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Commit 082d4bd7 authored by J. Bruce Fields's avatar J. Bruce Fields
Browse files

nfsd4: "backfill" using write_bytes_to_xdr_buf 



Normally xdr encoding proceeds in a single pass from start of a buffer
to end, but sometimes we have to write a few bytes to an earlier
position.

Use write_bytes_to_xdr_buf for these cases rather than saving a pointer
to write to.  We plan to rewrite xdr_reserve_space to handle encoding
across page boundaries using a scratch buffer, and don't want to risk
writing to a pointer that was contained in a scratch buffer.

Also it will no longer be safe to calculate lengths by subtracting two
pointers, so use xdr_buf offsets instead.

Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 1fcea5b2

fs/nfsd/nfs4xdr.c

+26 −19
Original line number Diff line number Diff line
@@ -1759,16 +1759,19 @@ static __be32 nfsd4_encode_components_esc(struct xdr_stream *xdr, char sep, 
					  char esc_exit)

{

	__be32 *p;

	__be32 *countp;

	__be32 pathlen;

	int pathlen_offset;

	int strlen, count=0;

	char *str, *end, *next;



	dprintk("nfsd4_encode_components(%s)\n", components);



	pathlen_offset = xdr->buf->len;

	p = xdr_reserve_space(xdr, 4);

	if (!p)

		return nfserr_resource;

	countp = p;

	WRITE32(0); /* We will fill this in with @count later */

	p++; /* We will fill this in with @count later */



	end = str = components;

	while (*end) {

		bool found_esc = false;
@@ -1801,8 +1804,8 @@ static __be32 nfsd4_encode_components_esc(struct xdr_stream *xdr, char sep, 
			end++;

		str = end;

	}

	p = countp;

	WRITE32(count);

	pathlen = htonl(xdr->buf->len - pathlen_offset);

	write_bytes_to_xdr_buf(xdr->buf, pathlen_offset, &pathlen, 4);

	return 0;

}
@@ -2054,7 +2057,8 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp, 
	struct kstatfs statfs;

	__be32 *p;

	int starting_len = xdr->buf->len;

	__be32 *attrlenp;

	int attrlen_offset;

	__be32 attrlen;

	u32 dummy;

	u64 dummy64;

	u32 rdattr_err = 0;
@@ -2159,10 +2163,12 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp, 
		WRITE32(1);

		WRITE32(bmval0);

	}



	attrlen_offset = xdr->buf->len;

	p = xdr_reserve_space(xdr, 4);

	if (!p)

		goto out_resource;

	attrlenp = p++;                /* to be backfilled later */

	p++;                /* to be backfilled later */



	if (bmval0 & FATTR4_WORD0_SUPPORTED_ATTRS) {

		u32 word0 = nfsd_suppattrs0(minorversion);
@@ -2534,7 +2540,8 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp, 
		WRITE32(NFSD_SUPPATTR_EXCLCREAT_WORD2);

	}



	*attrlenp = htonl((char *)xdr->p - (char *)attrlenp - 4);

	attrlen = htonl(xdr->buf->len - attrlen_offset - 4);

	write_bytes_to_xdr_buf(xdr->buf, attrlen_offset, &attrlen, 4);

	status = nfs_ok;



out:
@@ -3664,15 +3671,16 @@ __be32 nfsd4_check_resp_size(struct nfsd4_compoundres *resp, u32 pad) 
void

nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)

{

	struct xdr_stream *xdr = &resp->xdr;

	struct nfs4_stateowner *so = resp->cstate.replay_owner;

	struct svc_rqst *rqstp = resp->rqstp;

	__be32 *statp;

	int post_err_offset;

	nfsd4_enc encoder;

	__be32 *p;



	RESERVE_SPACE(8);

	WRITE32(op->opnum);

	statp = p++;	/* to be backfilled at the end */

	post_err_offset = xdr->buf->len;



	if (op->opnum == OP_ILLEGAL)

		goto status;
@@ -3698,20 +3706,19 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op) 
		 * bug if we had to do this on a non-idempotent op:

		 */

		warn_on_nonidempotent_op(op);

		resp->xdr.p = statp + 1;

		xdr_truncate_encode(xdr, post_err_offset);

	}

	if (so) {

		int len = xdr->buf->len - post_err_offset;



		so->so_replay.rp_status = op->status;

		so->so_replay.rp_buflen = (char *)resp->xdr.p

						- (char *)(statp+1);

		memcpy(so->so_replay.rp_buf, statp+1, so->so_replay.rp_buflen);

		so->so_replay.rp_buflen = len;

		read_bytes_from_xdr_buf(xdr->buf, post_err_offset,

						so->so_replay.rp_buf, len);

	}

status:

	/*

	 * Note: We write the status directly, instead of using WRITE32(),

	 * since it is already in network byte order.

	 */

	*statp = op->status;

	/* Note that op->status is already in network byte order: */

	write_bytes_to_xdr_buf(xdr->buf, post_err_offset - 4, &op->status, 4);

}



/*