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>

1 files changed, 11 insertions, 11 deletions

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 0898752cecfe..cd85c492c267 100644
--- 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);