[PATCH 04/11] lib/scatterlist: Extract scatterlist allocation from __sg_alloc_table

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Separating out the allocation engine will come useful in the following
patch.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Bart Van Assche <bart.vanassche at wdc.com>
Cc: Hannes Reinecke <hare at suse.com>
Cc: Johannes Thumshirn <jthumshirn at suse.de>
Cc: Jens Axboe <axboe at kernel.dk>
---
 lib/scatterlist.c | 78 ++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 48 insertions(+), 30 deletions(-)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index ee4b9f0fe00b..e137de4c36c9 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -253,34 +253,20 @@ void sg_free_table(struct sg_table *table)
 }
 EXPORT_SYMBOL(sg_free_table);
 
-/**
- * __sg_alloc_table - Allocate and initialize an sg table with given allocator
- * @table:	The sg table header to use
- * @nents:	Number of entries in sg list
- * @max_ents:	The maximum number of entries the allocator returns per call
- * @gfp_mask:	GFP allocation mask
- * @alloc_fn:	Allocator to use
- *
- * Description:
- *   This function returns a @table @nents long. The allocator is
- *   defined to return scatterlist chunks of maximum size @max_ents.
- *   Thus if @nents is bigger than @max_ents, the scatterlists will be
- *   chained in units of @max_ents.
- *
- * Notes:
- *   If this function returns non-0 (eg failure), the caller must call
- *   __sg_free_table() to cleanup any leftover allocations.
- *
- **/
-int __sg_alloc_table(struct sg_table *table, unsigned int nents,
-		     unsigned int max_ents, struct scatterlist *first_chunk,
-		     gfp_t gfp_mask, sg_alloc_fn *alloc_fn)
-{
-	struct scatterlist *sg, *prv;
+static int
+__sg_alloc_scatterlist(unsigned int nents,
+		       unsigned int max_ents,
+		       struct scatterlist *first_chunk,
+		       gfp_t gfp_mask,
+		       sg_alloc_fn *alloc_fn,
+		       unsigned int *out_nents,
+		       unsigned int *out_orig_nents,
+		       struct scatterlist **out_sgl)
+{
+	struct scatterlist *sg, *prv, *_sgl = NULL;
+	unsigned int _nents = 0, _orig_nents = 0;
 	unsigned int left;
 
-	memset(table, 0, sizeof(*table));
-
 	if (nents == 0)
 		return -EINVAL;
 #ifndef CONFIG_ARCH_HAS_SG_CHAIN
@@ -315,13 +301,13 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 			 * confused.
 			 */
 			if (prv)
-				table->nents = ++table->orig_nents;
+				_nents = ++_orig_nents;
 
- 			return -ENOMEM;
+			return -ENOMEM;
 		}
 
 		sg_init_table(sg, alloc_size);
-		table->nents = table->orig_nents += sg_size;
+		_nents = _orig_nents += sg_size;
 
 		/*
 		 * If this is the first mapping, assign the sg table header.
@@ -330,7 +316,7 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 		if (prv)
 			sg_chain(prv, max_ents, sg);
 		else
-			table->sgl = sg;
+			_sgl = sg;
 
 		/*
 		 * If no more entries after this one, mark the end
@@ -341,8 +327,40 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 		prv = sg;
 	} while (left);
 
+	*out_nents = _nents;
+	*out_orig_nents = _orig_nents;
+	*out_sgl = _sgl;
+
 	return 0;
 }
+
+/**
+ * __sg_alloc_table - Allocate and initialize an sg table with given allocator
+ * @table:	The sg table header to use
+ * @nents:	Number of entries in sg list
+ * @max_ents:	The maximum number of entries the allocator returns per call
+ * @gfp_mask:	GFP allocation mask
+ * @alloc_fn:	Allocator to use
+ *
+ * Description:
+ *   This function returns a @table @nents long. The allocator is
+ *   defined to return scatterlist chunks of maximum size @max_ents.
+ *   Thus if @nents is bigger than @max_ents, the scatterlists will be
+ *   chained in units of @max_ents.
+ *
+ * Notes:
+ *   If this function returns non-0 (eg failure), the caller must call
+ *   __sg_free_table() to cleanup any leftover allocations.
+ *
+ **/
+int __sg_alloc_table(struct sg_table *table, unsigned int nents,
+		     unsigned int max_ents, struct scatterlist *first_chunk,
+		     gfp_t gfp_mask, sg_alloc_fn *alloc_fn)
+{
+	return __sg_alloc_scatterlist(nents, max_ents, first_chunk, gfp_mask,
+				      alloc_fn, &table->nents,
+				      &table->orig_nents, &table->sgl);
+}
 EXPORT_SYMBOL(__sg_alloc_table);
 
 /**
-- 
2.14.1