[PATCH V3 00/15] use sg helper to operate scatterlist

[PATCH V3 00/15] use sg helper to operate scatterlist

[Ming Lei]

Hi,

Scsi MQ makes a large static allocation for the first scatter gather
list chunk for the driver to use.  This is a performance headache we'd
like to fix by reducing the size of the allocation to a 2 element
array.  Doing this will break the current guarantee that any driver
using SG_ALL doesn't need to use the scatterlist iterators and can get
away with directly dereferencing the array.  Thus we need to update all
drivers to use the scatterlist iterators and remove direct indexing of
the scatterlist array before reducing the initial scatterlist
allocation size in SCSI.

So convert drivers to use scatterlist helper.

There are two types of scsi SGL uses:

1) operate on scsi_sglist(scmd) directly, then one local variable of
'struct scatterlist *' is involved, so the following coccinelle semantic
patch is developed for finding this type of direct sgl uses:

	https://marc.info/?l=linux-scsi&m=156031374809852&w=2

2) scsi_sglist(scmd) is stored to cmd->SCp.buffer and the SGL is used
via cmd->SCp.buffer. Simple 'grep SCp.buffer' is used for finding SGL
direct uses, fortunately only the following drivers uses SCp.buffer to
store SGL:

	NCR5380, aha152x, arm/, imm, pcmcia, ppa and wd33c93

And arm/ is already ready to handle chained SGL.

The 1st 9 patches are for handling type #1, and the other 6 patches
for handling type #2.

V3:
	- update commit log and cover letter, most of words are from
	James Bottomley	

V2:
	- use coccinelle semantic patch for finding direct sgl uses from
	scsi command(9 drivers found)
	- run 'git grep -E "SCp.buffer"' to find direct sgl uses
	from SCp.buffer(6 drivers are found)

Finn Thain (1):
  NCR5380: Support chained sg lists

Ming Lei (14):
  scsi: vmw_pscsi: use sg helper to operate scatterlist
  scsi: advansys: use sg helper to operate scatterlist
  scsi: lpfc: use sg helper to operate scatterlist
  scsi: mvumi: use sg helper to operate scatterlist
  scsi: ipr: use sg helper to operate scatterlist
  scsi: pmcraid: use sg helper to operate scatterlist
  usb: image: microtek: use sg helper to operate scatterlist
  staging: unisys: visorhba: use sg helper to operate scatterlist
  s390: zfcp_fc: use sg helper to operate scatterlist
  scsi: aha152x: use sg helper to operate scatterlist
  scsi: imm: use sg helper to operate scatterlist
  scsi: pcmcia: nsp_cs: use sg helper to operate scatterlist
  scsi: ppa: use sg helper to operate scatterlist
  scsi: wd33c93: use sg helper to operate scatterlist

 drivers/s390/scsi/zfcp_fc.c                   |  4 +-
 drivers/scsi/NCR5380.c                        | 41 ++++++++-----------
 drivers/scsi/advansys.c                       |  2 +-
 drivers/scsi/aha152x.c                        | 29 ++++++++-----
 drivers/scsi/imm.c                            |  2 +-
 drivers/scsi/ipr.c                            | 28 +++++++------
 drivers/scsi/lpfc/lpfc_nvmet.c                |  3 +-
 drivers/scsi/mvumi.c                          |  9 ++--
 drivers/scsi/pcmcia/nsp_cs.c                  |  4 +-
 drivers/scsi/pmcraid.c                        | 12 +++---
 drivers/scsi/ppa.c                            |  2 +-
 drivers/scsi/vmw_pvscsi.c                     |  2 +-
 drivers/scsi/wd33c93.c                        |  2 +-
 .../staging/unisys/visorhba/visorhba_main.c   |  9 ++--
 drivers/usb/image/microtek.c                  | 20 ++++-----
 drivers/usb/image/microtek.h                  |  2 +-
 16 files changed, 85 insertions(+), 86 deletions(-)

-- 
2.20.1

[PATCH V3 01/15] scsi: vmw_pscsi: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the scatterlist
array.

This way allows us to pre-allocate one small scatterlist, which can be chained
with one runtime allocated scatterlist if the pre-allocated one isn't enough
for the whole request.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/vmw_pvscsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/vmw_pvscsi.c b/drivers/scsi/vmw_pvscsi.c
index ecee4b3ff073..d71abd416eb4 100644
--- a/drivers/scsi/vmw_pvscsi.c
+++ b/drivers/scsi/vmw_pvscsi.c
@@ -335,7 +335,7 @@ static void pvscsi_create_sg(struct pvscsi_ctx *ctx,
 	BUG_ON(count > PVSCSI_MAX_NUM_SG_ENTRIES_PER_SEGMENT);
 
 	sge = &ctx->sgl->sge[0];
-	for (i = 0; i < count; i++, sg++) {
+	for (i = 0; i < count; i++, sg = sg_next(sg)) {
 		sge[i].addr   = sg_dma_address(sg);
 		sge[i].length = sg_dma_len(sg);
 		sge[i].flags  = 0;
-- 
2.20.1

[PATCH V3 02/15] scsi: advansys: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/advansys.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/advansys.c b/drivers/scsi/advansys.c
index d37584403c33..b87de8d3d844 100644
--- a/drivers/scsi/advansys.c
+++ b/drivers/scsi/advansys.c
@@ -7714,7 +7714,7 @@ adv_get_sglist(struct asc_board *boardp, adv_req_t *reqp,
 				sg_block->sg_ptr = 0L; /* Last ADV_SG_BLOCK in list. */
 				return ADV_SUCCESS;
 			}
-			slp++;
+			slp = sg_next(slp);
 		}
 		sg_block->sg_cnt = NO_OF_SG_PER_BLOCK;
 		prev_sg_block = sg_block;
-- 
2.20.1

[PATCH V3 03/15] scsi: lpfc: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one isn't
enough for the whole request.

Reviewed by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/lpfc/lpfc_nvmet.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_nvmet.c b/drivers/scsi/lpfc/lpfc_nvmet.c
index f3d9a5545164..3f803982bd1e 100644
--- a/drivers/scsi/lpfc/lpfc_nvmet.c
+++ b/drivers/scsi/lpfc/lpfc_nvmet.c
@@ -2887,8 +2887,7 @@ lpfc_nvmet_prep_fcp_wqe(struct lpfc_hba *phba,
 	nvmewqe->drvrTimeout = (phba->fc_ratov * 3) + LPFC_DRVR_TIMEOUT;
 	nvmewqe->context1 = ndlp;
 
-	for (i = 0; i < rsp->sg_cnt; i++) {
-		sgel = &rsp->sg[i];
+	for_each_sg(rsp->sg, sgel, rsp->sg_cnt, i) {
 		physaddr = sg_dma_address(sgel);
 		cnt = sg_dma_len(sgel);
 		sgl->addr_hi = putPaddrHigh(physaddr);
-- 
2.20.1

[PATCH V3 04/15] scsi: mvumi: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/mvumi.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/mvumi.c b/drivers/scsi/mvumi.c
index a5410615edac..0022cd31500a 100644
--- a/drivers/scsi/mvumi.c
+++ b/drivers/scsi/mvumi.c
@@ -211,8 +211,7 @@ static int mvumi_make_sgl(struct mvumi_hba *mhba, struct scsi_cmnd *scmd,
 	unsigned int sgnum = scsi_sg_count(scmd);
 	dma_addr_t busaddr;
 
