[PATCH] kNFSd - 2 of 2 - Change NFSv4 reply encoding to cope with multiple pages.

This allows NFSv4 responses to cover move than one page.  There are
still limits though.  There can be at most one 'data' response which
includes READ, READLINK, READDIR.  For these responses, the interesting
data goes in a separate page or, for READ, list of pages.

All responses before the 'data' response must fit in one page, and all
responses after it must also fit in one (separate) page.

fs/nfsd/nfs4proc.c

@@ -566,11 +566,14 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
 	fh_init(&current_fh, NFS4_FHSIZE);
 	fh_init(&save_fh, NFS4_FHSIZE);
 
-	resp->p = rqstp->rq_resbuf.buf + 3 + XDR_QUADLEN(args->taglen);
-	resp->end = rqstp->rq_resbuf.base + rqstp->rq_resbuf.buflen;
+	resp->xbuf = &rqstp->rq_res;
+	resp->p = rqstp->rq_res.head[0].iov_base + rqstp->rq_res.head[0].iov_len;
+	resp->p += 3 + XDR_QUADLEN(args->taglen);
+	resp->end = rqstp->rq_res.head[0].iov_base + PAGE_SIZE;
 	resp->taglen = args->taglen;
 	resp->tag = args->tag;
 	resp->opcnt = 0;
+	resp->rqstp = rqstp;
 
 	/*
 	 * According to RFC3010, this takes precedence over all other errors.
@@ -596,6 +599,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
 		 * failed response to the next operation.  If we don't
 		 * have enough room, fail with ERR_RESOURCE.
 		 */
+/* FIXME - is slack_space *really* words, or bytes??? - neilb */
 		slack_space = (char *)resp->end - (char *)resp->p;
 		if (slack_space < COMPOUND_SLACK_SPACE + COMPOUND_ERR_SLACK_SPACE) {
 			BUG_ON(slack_space < COMPOUND_ERR_SLACK_SPACE);

fs/nfsd/nfs4xdr.c

@@ -1689,27 +1689,52 @@ static int
 nfsd4_encode_read(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_read *read)
 {
 	u32 eof;
-	unsigned long maxcount;
+	int v, pn;
+	unsigned long maxcount, len;
 	ENCODE_HEAD;
 
 	if (nfserr)
 		return nfserr;
+	if (resp->xbuf->page_len)
+		return nfserr_resource;
 
-	maxcount = (char *)resp->end - (char *)resp->p - COMPOUND_ERR_SLACK_SPACE - 8;
+	RESERVE_SPACE(8); /* eof flag and byte count */
+
+	maxcount = NFSSVC_MAXBLKSIZE;
 	if (maxcount > read->rd_length)
 		maxcount = read->rd_length;
-	RESERVE_SPACE(maxcount + 8);
+
+	len = maxcount;
+	v = 0;
+	while (len > 0) {
+		pn = resp->rqstp->rq_resused;
+		svc_take_page(resp->rqstp);
+		read->rd_iov[v].iov_base = page_address(resp->rqstp->rq_respages[pn]);
+		read->rd_iov[v].iov_len = len < PAGE_SIZE ? len : PAGE_SIZE;
+		v++;
+		len -= PAGE_SIZE;
+	}
+	read->rd_vlen = v;
 
 	nfserr = nfsd_read(read->rd_rqstp, read->rd_fhp,
-			   read->rd_offset, (char *)p + 8, &maxcount);
+			   read->rd_offset,
+			   read->rd_iov, read->rd_vlen,
+			   &maxcount);
 	if (nfserr)
 		return nfserr;
 	eof = (read->rd_offset + maxcount >= read->rd_fhp->fh_dentry->d_inode->i_size);
 
 	WRITE32(eof);
 	WRITE32(maxcount);
-	p += XDR_QUADLEN(maxcount);
 	ADJUST_ARGS();
+	resp->xbuf->head[0].iov_len = ((char*)resp->p) - (char*)resp->xbuf->head[0].iov_base;
+	resp->p = resp->xbuf->tail[0].iov_base;
+	resp->xbuf->page_len = maxcount;
+	if (maxcount&3) {
+		*(resp->p)++ = 0;
+		resp->xbuf->tail[0].iov_base += maxcount&3;
+		resp->xbuf->tail[0].iov_len = 4 - (maxcount&3);
+	}
 	return 0;
 }
 
@@ -1717,13 +1742,24 @@ static int
 nfsd4_encode_readlink(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_readlink *readlink)
 {
 	int maxcount;
+	char *page;
 	ENCODE_HEAD;
 
 	if (nfserr)
 		return nfserr;
+	if (resp->xbuf->page_len)
+		return nfserr_resource;
 
-	maxcount = (char *)resp->end - (char *)resp->p - COMPOUND_ERR_SLACK_SPACE - 4;
-	RESERVE_SPACE(maxcount + 4);
+	svc_take_page(resp->rqstp);
+	page = page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
+
+	svc_take_page(resp->rqstp);
+	resp->xbuf->tail[0].iov_base = 
+		page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
+	resp->xbuf->tail[0].iov_len = 0;
+
+	maxcount = PAGE_SIZE;
+	RESERVE_SPACE(4);
 
 	/*
 	 * XXX: By default, the ->readlink() VFS op will truncate symlinks
@@ -1731,13 +1767,20 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_r
 	 * not, one easy fix is: if ->readlink() precisely fills the buffer,
 	 * assume that truncation occured, and return NFS4ERR_RESOURCE.
 	 */
-	nfserr = nfsd_readlink(readlink->rl_rqstp, readlink->rl_fhp, (char *)p + 4, &maxcount);
+	nfserr = nfsd_readlink(readlink->rl_rqstp, readlink->rl_fhp, page, &maxcount);
 	if (nfserr)
 		return nfserr;
 
