+/*
+ * Should be used for buffers allocated with ceph_kvmalloc().
+ * Currently these are encrypt out-buffer (ceph_buffer) and decrypt
+ * in-buffer (msg front).
+ *
+ * Dispose of @sgt with teardown_sgtable().
+ *
+ * @prealloc_sg is to avoid memory allocation inside sg_alloc_table()
+ * in cases where a single sg is sufficient. No attempt to reduce the
+ * number of sgs by squeezing physically contiguous pages together is
+ * made though, for simplicity.
+ */
+static int setup_sgtable(struct sg_table *sgt, struct scatterlist *prealloc_sg,
+ const void *buf, unsigned int buf_len)
+{
+ struct scatterlist *sg;
+ const bool is_vmalloc = is_vmalloc_addr(buf);
+ unsigned int off = offset_in_page(buf);
+ unsigned int chunk_cnt = 1;
+ unsigned int chunk_len = PAGE_ALIGN(off + buf_len);
+ int i;
+ int ret;
+
+ if (buf_len == 0) {
+ memset(sgt, 0, sizeof(*sgt));
+ return -EINVAL;
+ }
+
+ if (is_vmalloc) {
+ chunk_cnt = chunk_len >> PAGE_SHIFT;
+ chunk_len = PAGE_SIZE;
+ }
+
+ if (chunk_cnt > 1) {
+ ret = sg_alloc_table(sgt, chunk_cnt, GFP_NOFS);
+ if (ret)
+ return ret;
+ } else {
+ WARN_ON(chunk_cnt != 1);
+ sg_init_table(prealloc_sg, 1);
+ sgt->sgl = prealloc_sg;
+ sgt->nents = sgt->orig_nents = 1;
+ }
+
+ for_each_sg(sgt->sgl, sg, sgt->orig_nents, i) {
+ struct page *page;
+ unsigned int len = min(chunk_len - off, buf_len);
+
+ if (is_vmalloc)
+ page = vmalloc_to_page(buf);
+ else
+ page = virt_to_page(buf);
+
+ sg_set_page(sg, page, len, off);
+
+ off = 0;
+ buf += len;
+ buf_len -= len;
+ }
+ WARN_ON(buf_len != 0);
+
+ return 0;
+}
+
+static void teardown_sgtable(struct sg_table *sgt)
+{
+ if (sgt->orig_nents > 1)
+ sg_free_table(sgt);
+}
+