-	sg = scsi_sglist(scmd);
-	*sg_count = dma_map_sg(&mhba->pdev->dev, sg, sgnum,
+	*sg_count = dma_map_sg(&mhba->pdev->dev, scsi_sglist(scmd), sgnum,
 			       scmd->sc_data_direction);
 	if (*sg_count > mhba->max_sge) {
 		dev_err(&mhba->pdev->dev,
@@ -222,12 +221,12 @@ static int mvumi_make_sgl(struct mvumi_hba *mhba, struct scsi_cmnd *scmd,
 			     scmd->sc_data_direction);
 		return -1;
 	}
-	for (i = 0; i < *sg_count; i++) {
-		busaddr = sg_dma_address(&sg[i]);
+	scsi_for_each_sg(scmd, sg, *sg_count, i) {
+		busaddr = sg_dma_address(sg);
 		m_sg->baseaddr_l = cpu_to_le32(lower_32_bits(busaddr));
 		m_sg->baseaddr_h = cpu_to_le32(upper_32_bits(busaddr));
 		m_sg->flags = 0;
-		sgd_setsz(mhba, m_sg, cpu_to_le32(sg_dma_len(&sg[i])));
+		sgd_setsz(mhba, m_sg, cpu_to_le32(sg_dma_len(sg)));
 		if ((i + 1) == *sg_count)
 			m_sg->flags |= 1U << mhba->eot_flag;
 
-- 
2.20.1

[PATCH V3 05/15] scsi: ipr: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/ipr.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c
index 6d053e220153..383603973937 100644
--- a/drivers/scsi/ipr.c
+++ b/drivers/scsi/ipr.c
@@ -3915,22 +3915,22 @@ static int ipr_copy_ucode_buffer(struct ipr_sglist *sglist,
 				 u8 *buffer, u32 len)
 {
 	int bsize_elem, i, result = 0;
-	struct scatterlist *scatterlist;
+	struct scatterlist *sg;
 	void *kaddr;
 
 	/* Determine the actual number of bytes per element */
 	bsize_elem = PAGE_SIZE * (1 << sglist->order);
 
-	scatterlist = sglist->scatterlist;
+	sg = sglist->scatterlist;
 
-	for (i = 0; i < (len / bsize_elem); i++, buffer += bsize_elem) {
-		struct page *page = sg_page(&scatterlist[i]);
+	for (i = 0; i < (len / bsize_elem); i++, sg = sg_next(sg), buffer += bsize_elem) {
+		struct page *page = sg_page(sg);
 
 		kaddr = kmap(page);
 		memcpy(kaddr, buffer, bsize_elem);
 		kunmap(page);
 
-		scatterlist[i].length = bsize_elem;
+		sg->length = bsize_elem;
 
 		if (result != 0) {
 			ipr_trace;
@@ -3939,13 +3939,13 @@ static int ipr_copy_ucode_buffer(struct ipr_sglist *sglist,
 	}
 
 	if (len % bsize_elem) {
-		struct page *page = sg_page(&scatterlist[i]);
+		struct page *page = sg_page(sg);
 
 		kaddr = kmap(page);
 		memcpy(kaddr, buffer, len % bsize_elem);
 		kunmap(page);
 
-		scatterlist[i].length = len % bsize_elem;
+		sg->length = len % bsize_elem;
 	}
 
 	sglist->buffer_len = len;
@@ -3966,6 +3966,7 @@ static void ipr_build_ucode_ioadl64(struct ipr_cmnd *ipr_cmd,
 	struct ipr_ioarcb *ioarcb = &ipr_cmd->ioarcb;
 	struct ipr_ioadl64_desc *ioadl64 = ipr_cmd->i.ioadl64;
 	struct scatterlist *scatterlist = sglist->scatterlist;
+	struct scatterlist *sg;
 	int i;
 
 	ipr_cmd->dma_use_sg = sglist->num_dma_sg;
@@ -3974,10 +3975,10 @@ static void ipr_build_ucode_ioadl64(struct ipr_cmnd *ipr_cmd,
 
 	ioarcb->ioadl_len =
 		cpu_to_be32(sizeof(struct ipr_ioadl64_desc) * ipr_cmd->dma_use_sg);
-	for (i = 0; i < ipr_cmd->dma_use_sg; i++) {
+	for_each_sg(scatterlist, sg, ipr_cmd->dma_use_sg, i) {
 		ioadl64[i].flags = cpu_to_be32(IPR_IOADL_FLAGS_WRITE);
-		ioadl64[i].data_len = cpu_to_be32(sg_dma_len(&scatterlist[i]));
-		ioadl64[i].address = cpu_to_be64(sg_dma_address(&scatterlist[i]));
+		ioadl64[i].data_len = cpu_to_be32(sg_dma_len(sg));
+		ioadl64[i].address = cpu_to_be64(sg_dma_address(sg));
 	}
 
 	ioadl64[i-1].flags |= cpu_to_be32(IPR_IOADL_FLAGS_LAST);
@@ -3997,6 +3998,7 @@ static void ipr_build_ucode_ioadl(struct ipr_cmnd *ipr_cmd,
 	struct ipr_ioarcb *ioarcb = &ipr_cmd->ioarcb;
 	struct ipr_ioadl_desc *ioadl = ipr_cmd->i.ioadl;
 	struct scatterlist *scatterlist = sglist->scatterlist;
+	struct scatterlist *sg;
 	int i;
 
 	ipr_cmd->dma_use_sg = sglist->num_dma_sg;
@@ -4006,11 +4008,11 @@ static void ipr_build_ucode_ioadl(struct ipr_cmnd *ipr_cmd,
 	ioarcb->ioadl_len =
 		cpu_to_be32(sizeof(struct ipr_ioadl_desc) * ipr_cmd->dma_use_sg);
 
-	for (i = 0; i < ipr_cmd->dma_use_sg; i++) {
+	for_each_sg(scatterlist, sg, ipr_cmd->dma_use_sg, i) {
 		ioadl[i].flags_and_data_len =
-			cpu_to_be32(IPR_IOADL_FLAGS_WRITE | sg_dma_len(&scatterlist[i]));
+			cpu_to_be32(IPR_IOADL_FLAGS_WRITE | sg_dma_len(sg));
 		ioadl[i].address =
-			cpu_to_be32(sg_dma_address(&scatterlist[i]));
+			cpu_to_be32(sg_dma_address(sg));
 	}
 
 	ioadl[i-1].flags_and_data_len |=
-- 
2.20.1

[PATCH V3 06/15] scsi: pmcraid: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/pmcraid.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/pmcraid.c b/drivers/scsi/pmcraid.c
index e338d7a4f571..922c6e4b7eb3 100644
--- a/drivers/scsi/pmcraid.c
+++ b/drivers/scsi/pmcraid.c
@@ -3270,7 +3270,7 @@ static int pmcraid_copy_sglist(
 	int direction
 )
 {
-	struct scatterlist *scatterlist;
+	struct scatterlist *sg;
 	void *kaddr;
 	int bsize_elem;
 	int i;
@@ -3281,8 +3281,8 @@ static int pmcraid_copy_sglist(
 
 	scatterlist = sglist->scatterlist;
 
-	for (i = 0; i < (len / bsize_elem); i++, buffer += bsize_elem) {
-		struct page *page = sg_page(&scatterlist[i]);
+	for (i = 0; i < (len / bsize_elem); i++, sg = sg_next(sg), buffer += bsize_elem) {
+		struct page *page = sg_page(sg);
 
 		kaddr = kmap(page);
 		if (direction == DMA_TO_DEVICE)
@@ -3297,11 +3297,11 @@ static int pmcraid_copy_sglist(
 			return -EFAULT;
 		}
 
-		scatterlist[i].length = bsize_elem;
+		sg->length = bsize_elem;
 	}
 
 	if (len % bsize_elem) {
-		struct page *page = sg_page(&scatterlist[i]);
+		struct page *page = sg_page(sg);
 
 		kaddr = kmap(page);
 
@@ -3312,7 +3312,7 @@ static int pmcraid_copy_sglist(
 
 		kunmap(page);
 
