Merge tag 'scsi-sg' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

Pull SCSI scatter-gather list updates from James Bottomley:
 "This topic branch covers a fundamental change in how our sg lists are
  allocated to make mq more efficient by reducing the size of the
  preallocated sg list.

  This necessitates a large number of driver changes because the
  previous guarantee that if a driver specified SG_ALL as the size of
  its scatter list, it would get a non-chained list and didn't need to
  bother with scatterlist iterators is now broken and every driver
  *must* use scatterlist iterators.

  This was broken out as a separate topic because we need to convert all
  the drivers before pulling the trigger and unconverted drivers kept
  being found, necessitating a rebase"

* tag 'scsi-sg' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (21 commits)
  scsi: core: don't preallocate small SGL in case of NO_SG_CHAIN
  scsi: lib/sg_pool.c: clear 'first_chunk' in case of no preallocation
  scsi: core: avoid preallocating big SGL for data
  scsi: core: avoid preallocating big SGL for protection information
  scsi: lib/sg_pool.c: improve APIs for allocating sg pool
  scsi: esp: use sg helper to iterate over scatterlist
  scsi: NCR5380: use sg helper to iterate over scatterlist
  scsi: wd33c93: use sg helper to iterate over scatterlist
  scsi: ppa: use sg helper to iterate over scatterlist
  scsi: pcmcia: nsp_cs: use sg helper to iterate over scatterlist
  scsi: imm: use sg helper to iterate over scatterlist
  scsi: aha152x: use sg helper to iterate over scatterlist
  scsi: s390: zfcp_fc: use sg helper to iterate over scatterlist
  scsi: staging: unisys: visorhba: use sg helper to iterate over scatterlist
  scsi: usb: image: microtek: use sg helper to iterate over scatterlist
  scsi: pmcraid: use sg helper to iterate over scatterlist
  scsi: ipr: use sg helper to iterate over scatterlist
  scsi: mvumi: use sg helper to iterate over scatterlist
  scsi: lpfc: use sg helper to iterate over scatterlist
  scsi: advansys: use sg helper to iterate over scatterlist
  ...

2 files changed, 52 insertions, 23 deletions

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index eacb82468437..c2cf2c311b7d 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -179,7 +179,8 @@ static void sg_kfree(struct scatterlist *sg, unsigned int nents)
  * __sg_free_table - Free a previously mapped sg table
  * @table:	The sg table header to use
  * @max_ents:	The maximum number of entries per single scatterlist
- * @skip_first_chunk: don't free the (preallocated) first scatterlist chunk
+ * @nents_first_chunk: Number of entries int the (preallocated) first
+ * 	scatterlist chunk, 0 means no such preallocated first chunk
  * @free_fn:	Free function
  *
  *  Description:
@@ -189,9 +190,10 @@ static void sg_kfree(struct scatterlist *sg, unsigned int nents)
  *
  **/
 void __sg_free_table(struct sg_table *table, unsigned int max_ents,
-		     bool skip_first_chunk, sg_free_fn *free_fn)
+		     unsigned int nents_first_chunk, sg_free_fn *free_fn)
 {
 	struct scatterlist *sgl, *next;
+	unsigned curr_max_ents = nents_first_chunk ?: max_ents;
 
 	if (unlikely(!table->sgl))
 		return;
@@ -207,9 +209,9 @@ void __sg_free_table(struct sg_table *table, unsigned int max_ents,
 		 * sg_size is then one less than alloc size, since the last
 		 * element is the chain pointer.
 		 */
-		if (alloc_size > max_ents) {
-			next = sg_chain_ptr(&sgl[max_ents - 1]);
-			alloc_size = max_ents;
+		if (alloc_size > curr_max_ents) {
+			next = sg_chain_ptr(&sgl[curr_max_ents - 1]);
+			alloc_size = curr_max_ents;
 			sg_size = alloc_size - 1;
 		} else {
 			sg_size = alloc_size;
@@ -217,11 +219,12 @@ void __sg_free_table(struct sg_table *table, unsigned int max_ents,
 		}
 
 		table->orig_nents -= sg_size;
-		if (skip_first_chunk)
-			skip_first_chunk = false;
+		if (nents_first_chunk)
+			nents_first_chunk = 0;
 		else
 			free_fn(sgl, alloc_size);
 		sgl = next;
+		curr_max_ents = max_ents;
 	}
 
 	table->sgl = NULL;
@@ -244,6 +247,8 @@ EXPORT_SYMBOL(sg_free_table);
  * @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
+ * @nents_first_chunk: Number of entries int the (preallocated) first
+ * 	scatterlist chunk, 0 means no such preallocated chunk provided by user
  * @gfp_mask:	GFP allocation mask
  * @alloc_fn:	Allocator to use
  *
@@ -260,10 +265,13 @@ EXPORT_SYMBOL(sg_free_table);
  **/
 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)
+		     unsigned int nents_first_chunk, gfp_t gfp_mask,
+		     sg_alloc_fn *alloc_fn)
 {
 	struct scatterlist *sg, *prv;
 	unsigned int left;
+	unsigned curr_max_ents = nents_first_chunk ?: max_ents;
+	unsigned prv_max_ents;
 
 	memset(table, 0, sizeof(*table));
 
