Commit 84ce182a authored by Anna Schumaker's avatar Anna Schumaker
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SUNRPC: Add the ability to expand holes in data pages 



This patch adds the ability to "read a hole" into a set of XDR data
pages by taking the following steps:

1) Shift all data after the current xdr->p to the right, possibly into
   the tail,
2) Zero the specified range, and
3) Update xdr->p to point beyond the hole.

Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent 43f0f081

include/linux/sunrpc/xdr.h

+1 −0
Original line number Diff line number Diff line
@@ -250,6 +250,7 @@ extern __be32 *xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes); 
extern unsigned int xdr_read_pages(struct xdr_stream *xdr, unsigned int len);

extern void xdr_enter_page(struct xdr_stream *xdr, unsigned int len);

extern int xdr_process_buf(struct xdr_buf *buf, unsigned int offset, unsigned int len, int (*actor)(struct scatterlist *, void *), void *data);

extern uint64_t xdr_expand_hole(struct xdr_stream *, uint64_t, uint64_t);



/**

 * xdr_stream_remaining - Return the number of bytes remaining in the stream

net/sunrpc/xdr.c

+69 −0
Original line number Diff line number Diff line
@@ -390,6 +390,38 @@ _copy_from_pages(char *p, struct page **pages, size_t pgbase, size_t len) 
}

EXPORT_SYMBOL_GPL(_copy_from_pages);



/**

 * _zero_pages

 * @pages: array of pages

 * @pgbase: beginning page vector address

 * @len: length

 */

static void

_zero_pages(struct page **pages, size_t pgbase, size_t len)

{

	struct page **page;

	char *vpage;

	size_t zero;



	page = pages + (pgbase >> PAGE_SHIFT);

	pgbase &= ~PAGE_MASK;



	do {

		zero = PAGE_SIZE - pgbase;

		if (zero > len)

			zero = len;



		vpage = kmap_atomic(*page);

		memset(vpage + pgbase, 0, zero);

		kunmap_atomic(vpage);



		flush_dcache_page(*page);

		pgbase = 0;

		page++;



	} while ((len -= zero) != 0);

}



/**

 * xdr_shrink_bufhead

 * @buf: xdr_buf
@@ -1096,6 +1128,43 @@ unsigned int xdr_read_pages(struct xdr_stream *xdr, unsigned int len) 
}

EXPORT_SYMBOL_GPL(xdr_read_pages);



uint64_t xdr_expand_hole(struct xdr_stream *xdr, uint64_t offset, uint64_t length)

{

	struct xdr_buf *buf = xdr->buf;

	unsigned int bytes;

	unsigned int from;

	unsigned int truncated = 0;



	if ((offset + length) < offset ||

	    (offset + length) > buf->page_len)

		length = buf->page_len - offset;



	xdr_realign_pages(xdr);

	from = xdr_page_pos(xdr);

	bytes = xdr->nwords << 2;



	if (offset + length + bytes > buf->page_len) {

		unsigned int shift = (offset + length + bytes) - buf->page_len;

		unsigned int res = _shift_data_right_tail(buf, from + bytes - shift, shift);

		truncated = shift - res;

		xdr->nwords -= XDR_QUADLEN(truncated);

		bytes -= shift;

	}



	/* Now move the page data over and zero pages */

	if (bytes > 0)

		_shift_data_right_pages(buf->pages,

					buf->page_base + offset + length,

					buf->page_base + from,

					bytes);

	_zero_pages(buf->pages, buf->page_base + offset, length);



	buf->len += length - (from - offset) - truncated;

	xdr_set_page(xdr, offset + length, PAGE_SIZE);

	return length;

}

EXPORT_SYMBOL_GPL(xdr_expand_hole);



/**

 * xdr_enter_page - decode data from the XDR page

 * @xdr: pointer to xdr_stream struct