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scatterlist cleanups

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  scatterlist cleanups Christoph Hellwig <hch@lst.de> - 2015-08-07 18:20 +0200
    [PATCH 4/6] scatterlist: remove open coded sg_unmark_end instances Christoph Hellwig <hch@lst.de> - 2015-08-07 18:20 +0200
    [PATCH 1/6] scatterlist: allow limited chaining without ARCH_HAS_SG_CHAIN Christoph Hellwig <hch@lst.de> - 2015-08-07 18:20 +0200
    [PATCH 2/6] target/rd: always chain S/G list Christoph Hellwig <hch@lst.de> - 2015-08-07 18:30 +0200

#1202866 — scatterlist cleanups

This series contains various scatterlist cleanups.  It makes the chained
scatterlist helpers generally available, even if a architecture doesn't
allow a DMA mapping for it, and changes two callers to make use of this
as well as cleans up various opencoded access to scatterlist internals.

A large part of this work is based on older patches from Dan.

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#1202868 — [PATCH 4/6] scatterlist: remove open coded sg_unmark_end instances

From: Dan Williams <dan.j.williams@intel.com>

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
[hch: split from a larger patch by Dan]
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-merge.c        | 2 +-
 drivers/mmc/card/queue.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 30a0d9f..f4a3e87 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -266,7 +266,7 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 		if (rq->cmd_flags & REQ_WRITE)
 			memset(q->dma_drain_buffer, 0, q->dma_drain_size);
 
-		sg->page_link &= ~0x02;
+		sg_unmark_end(sg);
 		sg = sg_next(sg);
 		sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
 			    q->dma_drain_size,
diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index b5a2b14..9b214da 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -467,7 +467,7 @@ static unsigned int mmc_queue_packed_map_sg(struct mmc_queue *mq,
 			sg_set_buf(__sg, buf + offset, len);
 			offset += len;
 			remain -= len;
-			(__sg++)->page_link &= ~0x02;
+			sg_unmark_end(__sg++);
 			sg_len++;
 		} while (remain);
 	}
@@ -475,7 +475,7 @@ static unsigned int mmc_queue_packed_map_sg(struct mmc_queue *mq,
 	list_for_each_entry(req, &packed->list, queuelist) {
 		sg_len += blk_rq_map_sg(mq->queue, req, __sg);
 		__sg = sg + (sg_len - 1);
-		(__sg++)->page_link &= ~0x02;
+		sg_unmark_end(__sg++);
 	}
 	sg_mark_end(sg + (sg_len - 1));
 	return sg_len;
-- 
1.9.1

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#1202871 — [PATCH 1/6] scatterlist: allow limited chaining without ARCH_HAS_SG_CHAIN

There are a couple of uses of struct scatterlist that never go to
the dma_map_sg() helper and thus don't care about ARCH_HAS_SG_CHAIN
which indicates that we can map chained S/G list.

The most important one is the crypto code, which currently has
to open code a few helpers to always allow chaining.  This patch
removes a few #ifdef ARCH_HAS_SG_CHAIN statements so that we can
switch the crypto code to these common helpers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/scatterlist.h | 4 ----
 lib/scatterlist.c           | 4 ----
 2 files changed, 8 deletions(-)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 9b1ef0c..698e906 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -161,10 +161,6 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 			    struct scatterlist *sgl)
 {
-#ifndef CONFIG_ARCH_HAS_SG_CHAIN
-	BUG();
-#endif
-
 	/*
 	 * offset and length are unused for chain entry.  Clear them.
 	 */
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index d105a9f..bafa993 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -105,16 +105,12 @@ EXPORT_SYMBOL(sg_nents_for_len);
  **/
 struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
 {
-#ifndef CONFIG_ARCH_HAS_SG_CHAIN
-	struct scatterlist *ret = &sgl[nents - 1];
-#else
 	struct scatterlist *sg, *ret = NULL;
 	unsigned int i;
 
 	for_each_sg(sgl, sg, nents, i)
 		ret = sg;
 
