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: J. Bruce Fields <bfields@redhat.com>
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@ -1759,16 +1759,19 @@ static __be32 nfsd4_encode_components_esc(struct xdr_stream *xdr, char sep,
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char esc_exit)
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{
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__be32 *p;
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__be32 *countp;
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__be32 pathlen;
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int pathlen_offset;
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int strlen, count=0;
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char *str, *end, *next;
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dprintk("nfsd4_encode_components(%s)\n", components);
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pathlen_offset = xdr->buf->len;
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p = xdr_reserve_space(xdr, 4);
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if (!p)
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return nfserr_resource;
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countp = p;
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WRITE32(0); /* We will fill this in with @count later */
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p++; /* We will fill this in with @count later */
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end = str = components;
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while (*end) {
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bool found_esc = false;
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@ -1801,8 +1804,8 @@ static __be32 nfsd4_encode_components_esc(struct xdr_stream *xdr, char sep,
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end++;
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str = end;
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}
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p = countp;
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WRITE32(count);
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pathlen = htonl(xdr->buf->len - pathlen_offset);
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write_bytes_to_xdr_buf(xdr->buf, pathlen_offset, &pathlen, 4);
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return 0;
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}
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@ -2054,7 +2057,8 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
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struct kstatfs statfs;
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__be32 *p;
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int starting_len = xdr->buf->len;
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__be32 *attrlenp;
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int attrlen_offset;
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__be32 attrlen;
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u32 dummy;
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u64 dummy64;
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u32 rdattr_err = 0;
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@ -2159,10 +2163,12 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
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WRITE32(1);
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WRITE32(bmval0);
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}
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attrlen_offset = xdr->buf->len;
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p = xdr_reserve_space(xdr, 4);
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if (!p)
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goto out_resource;
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attrlenp = p++; /* to be backfilled later */
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p++; /* to be backfilled later */
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if (bmval0 & FATTR4_WORD0_SUPPORTED_ATTRS) {
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u32 word0 = nfsd_suppattrs0(minorversion);
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@ -2534,7 +2540,8 @@ out_acl:
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WRITE32(NFSD_SUPPATTR_EXCLCREAT_WORD2);
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}
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*attrlenp = htonl((char *)xdr->p - (char *)attrlenp - 4);
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attrlen = htonl(xdr->buf->len - attrlen_offset - 4);
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write_bytes_to_xdr_buf(xdr->buf, attrlen_offset, &attrlen, 4);
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status = nfs_ok;
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out:
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@ -3664,15 +3671,16 @@ __be32 nfsd4_check_resp_size(struct nfsd4_compoundres *resp, u32 pad)
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void
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nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
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{
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struct xdr_stream *xdr = &resp->xdr;
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struct nfs4_stateowner *so = resp->cstate.replay_owner;
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struct svc_rqst *rqstp = resp->rqstp;
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__be32 *statp;
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int post_err_offset;
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nfsd4_enc encoder;
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__be32 *p;
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RESERVE_SPACE(8);
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WRITE32(op->opnum);
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statp = p++; /* to be backfilled at the end */
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post_err_offset = xdr->buf->len;
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if (op->opnum == OP_ILLEGAL)
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goto status;
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@ -3698,20 +3706,19 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
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* bug if we had to do this on a non-idempotent op:
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*/
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warn_on_nonidempotent_op(op);
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resp->xdr.p = statp + 1;
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xdr_truncate_encode(xdr, post_err_offset);
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}
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if (so) {
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int len = xdr->buf->len - post_err_offset;
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so->so_replay.rp_status = op->status;
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so->so_replay.rp_buflen = (char *)resp->xdr.p
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- (char *)(statp+1);
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memcpy(so->so_replay.rp_buf, statp+1, so->so_replay.rp_buflen);
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so->so_replay.rp_buflen = len;
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read_bytes_from_xdr_buf(xdr->buf, post_err_offset,
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so->so_replay.rp_buf, len);
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}
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status:
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/*
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* Note: We write the status directly, instead of using WRITE32(),
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* since it is already in network byte order.
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*/
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*statp = op->status;
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/* Note that op->status is already in network byte order: */
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write_bytes_to_xdr_buf(xdr->buf, post_err_offset - 4, &op->status, 4);
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}
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/*
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