@@ -279,8 +287,8 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 	do {
 		unsigned int sg_size, alloc_size = left;
 
-		if (alloc_size > max_ents) {
-			alloc_size = max_ents;
+		if (alloc_size > curr_max_ents) {
+			alloc_size = curr_max_ents;
 			sg_size = alloc_size - 1;
 		} else
 			sg_size = alloc_size;
@@ -314,7 +322,7 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 		 * If this is not the first mapping, chain previous part.
 		 */
 		if (prv)
-			sg_chain(prv, max_ents, sg);
+			sg_chain(prv, prv_max_ents, sg);
 		else
 			table->sgl = sg;
 
@@ -325,6 +333,8 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 			sg_mark_end(&sg[sg_size - 1]);
 
 		prv = sg;
+		prv_max_ents = curr_max_ents;
+		curr_max_ents = max_ents;
 	} while (left);
 
 	return 0;
@@ -347,9 +357,9 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
 	int ret;
 
 	ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
-			       NULL, gfp_mask, sg_kmalloc);
+			       NULL, 0, gfp_mask, sg_kmalloc);
 	if (unlikely(ret))
-		__sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree);
+		__sg_free_table(table, SG_MAX_SINGLE_ALLOC, 0, sg_kfree);
 
 	return ret;
 }
diff --git a/lib/sg_pool.c b/lib/sg_pool.c
index cff20df2695e..db29e5c1f790 100644
--- a/lib/sg_pool.c
+++ b/lib/sg_pool.c
@@ -70,18 +70,27 @@ static struct scatterlist *sg_pool_alloc(unsigned int nents, gfp_t gfp_mask)
 /**
  * sg_free_table_chained - Free a previously mapped sg table
  * @table:	The sg table header to use
- * @first_chunk: was first_chunk not NULL in sg_alloc_table_chained?
+ * @nents_first_chunk: size of the first_chunk SGL passed to
+ *		sg_alloc_table_chained
  *
  *  Description:
  *    Free an sg table previously allocated and setup with
  *    sg_alloc_table_chained().
  *
+ *    @nents_first_chunk has to be same with that same parameter passed
+ *    to sg_alloc_table_chained().
+ *
  **/
-void sg_free_table_chained(struct sg_table *table, bool first_chunk)
+void sg_free_table_chained(struct sg_table *table,
+		unsigned nents_first_chunk)
 {
-	if (first_chunk && table->orig_nents <= SG_CHUNK_SIZE)
+	if (table->orig_nents <= nents_first_chunk)
 		return;
-	__sg_free_table(table, SG_CHUNK_SIZE, first_chunk, sg_pool_free);
+
+	if (nents_first_chunk == 1)
+		nents_first_chunk = 0;
+
+	__sg_free_table(table, SG_CHUNK_SIZE, nents_first_chunk, sg_pool_free);
 }
 EXPORT_SYMBOL_GPL(sg_free_table_chained);
 
@@ -90,31 +99,41 @@ EXPORT_SYMBOL_GPL(sg_free_table_chained);
  * @table:	The sg table header to use
  * @nents:	Number of entries in sg list
  * @first_chunk: first SGL
+ * @nents_first_chunk: number of the SGL of @first_chunk
  *
  *  Description:
  *    Allocate and chain SGLs in an sg table. If @nents@ is larger than
- *    SG_CHUNK_SIZE a chained sg table will be setup.
+ *    @nents_first_chunk a chained sg table will be setup. @first_chunk is
+ *    ignored if nents_first_chunk <= 1 because user expects the SGL points
+ *    non-chain SGL.
  *
  **/
 int sg_alloc_table_chained(struct sg_table *table, int nents,
-		struct scatterlist *first_chunk)
+		struct scatterlist *first_chunk, unsigned nents_first_chunk)
 {
 	int ret;
 
 	BUG_ON(!nents);
 
-	if (first_chunk) {
-		if (nents <= SG_CHUNK_SIZE) {
+	if (first_chunk && nents_first_chunk) {
+		if (nents <= nents_first_chunk) {
 			table->nents = table->orig_nents = nents;
 			sg_init_table(table->sgl, nents);
 			return 0;
 		}
 	}
 
+	/* User supposes that the 1st SGL includes real entry */
+	if (nents_first_chunk <= 1) {
+		first_chunk = NULL;
+		nents_first_chunk = 0;
+	}
+
 	ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE,
-			       first_chunk, GFP_ATOMIC, sg_pool_alloc);
+			       first_chunk, nents_first_chunk,
+			       GFP_ATOMIC, sg_pool_alloc);
 	if (unlikely(ret))
-		sg_free_table_chained(table, (bool)first_chunk);
+		sg_free_table_chained(table, nents_first_chunk);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(sg_alloc_table_chained);