Re: [PATCH v2 1/8] lib/scatterlist: Introduce sgl_alloc() and sgl_free()

[Johannes Thumshirn]

Thanks Bart,
Reviewed-by: Johannes Thumshirn 
-- 
Johannes Thumshirn  Storage
jthumsh...@suse.de+49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH v2 1/8] lib/scatterlist: Introduce sgl_alloc() and sgl_free()

[Hannes Reinecke]

On 10/17/2017 12:49 AM, Bart Van Assche wrote:
> 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 
> ---
>  include/linux/scatterlist.h |  10 +
>  lib/Kconfig |   4 ++
>  lib/scatterlist.c   | 105 
> 
>  3 files changed, 119 insertions(+)
> 

Reviewed-by: Hannes Reinecke 

Cheers,

Hannes
-- 
Dr. Hannes ReineckeTeamlead Storage & Networking
h...@suse.de   +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)

[PATCH v2 1/8] lib/scatterlist: Introduce sgl_alloc() and sgl_free()

[Bart Van Assche]

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 
---
 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 4b3286ac60c8..3642511918d5 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -266,6 +266,16 @@ 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 b1445b22a6de..8396c4cfa1ab 100644
--- 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 be7b4dd6b68d..e2b5a78ceb44 100644
--- 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;
+