[PATCH v3 4/6] SUNRPC: Introduce xdr_buf_nth_page_address()

Anna Schumaker
2022-07-15T18:44:41Z

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

For getting a pointer to the memory address represented by the nth page,
along with the length of the data on that page.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
include/linux/sunrpc/xdr.h | 2 ++
net/sunrpc/xdr.c | 17 +++++++++++++++++
2 files changed, 19 insertions(+)

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index bdaf048edde0..79824fea4529 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -137,6 +137,8 @@ void xdr_inline_pages(struct xdr_buf *, unsigned int,
struct page **, unsigned int, unsigned int);
void xdr_terminate_string(const struct xdr_buf *, const u32);
size_t xdr_buf_pagecount(const struct xdr_buf *buf);
+char *xdr_buf_nth_page_address(const struct xdr_buf *buf, unsigned int n,
+ unsigned int *len);
int xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp);
void xdr_free_bvec(struct xdr_buf *buf);

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 37956a274f81..88b28656a05d 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -140,6 +140,23 @@ size_t xdr_buf_pagecount(const struct xdr_buf *buf)
return (buf->page_base + buf->page_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
}

+char *xdr_buf_nth_page_address(const struct xdr_buf *buf, unsigned int n,
+ unsigned int *len)
+{
+ unsigned int pgbase = buf->page_base + (n * PAGE_SIZE);
+ struct page **pages = buf->pages;
+ struct page **page;
+
+ if (n >= xdr_buf_pagecount(buf))
+ return NULL;
+
+ page = pages + (pgbase >> PAGE_SHIFT);
+ pgbase &= ~PAGE_MASK;
+ *len = min_t(size_t, PAGE_SIZE, buf->page_len - (n * PAGE_SIZE));
+ return page_address(*page) + pgbase;
+}
+EXPORT_SYMBOL_GPL(xdr_buf_nth_page_address);
+
int
xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp)
{
--
2.37.1