SUNRPC: When expanding the buffer, we may need grow the sparse pages

If we're shifting the page data to the right, and this happens to be a
sparse page array, then we may need to allocate new pages in order to
receive the data.

Reported-by: "Mkrtchyan, Tigran" <tigran.mkrtchyan@desy.de>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 2e91fbd..60d4442 100644 (file)
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -478,16 +478,47 @@ static void xdr_buf_pages_zero(const struct xdr_buf *buf, unsigned int pgbase,
        } while ((len -= zero) != 0);
 }
 
+static unsigned int xdr_buf_pages_fill_sparse(const struct xdr_buf *buf,
+                                             unsigned int buflen, gfp_t gfp)
+{
+       unsigned int i, npages, pagelen;
+
+       if (!(buf->flags & XDRBUF_SPARSE_PAGES))
+               return buflen;
+       if (buflen <= buf->head->iov_len)
+               return buflen;
+       pagelen = buflen - buf->head->iov_len;
+       if (pagelen > buf->page_len)
+               pagelen = buf->page_len;
+       npages = (pagelen + buf->page_base + PAGE_SIZE - 1) >> PAGE_SHIFT;
+       for (i = 0; i < npages; i++) {
+               if (!buf->pages[i])
+                       continue;
+               buf->pages[i] = alloc_page(gfp);
+               if (likely(buf->pages[i]))
+                       continue;
+               buflen -= pagelen;
+               pagelen = i << PAGE_SHIFT;
+               if (pagelen > buf->page_base)
+                       buflen += pagelen - buf->page_base;
+               break;
+       }
+       return buflen;
+}
+
 static void xdr_buf_try_expand(struct xdr_buf *buf, unsigned int len)
 {
        struct kvec *head = buf->head;
        struct kvec *tail = buf->tail;
        unsigned int sum = head->iov_len + buf->page_len + tail->iov_len;
-       unsigned int free_space;
+       unsigned int free_space, newlen;
 
        if (sum > buf->len) {
                free_space = min_t(unsigned int, sum - buf->len, len);
-               buf->len += free_space;
+               newlen = xdr_buf_pages_fill_sparse(buf, buf->len + free_space,
+                                                  GFP_KERNEL);
+               free_space = newlen - buf->len;
+               buf->len = newlen;
                len -= free_space;
                if (!len)
                        return;