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[PATCH 1/4] scatterlist: Introduce some helper functions

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  [PATCH 1/4] scatterlist: Introduce some helper functions Baolin Wang <baolin.wang@linaro.org> - 2016-03-03 06:30 +0100
    Re: [PATCH 1/4] scatterlist: Introduce some helper functions Robert Jarzmik <robert.jarzmik@free.fr> - 2016-03-03 20:20 +0100
      Re: [PATCH 1/4] scatterlist: Introduce some helper functions Baolin Wang <baolin.wang@linaro.org> - 2016-03-04 07:30 +0100
        Re: [PATCH 1/4] scatterlist: Introduce some helper functions Baolin Wang <baolin.wang@linaro.org> - 2016-03-04 08:00 +0100

#1348790 — [PATCH 1/4] scatterlist: Introduce some helper functions

In crypto engine framework, one request can combine other requests'
scatterlists into its sg table to improve engine efficency with
handling bulk block. Thus we need some helper functions to manage
dynamic scattertables.

This patch introduces 'sg_is_contiguous()' function to check if two
scatterlists are contiguous, 'sg_alloc_empty_table()' function to
allocate one empty sg table, 'sg_add_sg_to_table()' function to add
one scatterlist into sg table and 'sg_table_is_empty' function to
check if the sg table is empty.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
 include/linux/scatterlist.h |   33 ++++++++++++++++++++++++
 lib/scatterlist.c           |   59 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 556ec1e..ae9aee6 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -212,6 +212,37 @@ static inline void sg_unmark_end(struct scatterlist *sg)
 }
 
 /**
+ * sg_is_contiguous - Check if the scatterlists are contiguous
+ * @sga: SG entry
+ * @sgb: SG entry
+ *
+ * Description:
+ *   If the sga scatterlist is contiguous with the sgb scatterlist,
+ *   that means they can be merged together.
+ *
+ **/
+static inline bool sg_is_contiguous(struct scatterlist *sga,
+				    struct scatterlist *sgb)
+{
+	return ((sga->page_link & ~0x3UL) + sga->offset + sga->length ==
+		(sgb->page_link & ~0x3UL));
+}
+
+/**
+ * sg_table_is_empty - Check if the sg table is empty
+ * @sgt: sg table
+ *
+ * Description:
+ *   The 'orig_nents' member of one sg table is used to indicate how many
+ *   scatterlists in the sg table.
+ *
+ **/
+static inline bool sg_table_is_empty(struct sg_table *sgt)
+{
+	return !sgt->orig_nents;
+}
+
+/**
  * sg_phys - Return physical address of an sg entry
  * @sg:	     SG entry
  *
@@ -261,6 +292,8 @@ void sg_free_table(struct sg_table *);
 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 		     struct scatterlist *, gfp_t, sg_alloc_fn *);
 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
+int sg_alloc_empty_table(struct sg_table *, unsigned int, gfp_t);
+int sg_add_sg_to_table(struct sg_table *, struct scatterlist *);
 int sg_alloc_table_from_pages(struct sg_table *sgt,
 	struct page **pages, unsigned int n_pages,
 	unsigned long offset, unsigned long size,
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 004fc70..e9e5d5a 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -370,6 +370,65 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
 EXPORT_SYMBOL(sg_alloc_table);
 
 /**
+ * sg_add_sg_to_table - Add one scatterlist into sg table
+ * @sgt:	The sg table header to use
+ * @src:	The sg need to be added into sg table
+ *
+ * Description:
+ *   The 'nents' member indicates how many scatterlists added in the sg table.
+ *   Copy the @src@ scatterlist into sg table and increase 'nents' member.
+ *
+ **/
+int sg_add_sg_to_table(struct sg_table *sgt, struct scatterlist *src)
+{
+	unsigned int i = 0, orig_nents = sgt->orig_nents;
+	struct scatterlist *sgl = sgt->sgl;
+	struct scatterlist *sg;
+
+	/* Check if there are enough space for the new sg to be added */
+	if (sgt->nents >= sgt->orig_nents)
+		return -EINVAL;
+
+	for_each_sg(sgl, sg, orig_nents, i) {
+		if (sgt->nents > 0 && i == (sgt->nents - 1)) {
+			sg_unmark_end(sg);
+		} else if (i == sgt->nents) {
+			memcpy(sg, src, sizeof(struct scatterlist));
+			sg_mark_end(sg);
+			sgt->nents++;
+			break;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * sg_alloc_empty_table - Allocate one empty sg table
+ * @sgt:	The sg table header to use
+ * @nents:	Number of entries in sg list
+ * @gfp_mask:	GFP allocation mask
+ *
+ *  Description:
+ *    Allocate and initialize an sg table. The 'nents' member of sg_table
+ *    indicates how many scatterlists added in the sg table. It should set
+ *    0 which means there are no scatterlists added in this sg table now.
+ *
+ **/
+int sg_alloc_empty_table(struct sg_table *sgt, unsigned int nents,
+			 gfp_t gfp_mask)
+{
+	int ret;
+
+	ret = sg_alloc_table(sgt, nents, gfp_mask);
+	if (ret)
+		return ret;
+
+	sgt->nents = 0;
+	return 0;
+}
+
+/**
  * sg_alloc_table_from_pages - Allocate and initialize an sg table from
  *			       an array of pages
  * @sgt:	The sg table header to use
-- 
1.7.9.5

