+/*
+ * allocate a virtually contiguous buffer and create a scatterlist describing it
+ * @sg_table - pointer to a place to be filled with sg_table contents
+ * @size - required buffer size
+ */
+static void *ffs_build_sg_list(struct sg_table *sgt, size_t sz)
+{
+ struct page **pages;
+ void *vaddr, *ptr;
+ unsigned int n_pages;
+ int i;
+
+ vaddr = vmalloc(sz);
+ if (!vaddr)
+ return NULL;
+
+ n_pages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ pages = kvmalloc_array(n_pages, sizeof(struct page *), GFP_KERNEL);
+ if (!pages) {
+ vfree(vaddr);
+
+ return NULL;
+ }
+ for (i = 0, ptr = vaddr; i < n_pages; ++i, ptr += PAGE_SIZE)
+ pages[i] = vmalloc_to_page(ptr);
+
+ if (sg_alloc_table_from_pages(sgt, pages, n_pages, 0, sz, GFP_KERNEL)) {
+ kvfree(pages);
+ vfree(vaddr);
+
+ return NULL;
+ }
+ kvfree(pages);
+
+ return vaddr;
+}
+
+static inline void *ffs_alloc_buffer(struct ffs_io_data *io_data,
+ size_t data_len)
+{
+ if (io_data->use_sg)
+ return ffs_build_sg_list(&io_data->sgt, data_len);
+
+ return kmalloc(data_len, GFP_KERNEL);
+}
+
+static inline void ffs_free_buffer(struct ffs_io_data *io_data)
+{
+ if (!io_data->buf)
+ return;
+
+ if (io_data->use_sg) {
+ sg_free_table(&io_data->sgt);
+ vfree(io_data->buf);
+ } else {
+ kfree(io_data->buf);
+ }
+}
+