buf, __be32 *p, int bytes)
+{
+	xdr->scratch.iov_len = 0;
+	memset(buf, 0, sizeof(struct xdr_buf));
+	buf->head[0].iov_base = p;
+	buf->head[0].iov_len = 0;
+	buf->len = 0;
+	xdr->buf = buf;
+	xdr->iov = buf->head;
+	xdr->p = p;
+	xdr->end = (void *)p + bytes;
+	buf->buflen = bytes;
+}
+
 __be32 nfsd4_encode_fattr_to_buf(__be32 **p, int words,
 			struct svc_fh *fhp, struct svc_export *exp,
 			struct dentry *dentry, u32 *bmval,
 			struct svc_rqst *rqstp, int ignore_crossmnt)
 {
-	struct xdr_buf dummy = {
-			.head[0] = {
-				.iov_base = *p,
-			},
-			.buflen = words << 2,
-		};
+	struct xdr_buf dummy;
 	struct xdr_stream xdr;
 	__be32 ret;
 
-	xdr_init_encode(&xdr, &dummy, NULL);
+	svcxdr_init_encode_from_buffer(&xdr, &dummy, *p, words << 2);
 	ret = nfsd4_encode_fattr(&xdr, fhp, exp, dentry, bmval, rqstp,
 							ignore_crossmnt);
 	*p = xdr.p;
@@ -3064,8 +3075,6 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 
 	if (nfserr)
 		return nfserr;
-	if (resp->xdr.buf->page_len)
-		return nfserr_resource;
 
 	p = xdr_reserve_space(xdr, 8); /* eof flag and byte count */
 	if (!p)
@@ -3075,6 +3084,9 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 	if (xdr->end - xdr->p < 1)
 		return nfserr_resource;
 
+	if (resp->xdr.buf->page_len)
+		return nfserr_resource;
+
 	maxcount = svc_max_payload(resp->rqstp);
 	if (maxcount > read->rd_length)
 		maxcount = read->rd_length;
@@ -3119,6 +3131,8 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 				- (char *)resp->xdr.buf->head[0].iov_base);
 	resp->xdr.buf->page_len = maxcount;
 	xdr->buf->len += maxcount;
+	xdr->page_ptr += v;
+	xdr->buf->buflen = maxcount + PAGE_SIZE - 2 * RPC_MAX_AUTH_SIZE;
 	xdr->iov = xdr->buf->tail;
 
 	/* Use rest of head for padding and remaining ops: */
@@ -3145,6 +3159,11 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
 
 	if (nfserr)
 		return nfserr;
+
+	p = xdr_reserve_space(xdr, 4);
+	if (!p)
+		return nfserr_resource;
+
 	if (resp->xdr.buf->page_len)
 		return nfserr_resource;
 	if (!*resp->rqstp->rq_next_page)
@@ -3154,10 +3173,6 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
 
 	maxcount = PAGE_SIZE;
 
-	p = xdr_reserve_space(xdr, 4);
-	if (!p)
-		return nfserr_resource;
-
 	if (xdr->end - xdr->p < 1)
 		return nfserr_resource;
 
@@ -3180,6 +3195,8 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
 				- (char *)resp->xdr.buf->head[0].iov_base;
 	resp->xdr.buf->page_len = maxcount;
 	xdr->buf->len += maxcount;
+	xdr->page_ptr += 1;
+	xdr->buf->buflen -= PAGE_SIZE;
 	xdr->iov = xdr->buf->tail;
 
 	/* Use rest of head for padding and remaining ops: */
@@ -3206,15 +3223,16 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4
 
 	if (nfserr)
 		return nfserr;
-	if (resp->xdr.buf->page_len)
-		return nfserr_resource;
-	if (!*resp->rqstp->rq_next_page)
-		return nfserr_resource;
 
 	p = xdr_reserve_space(xdr, NFS4_VERIFIER_SIZE);
 	if (!p)
 		return nfserr_resource;
 
+	if (resp->xdr.buf->page_len)
+		return nfserr_resource;
+	if (!*resp->rqstp->rq_next_page)
+		return nfserr_resource;
+
 	/* XXX: Following NFSv3, we ignore the READDIR verifier for now. */
 	WRITE32(0);
 	WRITE32(0);
@@ -3266,6 +3284,10 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4
 
 	xdr->iov = xdr->buf->tail;
 
+	xdr->page_ptr++;
+	xdr->buf->buflen -= PAGE_SIZE;
+	xdr->iov = xdr->buf->tail;
+
 	/* Use rest of head for padding and remaining ops: */
 	resp->xdr.buf->tail[0].iov_base = tailbase;
 	resp->xdr.buf->tail[0].iov_len = 0;
@@ -3800,6 +3822,8 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
 	       !nfsd4_enc_ops[op->opnum]);
 	encoder = nfsd4_enc_ops[op->opnum];
 	op->status = encoder(resp, op->status, &op->u);
+	xdr_commit_encode(xdr);
+
 	/* nfsd4_check_resp_size guarantees enough room for error status */
 	if (!op->status) {
 		int space_needed = 0;
@@ -3919,6 +3943,8 @@ nfs4svc_encode_compoundres(struct svc_rqst *rqstp, __be32 *p, struct nfsd4_compo
 	WARN_ON_ONCE(buf->len != buf->head[0].iov_len + buf->page_len +
 				 buf->tail[0].iov_len);
 
+	rqstp->rq_next_page = resp->xdr.page_ptr + 1;
+
 	p = resp->tagp;
 	*p++ = htonl(resp->taglen);
 	memcpy(p, resp->tag, resp->taglen);