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#1349522

Baolin Wang <baolin.wang@linaro.org> writes:

> @@ -212,6 +212,37 @@ static inline void sg_unmark_end(struct scatterlist *sg)
>  }
>  
>  /**
> + * sg_is_contiguous - Check if the scatterlists are contiguous
> + * @sga: SG entry
> + * @sgb: SG entry
> + *
> + * Description:
> + *   If the sga scatterlist is contiguous with the sgb scatterlist,
> + *   that means they can be merged together.
> + *
> + **/
> +static inline bool sg_is_contiguous(struct scatterlist *sga,
> +				    struct scatterlist *sgb)
> +{
> +	return ((sga->page_link & ~0x3UL) + sga->offset + sga->length ==
> +		(sgb->page_link & ~0x3UL));
> +}
I don't understand that one.
sga->page_link is a pointer to a "struct page *". How can it be added to an
offset within a page ???

> @@ -370,6 +370,65 @@ int sg_alloc_table(struct sg_table *table, unsigned int
> nents, gfp_t gfp_mask)
...
>  /**
> + * sg_add_sg_to_table - Add one scatterlist into sg table
> + * @sgt:	The sg table header to use
> + * @src:	The sg need to be added into sg table
> + *
> + * Description:
> + *   The 'nents' member indicates how many scatterlists added in the sg table.
> + *   Copy the @src@ scatterlist into sg table and increase 'nents' member.
> + *
> + **/
> +int sg_add_sg_to_table(struct sg_table *sgt, struct scatterlist *src)
> +{
> +	unsigned int i = 0, orig_nents = sgt->orig_nents;
> +	struct scatterlist *sgl = sgt->sgl;
> +	struct scatterlist *sg;
> +
> +	/* Check if there are enough space for the new sg to be added */
> +	if (sgt->nents >= sgt->orig_nents)
> +		return -EINVAL;
I must admit I don't understand that one either : how do comparing the number of
"mapped" entries against the number of "allocated" entries determines if there
is enough room ?

> +/**
> + * sg_alloc_empty_table - Allocate one empty sg table
> + * @sgt:	The sg table header to use
> + * @nents:	Number of entries in sg list
> + * @gfp_mask:	GFP allocation mask
> + *
> + *  Description:
> + *    Allocate and initialize an sg table. The 'nents' member of sg_table
> + *    indicates how many scatterlists added in the sg table. It should set
> + *    0 which means there are no scatterlists added in this sg table now.
> + *
> + **/
> +int sg_alloc_empty_table(struct sg_table *sgt, unsigned int nents,
> +			 gfp_t gfp_mask)
As for this one, there has to be a purpose for it I fail to see. From far away
it looks exactly like sg_alloc_table(), excepting it "works around" the nents >
0 protection of __sg_alloc_table().
What is exactly the need for this one, and if it's usefull why not simply
changing the __sg_alloc_table() "nents > 0" test and see what the outcome of the
review will be ?

Cheers.

-- 
Robert

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#1349877

Hi Robert,

On 4 March 2016 at 03:15, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
> Baolin Wang <baolin.wang@linaro.org> writes:
>
>> @@ -212,6 +212,37 @@ static inline void sg_unmark_end(struct scatterlist *sg)
>>  }
>>
>>  /**
>> + * sg_is_contiguous - Check if the scatterlists are contiguous
>> + * @sga: SG entry
>> + * @sgb: SG entry
>> + *
>> + * Description:
>> + *   If the sga scatterlist is contiguous with the sgb scatterlist,
>> + *   that means they can be merged together.
>> + *
>> + **/
>> +static inline bool sg_is_contiguous(struct scatterlist *sga,
>> +                                 struct scatterlist *sgb)
>> +{
>> +     return ((sga->page_link & ~0x3UL) + sga->offset + sga->length ==
>> +             (sgb->page_link & ~0x3UL));
>> +}
> I don't understand that one.
> sga->page_link is a pointer to a "struct page *". How can it be added to an
> offset within a page ???