-#endif
 #ifdef CONFIG_DEBUG_SG
 	BUG_ON(sgl[0].sg_magic != SG_MAGIC);
 	BUG_ON(!sg_is_last(ret));
-- 
1.9.1

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#1202877 — [PATCH 2/6] target/rd: always chain S/G list

The rd sg lists are never passed to hardware, so use S/G chaining
unonditionally.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/target/target_core_rd.c | 44 -----------------------------------------
 1 file changed, 44 deletions(-)

diff --git a/drivers/target/target_core_rd.c b/drivers/target/target_core_rd.c
index 4703f40..badd927 100644
--- a/drivers/target/target_core_rd.c
+++ b/drivers/target/target_core_rd.c
@@ -138,16 +138,12 @@ static int rd_allocate_sgl_table(struct rd_dev *rd_dev, struct rd_dev_sg_table *
 		sg_per_table = (total_sg_needed > max_sg_per_table) ?
 			max_sg_per_table : total_sg_needed;
 
-#ifdef CONFIG_ARCH_HAS_SG_CHAIN
-
 		/*
 		 * Reserve extra element for chain entry
 		 */
 		if (sg_per_table < total_sg_needed)
 			chain_entry = 1;
 
-#endif /* CONFIG_ARCH_HAS_SG_CHAIN */
-
 		sg = kcalloc(sg_per_table + chain_entry, sizeof(*sg),
 				GFP_KERNEL);
 		if (!sg) {
@@ -158,15 +154,11 @@ static int rd_allocate_sgl_table(struct rd_dev *rd_dev, struct rd_dev_sg_table *
 
 		sg_init_table(sg, sg_per_table + chain_entry);
 
-#ifdef CONFIG_ARCH_HAS_SG_CHAIN
-
 		if (i > 0) {
 			sg_chain(sg_table[i - 1].sg_table,
 				 max_sg_per_table + 1, sg);
 		}
 
-#endif /* CONFIG_ARCH_HAS_SG_CHAIN */
-
 		sg_table[i].sg_table = sg;
 		sg_table[i].rd_sg_count = sg_per_table;
 		sg_table[i].page_start_offset = page_offset;
@@ -429,42 +421,6 @@ static sense_reason_t rd_do_prot_rw(struct se_cmd *cmd, bool is_read)
 	prot_sg = &prot_table->sg_table[prot_page -
 					prot_table->page_start_offset];
 
-#ifndef CONFIG_ARCH_HAS_SG_CHAIN
-
-	prot_npages = DIV_ROUND_UP(prot_offset + sectors * se_dev->prot_length,
-				   PAGE_SIZE);
-
-	/*
-	 * Allocate temporaly contiguous scatterlist entries if prot pages
-	 * straddles multiple scatterlist tables.
-	 */
-	if (prot_table->page_end_offset < prot_page + prot_npages - 1) {
-		int i;
-
-		prot_sg = kcalloc(prot_npages, sizeof(*prot_sg), GFP_KERNEL);
-		if (!prot_sg)
-			return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
-
-		need_to_release = true;
-		sg_init_table(prot_sg, prot_npages);
-
-		for (i = 0; i < prot_npages; i++) {
-			if (prot_page + i > prot_table->page_end_offset) {
-				prot_table = rd_get_prot_table(dev,
-								prot_page + i);
-				if (!prot_table) {
-					kfree(prot_sg);
-					return rc;
-				}
-				sg_unmark_end(&prot_sg[i - 1]);
-			}
-			prot_sg[i] = prot_table->sg_table[prot_page + i -
-						prot_table->page_start_offset];
-		}
-	}
-
-#endif /* !CONFIG_ARCH_HAS_SG_CHAIN */
-
 	if (is_read)
 		rc = sbc_dif_verify(cmd, cmd->t_task_lba, sectors, 0,
 				    prot_sg, prot_offset);
-- 
1.9.1

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