3 files changed, 119 insertions, 0 deletions

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index b7c83254c566..b8a7c1d1dbe3 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -276,6 +276,16 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
                               unsigned int n_pages, unsigned int offset,
                               unsigned long size, gfp_t gfp_mask);
 
+#ifdef CONFIG_SGL_ALLOC
+struct scatterlist *sgl_alloc_order(unsigned long long length,
+                                    unsigned int order, bool chainable,
+                                    gfp_t gfp, unsigned int *nent_p);
+struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
+                              unsigned int *nent_p);
+void sgl_free_order(struct scatterlist *sgl, int order);
+void sgl_free(struct scatterlist *sgl);
+#endif /* CONFIG_SGL_ALLOC */
+
 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
                       size_t buflen, off_t skip, bool to_buffer);
 
diff --git a/lib/Kconfig b/lib/Kconfig
index c5e84fbcb30b..4dd5c11366f9 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -409,6 +409,10 @@ config HAS_DMA
         depends on !NO_DMA
         default y
 
+config SGL_ALLOC
+        bool
+        default n
+
 config DMA_NOOP_OPS
         bool
         depends on HAS_DMA && (!64BIT || ARCH_DMA_ADDR_T_64BIT)
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 7c1c55f7daaa..9afc9b432083 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -474,6 +474,111 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 }
 EXPORT_SYMBOL(sg_alloc_table_from_pages);
 
+#ifdef CONFIG_SGL_ALLOC
+
+/**
+ * sgl_alloc_order - allocate a scatterlist and its pages
+ * @length: Length in bytes of the scatterlist. Must be at least one
+ * @order: Second argument for alloc_pages()
+ * @chainable: Whether or not to allocate an extra element in the scatterlist
+ *      for scatterlist chaining purposes
+ * @gfp: Memory allocation flags
+ * @nent_p: [out] Number of entries in the scatterlist that have pages
+ *
+ * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
+ */
+struct scatterlist *sgl_alloc_order(unsigned long long length,
+                                    unsigned int order, bool chainable,
+                                    gfp_t gfp, unsigned int *nent_p)
+{
+        struct scatterlist *sgl, *sg;
+        struct page *page;
+        unsigned int nent, nalloc;
+        u32 elem_len;
+
+        nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order);
+        /* Check for integer overflow */
+        if (length > (nent << (PAGE_SHIFT + order)))
+                return NULL;
+        nalloc = nent;
+        if (chainable) {
+                /* Check for integer overflow */
+                if (nalloc + 1 < nalloc)
+                        return NULL;
+                nalloc++;
+        }
+        sgl = kmalloc_array(nalloc, sizeof(struct scatterlist),
+                            (gfp & ~GFP_DMA) | __GFP_ZERO);
+        if (!sgl)
+                return NULL;
+
+        sg_init_table(sgl, nent);
+        sg = sgl;
+        while (length) {
+                elem_len = min_t(u64, length, PAGE_SIZE << order);
+                page = alloc_pages(gfp, order);
+                if (!page) {
+                        sgl_free(sgl);
+                        return NULL;
+                }
+
+                sg_set_page(sg, page, elem_len, 0);
+                length -= elem_len;
+                sg = sg_next(sg);
+        }
+        WARN_ON_ONCE(sg);
+        if (nent_p)
+                *nent_p = nent;
+        return sgl;
+}
+EXPORT_SYMBOL(sgl_alloc_order);
+
+/**
+ * sgl_alloc - allocate a scatterlist and its pages
+ * @length: Length in bytes of the scatterlist
+ * @gfp: Memory allocation flags
+ * @nent_p: [out] Number of entries in the scatterlist
+ *
+ * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
+ */
+struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
+                              unsigned int *nent_p)
+{
+        return sgl_alloc_order(length, 0, false, gfp, nent_p);
+}
+EXPORT_SYMBOL(sgl_alloc);
+
+/**
+ * sgl_free_order - free a scatterlist and its pages
+ * @sgl: Scatterlist with one or more elements
+ * @order: Second argument for __free_pages()
+ */
+void sgl_free_order(struct scatterlist *sgl, int order)
+{
+        struct scatterlist *sg;
+        struct page *page;
+
+        for (sg = sgl; sg; sg = sg_next(sg)) {
+                page = sg_page(sg);
+                if (page)
+                        __free_pages(page, order);
+        }
+        kfree(sgl);
+}
+EXPORT_SYMBOL(sgl_free_order);
+
+/**
+ * sgl_free - free a scatterlist and its pages
+ * @sgl: Scatterlist with one or more elements
+ */
+void sgl_free(struct scatterlist *sgl)
+{
+        sgl_free_order(sgl, 0);
+}
+EXPORT_SYMBOL(sgl_free);
+
+#endif /* CONFIG_SGL_ALLOC */
+
 void __sg_page_iter_start(struct sg_page_iter *piter,
                           struct scatterlist *sglist, unsigned int nents,
                           unsigned long pgoffset)