-		scatterlist[i].length = len % bsize_elem;
+		sg->length = len % bsize_elem;
 	}
 
 	if (rc) {
-- 
2.20.1

[PATCH V3 07/15] usb: image: microtek: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Cc: Oliver Neukum <oliver@neukum.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/usb/image/microtek.c | 20 ++++++++------------
 drivers/usb/image/microtek.h |  2 +-
 2 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/image/microtek.c b/drivers/usb/image/microtek.c
index 607be1f4fe27..0a57c2cc8e5a 100644
--- a/drivers/usb/image/microtek.c
+++ b/drivers/usb/image/microtek.c
@@ -488,7 +488,6 @@ static void mts_command_done( struct urb *transfer )
 
 static void mts_do_sg (struct urb* transfer)
 {
-	struct scatterlist * sg;
 	int status = transfer->status;
 	MTS_INT_INIT();
 
@@ -500,13 +499,12 @@ static void mts_do_sg (struct urb* transfer)
 		mts_transfer_cleanup(transfer);
         }
 
-	sg = scsi_sglist(context->srb);
-	context->fragment++;
+	context->curr_sg = sg_next(context->curr_sg);
 	mts_int_submit_urb(transfer,
 			   context->data_pipe,
-			   sg_virt(&sg[context->fragment]),
-			   sg[context->fragment].length,
-			   context->fragment + 1 == scsi_sg_count(context->srb) ?
+			   sg_virt(context->curr_sg),
+			   context->curr_sg->length,
+			   sg_is_last(context->curr_sg) ?
 			   mts_data_done : mts_do_sg);
 }
 
@@ -526,22 +524,20 @@ static void
 mts_build_transfer_context(struct scsi_cmnd *srb, struct mts_desc* desc)
 {
 	int pipe;
-	struct scatterlist * sg;
-	
+
 	MTS_DEBUG_GOT_HERE();
 
 	desc->context.instance = desc;
 	desc->context.srb = srb;
-	desc->context.fragment = 0;
 
 	if (!scsi_bufflen(srb)) {
 		desc->context.data = NULL;
 		desc->context.data_length = 0;
 		return;
 	} else {
-		sg = scsi_sglist(srb);
-		desc->context.data = sg_virt(&sg[0]);
-		desc->context.data_length = sg[0].length;
+		desc->context.curr_sg = scsi_sglist(srb);
+		desc->context.data = sg_virt(desc->context.curr_sg);
+		desc->context.data_length = desc->context.curr_sg->length;
 	}
 
 
diff --git a/drivers/usb/image/microtek.h b/drivers/usb/image/microtek.h
index 66685e59241a..7bd5f4639c4a 100644
--- a/drivers/usb/image/microtek.h
+++ b/drivers/usb/image/microtek.h
@@ -21,7 +21,7 @@ struct mts_transfer_context
 	void *data;
 	unsigned data_length;
 	int data_pipe;
-	int fragment;
+	struct scatterlist *curr_sg;
 
 	u8 *scsi_status; /* status returned from ep_response after command completion */
 };
-- 
2.20.1

Re: [PATCH V3 07/15] usb: image: microtek: use sg helper to operate scatterlist

[Finn Thain]

On Fri, 14 Jun 2019, Ming Lei wrote:

> Use the scatterlist iterators and remove direct indexing of the
> scatterlist array.
> 
> This way allows us to pre-allocate one small scatterlist, which can be
> chained with one runtime allocated scatterlist if the pre-allocated one
> isn't enough for the whole request.
> 
> Cc: Oliver Neukum <oliver@neukum.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-usb@vger.kernel.org
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/usb/image/microtek.c | 20 ++++++++------------
>  drivers/usb/image/microtek.h |  2 +-
>  2 files changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/usb/image/microtek.c b/drivers/usb/image/microtek.c
> index 607be1f4fe27..0a57c2cc8e5a 100644
> --- a/drivers/usb/image/microtek.c
> +++ b/drivers/usb/image/microtek.c
> @@ -488,7 +488,6 @@ static void mts_command_done( struct urb *transfer )
>  
>  static void mts_do_sg (struct urb* transfer)
>  {
> -	struct scatterlist * sg;
>  	int status = transfer->status;
>  	MTS_INT_INIT();
>  
> @@ -500,13 +499,12 @@ static void mts_do_sg (struct urb* transfer)
>  		mts_transfer_cleanup(transfer);
>          }
>  
> -	sg = scsi_sglist(context->srb);
> -	context->fragment++;
> +	context->curr_sg = sg_next(context->curr_sg);
>  	mts_int_submit_urb(transfer,
>  			   context->data_pipe,
> -			   sg_virt(&sg[context->fragment]),
> -			   sg[context->fragment].length,
> -			   context->fragment + 1 == scsi_sg_count(context->srb) ?
> +			   sg_virt(context->curr_sg),
> +			   context->curr_sg->length,
> +			   sg_is_last(context->curr_sg) ?
>  			   mts_data_done : mts_do_sg);
>  }
>  
> @@ -526,22 +524,20 @@ static void
>  mts_build_transfer_context(struct scsi_cmnd *srb, struct mts_desc* desc)
>  {
>  	int pipe;
> -	struct scatterlist * sg;
> -	
> +
>  	MTS_DEBUG_GOT_HERE();
>  
>  	desc->context.instance = desc;
>  	desc->context.srb = srb;
> -	desc->context.fragment = 0;
>  
>  	if (!scsi_bufflen(srb)) {
>  		desc->context.data = NULL;
>  		desc->context.data_length = 0;
>  		return;
>  	} else {
> -		sg = scsi_sglist(srb);
> -		desc->context.data = sg_virt(&sg[0]);
> -		desc->context.data_length = sg[0].length;
> +		desc->context.curr_sg = scsi_sglist(srb);
> +		desc->context.data = sg_virt(desc->context.curr_sg);
> +		desc->context.data_length = desc->context.curr_sg->length;
>  	}
>  

Would it not be better to initialize desc->context.curr_sg in both 
branches of this conditional?

-- 

>  
> diff --git a/drivers/usb/image/microtek.h b/drivers/usb/image/microtek.h
> index 66685e59241a..7bd5f4639c4a 100644
> --- a/drivers/usb/image/microtek.h
> +++ b/drivers/usb/image/microtek.h
> @@ -21,7 +21,7 @@ struct mts_transfer_context
>  	void *data;
>  	unsigned data_length;
>  	int data_pipe;
> -	int fragment;
> +	struct scatterlist *curr_sg;
>  
>  	u8 *scsi_status; /* status returned from ep_response after command completion */
>  };
> 

Re: [PATCH V3 07/15] usb: image: microtek: use sg helper to operate scatterlist

[Ming Lei]

