Many kernel drivers contain code that allocates and frees both a
scatterlist and the pages that populate that scatterlist.
Introduce functions in lib/scatterlist.c that perform these tasks
instead of duplicating this functionality in multiple drivers.
Only include these functions in the build if CONFIG_SGL_ALLOC=y
to avoid that the kernel size increases if this functionality is
not used.
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Reviewed-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
---
include/linux/scatterlist.h | 10 +++++
lib/Kconfig | 4 ++
lib/scatterlist.c | 105 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 119 insertions(+)
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)
--
2.15.1
