Commit 4f5f3b60 authored by Anna Schumaker's avatar Anna Schumaker Committed by Trond Myklebust
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SUNRPC: Introduce xdr_stream_move_subsegment() 



I do this by creating an xdr subsegment for the range we will be
operating over. This lets me shift data to the correct place without
potentially overwriting anything already there.

Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent 33ce83ef

include/linux/sunrpc/xdr.h

+2 −0
Original line number Diff line number Diff line
@@ -262,6 +262,8 @@ extern unsigned int xdr_align_data(struct xdr_stream *, unsigned int offset, uns 
extern unsigned int xdr_expand_hole(struct xdr_stream *, unsigned int offset, unsigned int length);

extern bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf,

				  unsigned int len);

extern unsigned int xdr_stream_move_subsegment(struct xdr_stream *xdr, unsigned int offset,

					       unsigned int target, unsigned int length);



/**

 * xdr_set_scratch_buffer - Attach a scratch buffer for decoding data.

net/sunrpc/xdr.c

+59 −0
Original line number Diff line number Diff line
@@ -775,6 +775,34 @@ static void xdr_buf_pages_shift_left(const struct xdr_buf *buf, 
	xdr_buf_tail_copy_left(buf, 0, len - buf->page_len, shift);

}



static void xdr_buf_head_shift_left(const struct xdr_buf *buf,

				    unsigned int base, unsigned int len,

				    unsigned int shift)

{

	const struct kvec *head = buf->head;

	unsigned int bytes;



	if (!shift || !len)

		return;



	if (shift > base) {

		bytes = (shift - base);

		if (bytes >= len)

			return;

		base += bytes;

		len -= bytes;

	}



	if (base < head->iov_len) {

		bytes = min_t(unsigned int, len, head->iov_len - base);

		memmove(head->iov_base + (base - shift),

			head->iov_base + base, bytes);

		base += bytes;

		len -= bytes;

	}

	xdr_buf_pages_shift_left(buf, base - head->iov_len, len, shift);

}



/**

 * xdr_shrink_bufhead

 * @buf: xdr_buf
@@ -1680,6 +1708,37 @@ bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf, 
}

EXPORT_SYMBOL_GPL(xdr_stream_subsegment);



/**

 * xdr_stream_move_subsegment - Move part of a stream to another position

 * @xdr: the source xdr_stream

 * @offset: the source offset of the segment

 * @target: the target offset of the segment

 * @length: the number of bytes to move

 *

 * Moves @length bytes from @offset to @target in the xdr_stream, overwriting

 * anything in its space. Returns the number of bytes in the segment.

 */

unsigned int xdr_stream_move_subsegment(struct xdr_stream *xdr, unsigned int offset,

					unsigned int target, unsigned int length)

{

	struct xdr_buf buf;

	unsigned int shift;



	if (offset < target) {

		shift = target - offset;

		if (xdr_buf_subsegment(xdr->buf, &buf, offset, shift + length) < 0)

			return 0;

		xdr_buf_head_shift_right(&buf, 0, length, shift);

	} else if (offset > target) {

		shift = offset - target;

		if (xdr_buf_subsegment(xdr->buf, &buf, target, shift + length) < 0)

			return 0;

		xdr_buf_head_shift_left(&buf, shift, length, shift);

	}

	return length;

}

EXPORT_SYMBOL_GPL(xdr_stream_move_subsegment);



/**

 * xdr_buf_trim - lop at most "len" bytes off the end of "buf"

 * @buf: buf to be trimmed