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Commit e80a0af4 authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

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



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: default avatarBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent bbbc3c1c

include/linux/scatterlist.h

+10 −0
Original line number Diff line number Diff line
@@ -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);

lib/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -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)

lib/scatterlist.c

+105 −0
Original line number Diff line number Diff line
@@ -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)