On Fri, Jun 14, 2019 at 03:39:10PM +1000, Finn Thain wrote:
> On Fri, 14 Jun 2019, Ming Lei wrote:
> 
> > Use the scatterlist iterators and remove direct indexing of the
> > scatterlist array.
> > 
> > This way allows us to pre-allocate one small scatterlist, which can be
> > chained with one runtime allocated scatterlist if the pre-allocated one
> > isn't enough for the whole request.
> > 
> > Cc: Oliver Neukum <oliver@neukum.org>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: linux-usb@vger.kernel.org
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> >  drivers/usb/image/microtek.c | 20 ++++++++------------
> >  drivers/usb/image/microtek.h |  2 +-
> >  2 files changed, 9 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/usb/image/microtek.c b/drivers/usb/image/microtek.c
> > index 607be1f4fe27..0a57c2cc8e5a 100644
> > --- a/drivers/usb/image/microtek.c
> > +++ b/drivers/usb/image/microtek.c
> > @@ -488,7 +488,6 @@ static void mts_command_done( struct urb *transfer )
> >  
> >  static void mts_do_sg (struct urb* transfer)
> >  {
> > -	struct scatterlist * sg;
> >  	int status = transfer->status;
> >  	MTS_INT_INIT();
> >  
> > @@ -500,13 +499,12 @@ static void mts_do_sg (struct urb* transfer)
> >  		mts_transfer_cleanup(transfer);
> >          }
> >  
> > -	sg = scsi_sglist(context->srb);
> > -	context->fragment++;
> > +	context->curr_sg = sg_next(context->curr_sg);
> >  	mts_int_submit_urb(transfer,
> >  			   context->data_pipe,
> > -			   sg_virt(&sg[context->fragment]),
> > -			   sg[context->fragment].length,
> > -			   context->fragment + 1 == scsi_sg_count(context->srb) ?
> > +			   sg_virt(context->curr_sg),
> > +			   context->curr_sg->length,
> > +			   sg_is_last(context->curr_sg) ?
> >  			   mts_data_done : mts_do_sg);
> >  }
> >  
> > @@ -526,22 +524,20 @@ static void
> >  mts_build_transfer_context(struct scsi_cmnd *srb, struct mts_desc* desc)
> >  {
> >  	int pipe;
> > -	struct scatterlist * sg;
> > -	
> > +
> >  	MTS_DEBUG_GOT_HERE();
> >  
> >  	desc->context.instance = desc;
> >  	desc->context.srb = srb;
> > -	desc->context.fragment = 0;
> >  
> >  	if (!scsi_bufflen(srb)) {
> >  		desc->context.data = NULL;
> >  		desc->context.data_length = 0;
> >  		return;
> >  	} else {
> > -		sg = scsi_sglist(srb);
> > -		desc->context.data = sg_virt(&sg[0]);
> > -		desc->context.data_length = sg[0].length;
> > +		desc->context.curr_sg = scsi_sglist(srb);
> > +		desc->context.data = sg_virt(desc->context.curr_sg);
> > +		desc->context.data_length = desc->context.curr_sg->length;
> >  	}
> >  
> 
> Would it not be better to initialize desc->context.curr_sg in both 
> branches of this conditional?

I think either way is fine given desc->context.curr_sg is used only
if 'context->data' isn't NULL, see mts_command_done().

So I'd keep the patch as it is.

Thanks,
Ming

[PATCH V3 08/15] staging: unisys: visorhba: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Cc: devel@driverdev.osuosl.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/staging/unisys/visorhba/visorhba_main.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/unisys/visorhba/visorhba_main.c b/drivers/staging/unisys/visorhba/visorhba_main.c
index 2dad36a05518..dd979ee4dcf1 100644
--- a/drivers/staging/unisys/visorhba/visorhba_main.c
+++ b/drivers/staging/unisys/visorhba/visorhba_main.c
@@ -871,12 +871,11 @@ static void do_scsi_nolinuxstat(struct uiscmdrsp *cmdrsp,
 			return;
 		}
 
-		sg = scsi_sglist(scsicmd);
-		for (i = 0; i < scsi_sg_count(scsicmd); i++) {
-			this_page_orig = kmap_atomic(sg_page(sg + i));
+		scsi_for_each_sg(scsicmd, sg, scsi_sg_count(scsicmd), i) {
+			this_page_orig = kmap_atomic(sg_page(sg));
 			this_page = (void *)((unsigned long)this_page_orig |
-					     sg[i].offset);
-			memcpy(this_page, buf + bufind, sg[i].length);
+					     sg->offset);
+			memcpy(this_page, buf + bufind, sg->length);
 			kunmap_atomic(this_page_orig);
 		}
 		kfree(buf);
-- 
2.20.1

Re: [PATCH V3 08/15] staging: unisys: visorhba: use sg helper to operate scatterlist

[Greg Kroah-Hartman]

On Fri, Jun 14, 2019 at 10:53:09AM +0800, Ming Lei wrote:
> Use the scatterlist iterators and remove direct indexing of the
> scatterlist array.
> 
> This way allows us to pre-allocate one small scatterlist, which can be
> chained with one runtime allocated scatterlist if the pre-allocated one
> isn't enough for the whole request.
> 
> Cc: devel@driverdev.osuosl.org
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/staging/unisys/visorhba/visorhba_main.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[PATCH V3 09/15] s390: zfcp_fc: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Cc: Steffen Maier <maier@linux.ibm.com>
Cc: Benjamin Block <bblock@linux.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/s390/scsi/zfcp_fc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/scsi/zfcp_fc.c b/drivers/s390/scsi/zfcp_fc.c
index 33eddb02ee30..b018b61bd168 100644
--- a/drivers/s390/scsi/zfcp_fc.c
+++ b/drivers/s390/scsi/zfcp_fc.c
@@ -620,7 +620,7 @@ static void zfcp_fc_sg_free_table(struct scatterlist *sg, int count)
 {
 	int i;
 
-	for (i = 0; i < count; i++, sg++)
+	for (i = 0; i < count; i++, sg = sg_next(sg))
 		if (sg)
 			free_page((unsigned long) sg_virt(sg));
 		else
@@ -641,7 +641,7 @@ static int zfcp_fc_sg_setup_table(struct scatterlist *sg, int count)
 	int i;
 
 	sg_init_table(sg, count);
-	for (i = 0; i < count; i++, sg++) {
+	for (i = 0; i < count; i++, sg = sg_next(sg)) {
 		addr = (void *) get_zeroed_page(GFP_KERNEL);
 		if (!addr) {
 			zfcp_fc_sg_free_table(sg, i);
-- 
2.20.1

Re: [PATCH V3 09/15] s390: zfcp_fc: use sg helper to operate scatterlist

[Benjamin Block]

On Fri, Jun 14, 2019 at 10:53:10AM +0800, Ming Lei wrote:
> Use the scatterlist iterators and remove direct indexing of the
> scatterlist array.
> 
> This way allows us to pre-allocate one small scatterlist, which can be
> chained with one runtime allocated scatterlist if the pre-allocated one
> isn't enough for the whole request.
> 
> Cc: Steffen Maier <maier@linux.ibm.com>
> Cc: Benjamin Block <bblock@linux.ibm.com>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: linux-s390@vger.kernel.org
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/s390/scsi/zfcp_fc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/s390/scsi/zfcp_fc.c b/drivers/s390/scsi/zfcp_fc.c
> index 33eddb02ee30..b018b61bd168 100644
> --- a/drivers/s390/scsi/zfcp_fc.c
> +++ b/drivers/s390/scsi/zfcp_fc.c
> @@ -620,7 +620,7 @@ static void zfcp_fc_sg_free_table(struct scatterlist *sg, int count)
>  {
>  	int i;
>  
> -	for (i = 0; i < count; i++, sg++)
> +	for (i = 0; i < count; i++, sg = sg_next(sg))
>  		if (sg)
>  			free_page((unsigned long) sg_virt(sg));
>  		else
> @@ -641,7 +641,7 @@ static int zfcp_fc_sg_setup_table(struct scatterlist *sg, int count)
>  	int i;
>  
>  	sg_init_table(sg, count);
> -	for (i = 0; i < count; i++, sg++) {
> +	for (i = 0; i < count; i++, sg = sg_next(sg)) {
>  		addr = (void *) get_zeroed_page(GFP_KERNEL);
>  		if (!addr) {
>  			zfcp_fc_sg_free_table(sg, i);

Acked-by: Benjamin Block <bblock@linux.ibm.com>

-- 
With Best Regards, Benjamin Block      /      Linux on IBM Z Kernel Development
IBM Systems & Technology Group   /  IBM Deutschland Research & Development GmbH
Vorsitz. AufsR.: Matthias Hartmann       /      Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen / Registergericht: AmtsG Stuttgart, HRB 243294

