SUNRPC: Fix up handling of the XDRBUF_SPARSE_PAGES flag

If the allocator fails before it has reached the target number of pages,
then we need to recheck that we're not seeking past the page buffer.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 0898752cecfebb0a5400c41953bea3cefcf74a29..cd85c492c267b3a827729ffd13687195843d5fc1 100644 (file)
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -330,18 +330,16 @@ xs_alloc_sparse_pages(struct xdr_buf *buf, size_t want, gfp_t gfp)
 {
        size_t i,n;
 
-       if (!(buf->flags & XDRBUF_SPARSE_PAGES))
+       if (!want || !(buf->flags & XDRBUF_SPARSE_PAGES))
                return want;
-       if (want > buf->page_len)
-               want = buf->page_len;
        n = (buf->page_base + want + PAGE_SIZE - 1) >> PAGE_SHIFT;
        for (i = 0; i < n; i++) {
                if (buf->pages[i])
                        continue;
                buf->bvec[i].bv_page = buf->pages[i] = alloc_page(gfp);
                if (!buf->pages[i]) {
-                       buf->page_len = (i * PAGE_SIZE) - buf->page_base;
-                       return buf->page_len;
+                       i *= PAGE_SIZE;
+                       return i > buf->page_base ? i - buf->page_base : 0;
                }
        }
        return want;
@@ -404,10 +402,11 @@ xs_read_xdr_buf(struct socket *sock, struct msghdr *msg, int flags,
                seek -= buf->head[0].iov_len;
                offset += buf->head[0].iov_len;
        }
-       if (seek < buf->page_len) {
-               want = xs_alloc_sparse_pages(buf,
-                               min_t(size_t, count - offset, buf->page_len),
-                               GFP_NOWAIT);
+
+       want = xs_alloc_sparse_pages(buf,
+                       min_t(size_t, count - offset, buf->page_len),
+                       GFP_NOWAIT);
+       if (seek < want) {
                ret = xs_read_bvec(sock, msg, flags, buf->bvec,
                                xdr_buf_pagecount(buf),
                                want + buf->page_base,
@@ -421,9 +420,10 @@ xs_read_xdr_buf(struct socket *sock, struct msghdr *msg, int flags,
                        goto out;
                seek = 0;
        } else {
-               seek -= buf->page_len;
-               offset += buf->page_len;
+               seek -= want;
+               offset += want;
        }
+
        if (seek < buf->tail[0].iov_len) {
                want = min_t(size_t, count - offset, buf->tail[0].iov_len);
                ret = xs_read_kvec(sock, msg, flags, &buf->tail[0], want, seek);