From: Anna Schumaker <[email protected]>
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: Anna Schumaker <[email protected]>
---
include/linux/sunrpc/xdr.h | 1 +
net/sunrpc/xdr.c | 73 ++++++++++++++++++++++++++++++++++++++
2 files changed, 74 insertions(+)
diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index 026edbd041d5..36a81c29542e 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -252,6 +252,7 @@ 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
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index d8c9555c6f2b..24baf052e6e6 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -390,6 +390,42 @@ _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);
+
+ pgbase += zero;
+ if (pgbase == PAGE_SIZE) {
+ flush_dcache_page(*page);
+ pgbase = 0;
+ page++;
+ }
+
+ } while ((len -= zero) != 0);
+ flush_dcache_page(*page);
+}
+
/**
* xdr_shrink_bufhead
* @buf: xdr_buf
@@ -1141,6 +1177,43 @@ 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
--
2.28.0