[PATCH V3 10/15] scsi: aha152x: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/aha152x.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
index 97872838b983..bc9d12aa7880 100644
--- a/drivers/scsi/aha152x.c
+++ b/drivers/scsi/aha152x.c
@@ -2033,7 +2033,7 @@ static void datai_run(struct Scsi_Host *shpnt)
 				    CURRENT_SC->SCp.buffers_residual > 0) {
 					/* advance to next buffer */
 					CURRENT_SC->SCp.buffers_residual--;
-					CURRENT_SC->SCp.buffer++;
+					CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
 					CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
 					CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
 				}
@@ -2139,7 +2139,7 @@ static void datao_run(struct Scsi_Host *shpnt)
 		if(CURRENT_SC->SCp.this_residual==0 && CURRENT_SC->SCp.buffers_residual>0) {
 			/* advance to next buffer */
 			CURRENT_SC->SCp.buffers_residual--;
-			CURRENT_SC->SCp.buffer++;
+			CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
 			CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
 			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
 		}
@@ -2160,20 +2160,29 @@ static void datao_end(struct Scsi_Host *shpnt)
 	if(TESTLO(DMASTAT, DFIFOEMP)) {
 		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
 			GETSTCNT();
+		struct scatterlist *sg = scsi_sglist(CURRENT_SC);
+		int left, i = 0;
 
 		CMD_INC_RESID(CURRENT_SC, data_count);
 
 		data_count -= CURRENT_SC->SCp.ptr -
 			SG_ADDRESS(CURRENT_SC->SCp.buffer);
-		while(data_count>0) {
-			CURRENT_SC->SCp.buffer--;
-			CURRENT_SC->SCp.buffers_residual++;
-			data_count -= CURRENT_SC->SCp.buffer->length;
+
+		left = CURRENT_SC->transfersize - data_count;
+		for (i = 0; left > 0 && !sg_is_last(sg); i++, sg = sg_next(sg)) {
+			if (left < sg->length)
+				break;
+			left -= sg->length;
+		}
+
+		if (data_count > 0) {
+			CURRENT_SC->SCp.buffers_residual += i;
+			CURRENT_SC->SCp.buffer = sg;
+
+			CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) + left;
+			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length -
+				left;
 		}
-		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
-			data_count;
-		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
-			data_count;
 	}
 
 	SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
-- 
2.20.1

Re: [PATCH V3 10/15] scsi: aha152x: use sg helper to operate scatterlist

[Finn Thain]

Hi Ming,

On Fri, 14 Jun 2019, Ming Lei wrote:

> Use the scatterlist iterators and remove direct indexing of the
> scatterlist array.
> 
> This way allows us to pre-allocate one small scatterlist, which can be
> chained with one runtime allocated scatterlist if the pre-allocated one
> isn't enough for the whole request.
> 
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/scsi/aha152x.c | 29 +++++++++++++++++++----------
>  1 file changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
> index 97872838b983..bc9d12aa7880 100644
> --- a/drivers/scsi/aha152x.c
> +++ b/drivers/scsi/aha152x.c
> @@ -2033,7 +2033,7 @@ static void datai_run(struct Scsi_Host *shpnt)
>  				    CURRENT_SC->SCp.buffers_residual > 0) {
>  					/* advance to next buffer */
>  					CURRENT_SC->SCp.buffers_residual--;
> -					CURRENT_SC->SCp.buffer++;
> +					CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
>  					CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
>  					CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
>  				}
> @@ -2139,7 +2139,7 @@ static void datao_run(struct Scsi_Host *shpnt)
>  		if(CURRENT_SC->SCp.this_residual==0 && CURRENT_SC->SCp.buffers_residual>0) {
>  			/* advance to next buffer */
>  			CURRENT_SC->SCp.buffers_residual--;
> -			CURRENT_SC->SCp.buffer++;
> +			CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
>  			CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
>  			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
>  		}
> @@ -2160,20 +2160,29 @@ static void datao_end(struct Scsi_Host *shpnt)
>  	if(TESTLO(DMASTAT, DFIFOEMP)) {
>  		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
>  			GETSTCNT();

data_count appears to be the number of bytes remaining in the FIFO. (I 
have to infer that much from the surrounding code. I don't have 
documentation for this controller.)

Some comments would be nice.

> +		struct scatterlist *sg = scsi_sglist(CURRENT_SC);
> +		int left, i = 0;
>  
>  		CMD_INC_RESID(CURRENT_SC, data_count);
>  

Apparently the aim is to increase the residual by the number of bytes that 
will never leave the FIFO. Above we can see that increase performed by 
scsi_set_resid() and now the same has to be done to the SCp struct.

>  		data_count -= CURRENT_SC->SCp.ptr -
>  			SG_ADDRESS(CURRENT_SC->SCp.buffer);

Here, data_count effectively has SCp.this_residual subtracted from it.

> -		while(data_count>0) {
> -			CURRENT_SC->SCp.buffer--;
> -			CURRENT_SC->SCp.buffers_residual++;
> -			data_count -= CURRENT_SC->SCp.buffer->length;
> -		}

So far, so good.

> -		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
> -			data_count;
> -		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
> -			data_count;

This is like saying ptr = buffer + residual, which is bogus. This must be 
an old bug, but we never hit it because the FIFO is always empty when we 
get a DISCONNECT message. Probably because every SG segment has a length 
that is a multiple of 128 bytes. (Juergen?)

> +
> +		left = CURRENT_SC->transfersize - data_count;

Are you sure about that? Perhaps you meant to write,
		left = scsi_bufflen(CURRENT_SC) - scsi_get_resid(CURRENT_SC);

Is there a better name for this variable? Maybe 'sent' or 'bytes_sent'?

> +		for (i = 0; left > 0 && !sg_is_last(sg); i++, sg = sg_next(sg)) {
> +			if (left < sg->length)
> +				break;
> +			left -= sg->length;
> +		}
> +
> +		if (data_count > 0) {
> +			CURRENT_SC->SCp.buffers_residual += i;

Shouldn't that be,
			CURRENT_SC->SCp.buffers_residual = i;

> +			CURRENT_SC->SCp.buffer = sg;
> +
> +			CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) + left;
> +			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length -
> +				left;
> +		}
>  	}
>  
>  	SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
> 

BTW, datao_run() seems to guarantee that the FIFO will never contain more 
than min(128, SCp.this_residual) so I suspect that this code can be 
simplified. That's just BTW. I wouldn't attempt to optimize this branch as 
it will only run when the FIFO is not empty, if ever. So I'd prefer 
clarity. Besides, I don't have the hardware to test it on.

-- 

Re: [PATCH V3 10/15] scsi: aha152x: use sg helper to operate scatterlist

[Ming Lei]

On Fri, Jun 14, 2019 at 03:27:36PM +1000, Finn Thain wrote:
> Hi Ming,
> 
> On Fri, 14 Jun 2019, Ming Lei wrote:
> 
> > Use the scatterlist iterators and remove direct indexing of the
> > scatterlist array.
> > 
> > This way allows us to pre-allocate one small scatterlist, which can be
> > chained with one runtime allocated scatterlist if the pre-allocated one
> > isn't enough for the whole request.
> > 
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> >  drivers/scsi/aha152x.c | 29 +++++++++++++++++++----------
> >  1 file changed, 19 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
> > index 97872838b983..bc9d12aa7880 100644
> > --- a/drivers/scsi/aha152x.c
> > +++ b/drivers/scsi/aha152x.c
> > @@ -2033,7 +2033,7 @@ static void datai_run(struct Scsi_Host *shpnt)
> >  				    CURRENT_SC->SCp.buffers_residual > 0) {
> >  					/* advance to next buffer */
> >  					CURRENT_SC->SCp.buffers_residual--;
> > -					CURRENT_SC->SCp.buffer++;
> > +					CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
> >  					CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
> >  					CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
> >  				}
> > @@ -2139,7 +2139,7 @@ static void datao_run(struct Scsi_Host *shpnt)
> >  		if(CURRENT_SC->SCp.this_residual==0 && CURRENT_SC->SCp.buffers_residual>0) {
> >  			/* advance to next buffer */
> >  			CURRENT_SC->SCp.buffers_residual--;
> > -			CURRENT_SC->SCp.buffer++;
> > +			CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
> >  			CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
> >  			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
> >  		}
> > @@ -2160,20 +2160,29 @@ static void datao_end(struct Scsi_Host *shpnt)
> >  	if(TESTLO(DMASTAT, DFIFOEMP)) {
> >  		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
> >  			GETSTCNT();
> 
> data_count appears to be the number of bytes remaining in the FIFO. (I 
> have to infer that much from the surrounding code. I don't have 
> documentation for this controller.)

