lib/scatterlist: Introduce sgl_alloc() and sgl_free()

commit e80a0af4759a164214f02da157a3800753ce135f upstream.

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@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index d87dfa41142d4d7770b6774b5f19681293862656..8b7bce207229cb1ee4e5ee78e74e7fb8ecfc77ec 100644 (file)
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -267,6 +267,16 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
        unsigned long 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 b1445b22a6def496d91bde16deb2b13a01a52915..8396c4cfa1aba31491e624f091a56e87d4d139e1 100644 (file)
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -413,6 +413,10 @@ 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 355f2e90b72c8307f78b47757bfc6ae74fd4cdff..11fce289d116675c341478893a5ad263c87c4793 100644 (file)
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -433,6 +433,111 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 }
 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)