Ah, sorry that's a mistake. It should check as below:
static inline bool sg_is_contiguous(struct scatterlist *sga, struct
scatterlist *sgb)
{
    return (unsigned int)sg_virt(sga) + sga->length == (unsigned
int)sg_virt(sgb);
}

>
>> @@ -370,6 +370,65 @@ int sg_alloc_table(struct sg_table *table, unsigned int
>> nents, gfp_t gfp_mask)
> ...
>>  /**
>> + * sg_add_sg_to_table - Add one scatterlist into sg table
>> + * @sgt:     The sg table header to use
>> + * @src:     The sg need to be added into sg table
>> + *
>> + * Description:
>> + *   The 'nents' member indicates how many scatterlists added in the sg table.
>> + *   Copy the @src@ scatterlist into sg table and increase 'nents' member.
>> + *
>> + **/
>> +int sg_add_sg_to_table(struct sg_table *sgt, struct scatterlist *src)
>> +{
>> +     unsigned int i = 0, orig_nents = sgt->orig_nents;
>> +     struct scatterlist *sgl = sgt->sgl;
>> +     struct scatterlist *sg;
>> +
>> +     /* Check if there are enough space for the new sg to be added */
>> +     if (sgt->nents >= sgt->orig_nents)
>> +             return -EINVAL;
> I must admit I don't understand that one either : how do comparing the number of
> "mapped" entries against the number of "allocated" entries determines if there
> is enough room ?

That's for a dynamic sg table. If there is one sg table allocated
'orig_nents' scatterlists, and we need copy another mapped scatterlist
into the sg table if there are some requirements. So we use 'nents' to
record how many scatterlists have been copied into the sg table.

>
>> +/**
>> + * sg_alloc_empty_table - Allocate one empty sg table
>> + * @sgt:     The sg table header to use
>> + * @nents:   Number of entries in sg list
>> + * @gfp_mask:        GFP allocation mask
>> + *
>> + *  Description:
>> + *    Allocate and initialize an sg table. The 'nents' member of sg_table
>> + *    indicates how many scatterlists added in the sg table. It should set
>> + *    0 which means there are no scatterlists added in this sg table now.
>> + *
>> + **/
>> +int sg_alloc_empty_table(struct sg_table *sgt, unsigned int nents,
>> +                      gfp_t gfp_mask)
> As for this one, there has to be a purpose for it I fail to see. From far away
> it looks exactly like sg_alloc_table(), excepting it "works around" the nents >
> 0 protection of __sg_alloc_table().
> What is exactly the need for this one, and if it's usefull why not simply
> changing the __sg_alloc_table() "nents > 0" test and see what the outcome of the
> review will be ?

Like I said above. If we want to copy some mapped scatterlists into
one sg table, we should set the 'nents' to 0 to indicates how many
scatterlists coppied in the sg table.
Thanks for your comments.

>
> Cheers.
>
> --
> Robert



-- 
Baolin.wang
Best Regards

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#1349900

>>> + **/
>>> +static inline bool sg_is_contiguous(struct scatterlist *sga,
>>> +                                 struct scatterlist *sgb)
>>> +{
>>> +     return ((sga->page_link & ~0x3UL) + sga->offset + sga->length ==
>>> +             (sgb->page_link & ~0x3UL));
>>> +}
>> I don't understand that one.
>> sga->page_link is a pointer to a "struct page *". How can it be added to an
>> offset within a page ???
>
>
> Ah, sorry that's a mistake. It should check as below:
> static inline bool sg_is_contiguous(struct scatterlist *sga, struct
> scatterlist *sgb)
> {
>     return (unsigned int)sg_virt(sga) + sga->length == (unsigned
> int)sg_virt(sgb);
> }

sorry, it should be:
static inline bool sg_is_contiguous(struct scatterlist *sga,
   struct scatterlist *sgb)
{
    return (unsigned long)sg_virt(sga) + sga->length ==
               (unsigned long)sg_virt(sgb);
}

-- 
Baolin.wang
Best Regards

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