Yeah, it should be so, that is the data which need to transfer again.

> 
> Some comments would be nice.
> 
> > +		struct scatterlist *sg = scsi_sglist(CURRENT_SC);
> > +		int left, i = 0;
> >  
> >  		CMD_INC_RESID(CURRENT_SC, data_count);
> >  
> 
> Apparently the aim is to increase the residual by the number of bytes that 
> will never leave the FIFO. Above we can see that increase performed by 
> scsi_set_resid() and now the same has to be done to the SCp struct.

Agree.

> 
> >  		data_count -= CURRENT_SC->SCp.ptr -
> >  			SG_ADDRESS(CURRENT_SC->SCp.buffer);
> 
> Here, data_count effectively has SCp.this_residual subtracted from it.
> 
> > -		while(data_count>0) {
> > -			CURRENT_SC->SCp.buffer--;
> > -			CURRENT_SC->SCp.buffers_residual++;
> > -			data_count -= CURRENT_SC->SCp.buffer->length;
> > -		}
> 
> So far, so good.
> 
> > -		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
> > -			data_count;
> > -		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
> > -			data_count;
> 
> This is like saying ptr = buffer + residual, which is bogus. This must be 
> an old bug, but we never hit it because the FIFO is always empty when we 
> get a DISCONNECT message. Probably because every SG segment has a length 
> that is a multiple of 128 bytes. (Juergen?)
> 
> > +
> > +		left = CURRENT_SC->transfersize - data_count;
> 
> Are you sure about that? Perhaps you meant to write,
> 		left = scsi_bufflen(CURRENT_SC) - scsi_get_resid(CURRENT_SC);
> 
> Is there a better name for this variable? Maybe 'sent' or 'bytes_sent'?

'left' can be renamed as 'done', and

	done =  GETSTCNT - (CURRENT_SC->SCp.ptr - SG_ADDRESS(CURRENT_SC->SCp.buffer))

> 
> > +		for (i = 0; left > 0 && !sg_is_last(sg); i++, sg = sg_next(sg)) {
> > +			if (left < sg->length)
> > +				break;
> > +			left -= sg->length;
> > +		}
> > +
> > +		if (data_count > 0) {
> > +			CURRENT_SC->SCp.buffers_residual += i;
> 
> Shouldn't that be,
> 			CURRENT_SC->SCp.buffers_residual = i;

Good catch.

> 
> > +			CURRENT_SC->SCp.buffer = sg;
> > +
> > +			CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) + left;
> > +			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length -
> > +				left;
> > +		}
> >  	}
> >  
> >  	SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
> > 
> 
> BTW, datao_run() seems to guarantee that the FIFO will never contain more 
> than min(128, SCp.this_residual) so I suspect that this code can be 
> simplified. That's just BTW. I wouldn't attempt to optimize this branch as 
> it will only run when the FIFO is not empty, if ever. So I'd prefer 
> clarity. Besides, I don't have the hardware to test it on.

I'd suggest to simply translate into code which uses current sg helper.

Follows the fixed version, could you review again?

From f03484d4bac083c39d70665cfbadb641093b63de Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Wed, 12 Jun 2019 20:37:35 +0800
Subject: [PATCH] scsi: aha152x: use sg helper to operate scatterlist

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/aha152x.c | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
index 97872838b983..7faecdefda56 100644
--- a/drivers/scsi/aha152x.c
+++ b/drivers/scsi/aha152x.c
@@ -2033,7 +2033,7 @@ static void datai_run(struct Scsi_Host *shpnt)
 				    CURRENT_SC->SCp.buffers_residual > 0) {
 					/* advance to next buffer */
 					CURRENT_SC->SCp.buffers_residual--;
-					CURRENT_SC->SCp.buffer++;
+					CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
 					CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
 					CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
 				}
@@ -2139,7 +2139,7 @@ static void datao_run(struct Scsi_Host *shpnt)
 		if(CURRENT_SC->SCp.this_residual==0 && CURRENT_SC->SCp.buffers_residual>0) {
 			/* advance to next buffer */
 			CURRENT_SC->SCp.buffers_residual--;
-			CURRENT_SC->SCp.buffer++;
+			CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
 			CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
 			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
 		}
@@ -2158,22 +2158,28 @@ static void datao_run(struct Scsi_Host *shpnt)
 static void datao_end(struct Scsi_Host *shpnt)
 {
 	if(TESTLO(DMASTAT, DFIFOEMP)) {
-		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
-			GETSTCNT();
+		int done = GETSTCNT();
+		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) - done;
+		struct scatterlist *sg = scsi_sglist(CURRENT_SC);
+		int i;
 
 		CMD_INC_RESID(CURRENT_SC, data_count);
 
-		data_count -= CURRENT_SC->SCp.ptr -
-			SG_ADDRESS(CURRENT_SC->SCp.buffer);
-		while(data_count>0) {
-			CURRENT_SC->SCp.buffer--;
-			CURRENT_SC->SCp.buffers_residual++;
-			data_count -= CURRENT_SC->SCp.buffer->length;
+		/*
+		 * rewind where we have done, and we have to start from
+		 * the beginning
+		 */
+		for (i = 0; done > 0 && !sg_is_last(sg); i++, sg = sg_next(sg)) {
+			if (done < sg->length)
+				break;
+			done -= sg->length;
 		}
-		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
-			data_count;
-		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
-			data_count;
+
+		CURRENT_SC->SCp.buffers_residual = i;
+		CURRENT_SC->SCp.buffer = sg;
+		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) + done;
+		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length -
+			done;
 	}
 
 	SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
-- 
2.20.1


thanks,
Ming

Re: [PATCH V3 10/15] scsi: aha152x: use sg helper to operate scatterlist

[Finn Thain]

On Fri, 14 Jun 2019, Ming Lei wrote:

> 
> Follows the fixed version, could you review again?
> 
> From f03484d4bac083c39d70665cfbadb641093b63de Mon Sep 17 00:00:00 2001
> From: Ming Lei <ming.lei@redhat.com>
> Date: Wed, 12 Jun 2019 20:37:35 +0800
> Subject: [PATCH] scsi: aha152x: use sg helper to operate scatterlist
> 
> Use the scatterlist iterators and remove direct indexing of the
> scatterlist array.
> 
> This way allows us to pre-allocate one small scatterlist, which can be
> chained with one runtime allocated scatterlist if the pre-allocated one
> isn't enough for the whole request.
> 
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/scsi/aha152x.c | 34 ++++++++++++++++++++--------------
>  1 file changed, 20 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
> index 97872838b983..7faecdefda56 100644
> --- a/drivers/scsi/aha152x.c
> +++ b/drivers/scsi/aha152x.c
> @@ -2033,7 +2033,7 @@ static void datai_run(struct Scsi_Host *shpnt)
>  				    CURRENT_SC->SCp.buffers_residual > 0) {
>  					/* advance to next buffer */
>  					CURRENT_SC->SCp.buffers_residual--;
> -					CURRENT_SC->SCp.buffer++;
> +					CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
>  					CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
>  					CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
>  				}
> @@ -2139,7 +2139,7 @@ static void datao_run(struct Scsi_Host *shpnt)
>  		if(CURRENT_SC->SCp.this_residual==0 && CURRENT_SC->SCp.buffers_residual>0) {
>  			/* advance to next buffer */
>  			CURRENT_SC->SCp.buffers_residual--;
> -			CURRENT_SC->SCp.buffer++;
> +			CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
>  			CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
>  			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
>  		}
> @@ -2158,22 +2158,28 @@ static void datao_run(struct Scsi_Host *shpnt)
>  static void datao_end(struct Scsi_Host *shpnt)
>  {
>  	if(TESTLO(DMASTAT, DFIFOEMP)) {
> -		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
> -			GETSTCNT();
> +		int done = GETSTCNT();
> +		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) - done;

I think that's better than my suggestion.