 	WRITE32(maxcount);
-	p += XDR_QUADLEN(maxcount);
 	ADJUST_ARGS();
+	resp->xbuf->head[0].iov_len = ((char*)resp->p) - (char*)resp->xbuf->head[0].iov_base;
+	resp->p = resp->xbuf->tail[0].iov_base;
+	resp->xbuf->page_len = maxcount;
+	if (maxcount&3) {
+		*(resp->p)++ = 0;
+		resp->xbuf->tail[0].iov_base += maxcount&3;
+		resp->xbuf->tail[0].iov_len = 4 - (maxcount&3);
+	}
 	return 0;
 }
 
@@ -1746,14 +1789,22 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_re
 {
 	int maxcount;
 	loff_t offset;
+	u32 *page;
 	ENCODE_HEAD;
 
 	if (nfserr)
 		return nfserr;
+	if (resp->xbuf->page_len)
+		return nfserr_resource;
 
-	RESERVE_SPACE(16);
+	RESERVE_SPACE(8);  /* verifier */
+
+	/* XXX: Following NFSv3, we ignore the READDIR verifier for now. */
+	WRITE32(0);
+	WRITE32(0);
+	ADJUST_ARGS();
 
-	maxcount = (char *)resp->end - (char *)p - COMPOUND_ERR_SLACK_SPACE;
+	maxcount = PAGE_SIZE;
 	if (maxcount > readdir->rd_maxcount)
 		maxcount = readdir->rd_maxcount;
 
@@ -1766,13 +1817,11 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_re
 	if (maxcount < 0)
 		return nfserr_readdir_nospc;
 
-	/* XXX: Following NFSv3, we ignore the READDIR verifier for now. */
-	WRITE32(0);
-	WRITE32(0);
-
+	svc_take_page(resp->rqstp);
+	page = page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
 	readdir->common.err = 0;
 	readdir->buflen = maxcount;
-	readdir->buffer = p;
+	readdir->buffer = page;
 	readdir->offset = NULL;
 
 	offset = readdir->rd_cookie;
@@ -1781,7 +1830,7 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_re
 			      &readdir->common, nfsd4_encode_dirent);
 	if (nfserr == nfs_ok &&
 	    readdir->common.err == nfserr_readdir_nospc &&
-	    readdir->buffer == p)
+	    readdir->buffer == page) 
 		nfserr = nfserr_readdir_nospc;
 	if (!nfserr) {
 		if (readdir->offset)
@@ -1790,7 +1839,7 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_re
 		p = readdir->buffer;
 		*p++ = 0;	/* no more entries */
 		*p++ = htonl(readdir->common.err == nfserr_eof);
-		ADJUST_ARGS();
+		resp->xbuf->page_len = ((char*)p) - (char*)page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
 	}
 	return nfserr;
 }
@@ -1971,17 +2020,6 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
  * END OF "GENERIC" ENCODE ROUTINES.
  */
 
-static inline int
-xdr_ressize_check(struct svc_rqst *rqstp, u32 *p)
-{
-	struct svc_buf	*buf = &rqstp->rq_resbuf;
-
-	buf->len = p - buf->base;
-	dprintk("nfsd: ressize_check p %p base %p len %d\n",
-			p, buf->base, buf->buflen);
-	return (buf->len <= buf->buflen);
-}
-
 int
 nfs4svc_encode_voidres(struct svc_rqst *rqstp, u32 *p, void *dummy)
 {
@@ -1996,7 +2034,7 @@ nfs4svc_decode_compoundargs(struct svc_rqst *rqstp, u32 *p, struct nfsd4_compoun
 	args->p = p;
 	args->end = rqstp->rq_arg.head[0].iov_base + rqstp->rq_arg.head[0].iov_len;
 	args->pagelist = rqstp->rq_arg.pages;
-	args->pagelen = rqstp->rq_args.page_len;
+	args->pagelen = rqstp->rq_arg.page_len;
 	args->tmpp = NULL;
 	args->to_free = NULL;
 	args->ops = args->iops;
@@ -2027,12 +2065,18 @@ nfs4svc_encode_compoundres(struct svc_rqst *rqstp, u32 *p, struct nfsd4_compound
 	/*
 	 * All that remains is to write the tag and operation count...
 	 */
+	struct iovec *iov;
 	*p++ = htonl(resp->taglen);
 	memcpy(p, resp->tag, resp->taglen);
 	p += XDR_QUADLEN(resp->taglen);
 	*p++ = htonl(resp->opcnt);
 
-	BUG_ON(!xdr_ressize_check(rqstp, resp->p));
+	if (rqstp->rq_res.page_len) 
+		iov = &rqstp->rq_res.tail[0];
+	else
+		iov = &rqstp->rq_res.head[0];
+	iov->iov_len = ((char*)resp->p) - (char*)iov->iov_base;
+	BUG_ON(iov->iov_len > PAGE_SIZE);
 	return 1;
 }
 

include/linux/nfsd/xdr4.h

@@ -173,6 +173,9 @@ struct nfsd4_read {
 	stateid_t	rd_stateid;         /* request */
 	u64		rd_offset;          /* request */
 	u32		rd_length;          /* request */
+	struct iovec	rd_iov[RPCSVC_MAXPAGES];
+	int		rd_vlen;
+	
 	struct svc_rqst *rd_rqstp;          /* response */
 	struct svc_fh * rd_fhp;             /* response */
 };
@@ -311,6 +314,8 @@ struct nfsd4_compoundres {
 	/* scratch variables for XDR encode */
 	u32 *				p;
 	u32 *				end;
+	struct xdr_buf *		xbuf;
+	struct svc_rqst *		rqstp;
 
 	u32				taglen;
 	char *				tag;