rpc: Allow xdr_buf_subsegment to operate in-place
Allow xdr_buf_subsegment(&buf, &buf, base, len) to modify an xdr_buf in-place. Also, none of the callers need the iov_base of head or tail to be zeroed out. Also add documentation. (As it turns out, I'm not really using this new guarantee, but it seems a simple way to make this function a bit more robust.) Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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@ -833,8 +833,20 @@ xdr_buf_from_iov(struct kvec *iov, struct xdr_buf *buf)
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}
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EXPORT_SYMBOL_GPL(xdr_buf_from_iov);
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/* Sets subbuf to the portion of buf of length len beginning base bytes
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* from the start of buf. Returns -1 if base of length are out of bounds. */
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/**
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* xdr_buf_subsegment - set subbuf to a portion of buf
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* @buf: an xdr buffer
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* @subbuf: the result buffer
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* @base: beginning of range in bytes
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* @len: length of range in bytes
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*
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* sets @subbuf to an xdr buffer representing the portion of @buf of
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* length @len starting at offset @base.
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*
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* @buf and @subbuf may be pointers to the same struct xdr_buf.
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*
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* Returns -1 if base of length are out of bounds.
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*/
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int
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xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
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unsigned int base, unsigned int len)
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@ -847,9 +859,8 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
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len -= subbuf->head[0].iov_len;
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base = 0;
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} else {
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subbuf->head[0].iov_base = NULL;
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subbuf->head[0].iov_len = 0;
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base -= buf->head[0].iov_len;
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subbuf->head[0].iov_len = 0;
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}
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if (base < buf->page_len) {
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@ -871,9 +882,8 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
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len -= subbuf->tail[0].iov_len;
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base = 0;
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} else {
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subbuf->tail[0].iov_base = NULL;
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subbuf->tail[0].iov_len = 0;
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base -= buf->tail[0].iov_len;
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subbuf->tail[0].iov_len = 0;
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}
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if (base || len)
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