> +		struct scatterlist *sg = scsi_sglist(CURRENT_SC);
> +		int i;
>  
>  		CMD_INC_RESID(CURRENT_SC, data_count);
>  
> -		data_count -= CURRENT_SC->SCp.ptr -
> -			SG_ADDRESS(CURRENT_SC->SCp.buffer);
> -		while(data_count>0) {
> -			CURRENT_SC->SCp.buffer--;
> -			CURRENT_SC->SCp.buffers_residual++;
> -			data_count -= CURRENT_SC->SCp.buffer->length;
> +		/*
> +		 * rewind where we have done, and we have to start from
> +		 * the beginning
> +		 */

How about, "Locate the first SG entry not yet sent".

We could use sg_nents_for_len() but it returns a count of sg entries not a 
scatterlist pointer so it's not very helpful here.

> +		for (i = 0; done > 0 && !sg_is_last(sg); i++, sg = sg_next(sg)) {
> +			if (done < sg->length)
> +				break;
> +			done -= sg->length;
>  		}
> -		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
> -			data_count;
> -		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
> -			data_count;
> +
> +		CURRENT_SC->SCp.buffers_residual = i;

Contradicting my previous email, that's still not right. I think it would 
have to be,

		CURRENT_SC->SCp.buffers_residual = scsi_sg_count(CURRENT_SC) - i;

But we could remove all references to SCp.buffers_residual, like I did in 
patch 15/15 for NCR5380.c.

> +		CURRENT_SC->SCp.buffer = sg;
> +		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) + done;
> +		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length -
> +			done;
>  	}
>  
>  	SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
> 

What do you think of the revised patch below?

diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
index 97872838b983..6d0518f616cb 100644
--- a/drivers/scsi/aha152x.c
+++ b/drivers/scsi/aha152x.c
@@ -948,7 +948,6 @@ static int aha152x_internal_queue(struct scsi_cmnd *SCpnt,
 	   SCp.ptr              : buffer pointer
 	   SCp.this_residual    : buffer length
 	   SCp.buffer           : next buffer
-	   SCp.buffers_residual : left buffers in list
 	   SCp.phase            : current state of the command */
 
 	if ((phase & resetting) || !scsi_sglist(SCpnt)) {
@@ -956,13 +955,11 @@ static int aha152x_internal_queue(struct scsi_cmnd *SCpnt,
 		SCpnt->SCp.this_residual = 0;
 		scsi_set_resid(SCpnt, 0);
 		SCpnt->SCp.buffer           = NULL;
-		SCpnt->SCp.buffers_residual = 0;
 	} else {
 		scsi_set_resid(SCpnt, scsi_bufflen(SCpnt));
 		SCpnt->SCp.buffer           = scsi_sglist(SCpnt);
 		SCpnt->SCp.ptr              = SG_ADDRESS(SCpnt->SCp.buffer);
 		SCpnt->SCp.this_residual    = SCpnt->SCp.buffer->length;
-		SCpnt->SCp.buffers_residual = scsi_sg_count(SCpnt) - 1;
 	}
 
 	DO_LOCK(flags);
@@ -2030,10 +2027,9 @@ static void datai_run(struct Scsi_Host *shpnt)
 				}
 
 				if (CURRENT_SC->SCp.this_residual == 0 &&
-				    CURRENT_SC->SCp.buffers_residual > 0) {
+				    !sg_is_last(CURRENT_SC->SCp.buffer)) {
 					/* advance to next buffer */
-					CURRENT_SC->SCp.buffers_residual--;
-					CURRENT_SC->SCp.buffer++;
+					CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
 					CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
 					CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
 				}
@@ -2136,10 +2132,10 @@ static void datao_run(struct Scsi_Host *shpnt)
 			CMD_INC_RESID(CURRENT_SC, -2 * data_count);
 		}
 
-		if(CURRENT_SC->SCp.this_residual==0 && CURRENT_SC->SCp.buffers_residual>0) {
+		if(CURRENT_SC->SCp.this_residual==0 &&
+		   !sg_is_last(CURRENT_SC->SCp.buffer)) {
 			/* advance to next buffer */
-			CURRENT_SC->SCp.buffers_residual--;
-			CURRENT_SC->SCp.buffer++;
+			CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
 			CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
 			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
 		}
@@ -2158,22 +2154,24 @@ static void datao_run(struct Scsi_Host *shpnt)
 static void datao_end(struct Scsi_Host *shpnt)
 {
 	if(TESTLO(DMASTAT, DFIFOEMP)) {
-		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
-			GETSTCNT();
+		int done = GETSTCNT();
+		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) - done;
+		struct scatterlist *sg = scsi_sglist(CURRENT_SC);
 
 		CMD_INC_RESID(CURRENT_SC, data_count);
 
-		data_count -= CURRENT_SC->SCp.ptr -
-			SG_ADDRESS(CURRENT_SC->SCp.buffer);
-		while(data_count>0) {
-			CURRENT_SC->SCp.buffer--;
-			CURRENT_SC->SCp.buffers_residual++;
-			data_count -= CURRENT_SC->SCp.buffer->length;
+		/* Locate the first SG entry not yet sent */
+		while (done > 0 && !sg_is_last(sg)) {
+			if (done < sg->length)
+				break;
+			done -= sg->length;
+			sg = sg_next(sg);
 		}
-		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
-			data_count;
-		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
-			data_count;
+
+		CURRENT_SC->SCp.buffer = sg;
+		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) + done;
+		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length -
+			done;
 	}
 
 	SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
@@ -2501,7 +2499,7 @@ static void get_command(struct seq_file *m, struct scsi_cmnd * ptr)
 
 	seq_printf(m, "); resid=%d; residual=%d; buffers=%d; phase |",
 		scsi_get_resid(ptr), ptr->SCp.this_residual,
-		ptr->SCp.buffers_residual);
+		sg_nents(ptr->SCp.buffer) - 1);
 
 	if (ptr->SCp.phase & not_issued)
 		seq_puts(m, "not issued|");

-- 

Re: [PATCH V3 10/15] scsi: aha152x: use sg helper to operate scatterlist

[Ming Lei]

On Fri, Jun 14, 2019 at 08:36:38PM +1000, Finn Thain wrote:
> On Fri, 14 Jun 2019, Ming Lei wrote:
> 
> > 
> > Follows the fixed version, could you review again?
> > 
> > From f03484d4bac083c39d70665cfbadb641093b63de Mon Sep 17 00:00:00 2001
> > From: Ming Lei <ming.lei@redhat.com>
> > Date: Wed, 12 Jun 2019 20:37:35 +0800
> > Subject: [PATCH] scsi: aha152x: use sg helper to operate scatterlist
> > 
> > Use the scatterlist iterators and remove direct indexing of the
> > scatterlist array.
> > 
> > This way allows us to pre-allocate one small scatterlist, which can be
> > chained with one runtime allocated scatterlist if the pre-allocated one
> > isn't enough for the whole request.
> > 
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> >  drivers/scsi/aha152x.c | 34 ++++++++++++++++++++--------------
> >  1 file changed, 20 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
> > index 97872838b983..7faecdefda56 100644
> > --- a/drivers/scsi/aha152x.c
> > +++ b/drivers/scsi/aha152x.c
> > @@ -2033,7 +2033,7 @@ static void datai_run(struct Scsi_Host *shpnt)
> >  				    CURRENT_SC->SCp.buffers_residual > 0) {
> >  					/* advance to next buffer */
> >  					CURRENT_SC->SCp.buffers_residual--;
> > -					CURRENT_SC->SCp.buffer++;
> > +					CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
> >  					CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
> >  					CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
> >  				}
> > @@ -2139,7 +2139,7 @@ static void datao_run(struct Scsi_Host *shpnt)
> >  		if(CURRENT_SC->SCp.this_residual==0 && CURRENT_SC->SCp.buffers_residual>0) {
> >  			/* advance to next buffer */
> >  			CURRENT_SC->SCp.buffers_residual--;
> > -			CURRENT_SC->SCp.buffer++;
> > +			CURRENT_SC->SCp.buffer = sg_next(CURRENT_SC->SCp.buffer);
> >  			CURRENT_SC->SCp.ptr           = SG_ADDRESS(CURRENT_SC->SCp.buffer);
> >  			CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length;
> >  		}
> > @@ -2158,22 +2158,28 @@ static void datao_run(struct Scsi_Host *shpnt)
> >  static void datao_end(struct Scsi_Host *shpnt)
> >  {
> >  	if(TESTLO(DMASTAT, DFIFOEMP)) {
> > -		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
> > -			GETSTCNT();
> > +		int done = GETSTCNT();
> > +		int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) - done;
> 
> I think that's better than my suggestion.
> 
> > +		struct scatterlist *sg = scsi_sglist(CURRENT_SC);
> > +		int i;
> >  
> >  		CMD_INC_RESID(CURRENT_SC, data_count);
> >  
> > -		data_count -= CURRENT_SC->SCp.ptr -
> > -			SG_ADDRESS(CURRENT_SC->SCp.buffer);
> > -		while(data_count>0) {
> > -			CURRENT_SC->SCp.buffer--;
> > -			CURRENT_SC->SCp.buffers_residual++;
> > -			data_count -= CURRENT_SC->SCp.buffer->length;
> > +		/*
> > +		 * rewind where we have done, and we have to start from
> > +		 * the beginning
> > +		 */
> 
> How about, "Locate the first SG entry not yet sent".

OK.

> 
> We could use sg_nents_for_len() but it returns a count of sg entries not a 
> scatterlist pointer so it's not very helpful here.
> 
> > +		for (i = 0; done > 0 && !sg_is_last(sg); i++, sg = sg_next(sg)) {
> > +			if (done < sg->length)
> > +				break;
> > +			done -= sg->length;
> >  		}
> > -		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
> > -			data_count;
> > -		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
> > -			data_count;
> > +
> > +		CURRENT_SC->SCp.buffers_residual = i;
> 
> Contradicting my previous email, that's still not right. I think it would 
> have to be,
> 
> 		CURRENT_SC->SCp.buffers_residual = scsi_sg_count(CURRENT_SC) - i;

Right, my fault.

> 
> But we could remove all references to SCp.buffers_residual, like I did in 
> patch 15/15 for NCR5380.c.
> 
> > +		CURRENT_SC->SCp.buffer = sg;
> > +		CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) + done;
> > +		CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length -
> > +			done;
> >  	}
> >  
> >  	SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
> > 
> 
> What do you think of the revised patch below?

Looks fine, I will include it in V4.

Thanks,
Ming

[PATCH V3 11/15] scsi: imm: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/imm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/imm.c b/drivers/scsi/imm.c
index 64ae418d29f3..56d29f157749 100644
--- a/drivers/scsi/imm.c
+++ b/drivers/scsi/imm.c
@@ -686,7 +686,7 @@ static int imm_completion(struct scsi_cmnd *cmd)
 		if (cmd->SCp.buffer && !cmd->SCp.this_residual) {
 			/* if scatter/gather, advance to the next segment */
 			if (cmd->SCp.buffers_residual--) {
-				cmd->SCp.buffer++;
+				cmd->SCp.buffer = sg_next(cmd->SCp.buffer);
 				cmd->SCp.this_residual =
 				    cmd->SCp.buffer->length;
 				cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-- 
2.20.1

[PATCH V3 12/15] scsi: pcmcia: nsp_cs: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/pcmcia/nsp_cs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/pcmcia/nsp_cs.c b/drivers/scsi/pcmcia/nsp_cs.c
index a81748e6e8fb..97416e1dcc5b 100644
--- a/drivers/scsi/pcmcia/nsp_cs.c
+++ b/drivers/scsi/pcmcia/nsp_cs.c
@@ -789,7 +789,7 @@ static void nsp_pio_read(struct scsi_cmnd *SCpnt)
 		    SCpnt->SCp.buffers_residual != 0 ) {
 			//nsp_dbg(NSP_DEBUG_DATA_IO, "scatterlist next timeout=%d", time_out);
 			SCpnt->SCp.buffers_residual--;
-			SCpnt->SCp.buffer++;
+			SCpnt->SCp.buffer = sg_next(SCpnt->SCp.buffer);
 			SCpnt->SCp.ptr		 = BUFFER_ADDR;
 			SCpnt->SCp.this_residual = SCpnt->SCp.buffer->length;
 			time_out = 1000;
@@ -887,7 +887,7 @@ static void nsp_pio_write(struct scsi_cmnd *SCpnt)
 		    SCpnt->SCp.buffers_residual != 0 ) {
 			//nsp_dbg(NSP_DEBUG_DATA_IO, "scatterlist next");
 			SCpnt->SCp.buffers_residual--;
-			SCpnt->SCp.buffer++;
+			SCpnt->SCp.buffer = sg_next(SCpnt->SCp.buffer);
 			SCpnt->SCp.ptr		 = BUFFER_ADDR;
 			SCpnt->SCp.this_residual = SCpnt->SCp.buffer->length;
 			time_out = 1000;
-- 
2.20.1

[PATCH V3 13/15] scsi: ppa: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/ppa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/ppa.c b/drivers/scsi/ppa.c
index 35213082e933..a406cc825426 100644
--- a/drivers/scsi/ppa.c
+++ b/drivers/scsi/ppa.c
@@ -590,7 +590,7 @@ static int ppa_completion(struct scsi_cmnd *cmd)
 		if (cmd->SCp.buffer && !cmd->SCp.this_residual) {
 			/* if scatter/gather, advance to the next segment */
 			if (cmd->SCp.buffers_residual--) {
-				cmd->SCp.buffer++;
+				cmd->SCp.buffer = sg_next(cmd->SCp.buffer);
 				cmd->SCp.this_residual =
 				    cmd->SCp.buffer->length;
 				cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-- 
2.20.1

[PATCH V3 14/15] scsi: wd33c93: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/wd33c93.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/wd33c93.c b/drivers/scsi/wd33c93.c
index 74be04f2357c..ae5935c0a149 100644
--- a/drivers/scsi/wd33c93.c
+++ b/drivers/scsi/wd33c93.c
@@ -744,7 +744,7 @@ transfer_bytes(const wd33c93_regs regs, struct scsi_cmnd *cmd,
  * source or destination for THIS transfer.
  */
 	if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) {
-		++cmd->SCp.buffer;
+		cmd->SCp.buffer = sg_next(cmd->SCp.buffer);
 		--cmd->SCp.buffers_residual;
 		cmd->SCp.this_residual = cmd->SCp.buffer->length;
 		cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-- 
2.20.1

[PATCH V3 15/15] NCR5380: Support chained sg lists

[Ming Lei]

From: Finn Thain <fthain@telegraphics.com.au>

My understanding is that support for chained scatterlists is to
become mandatory for LLDs.

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Cc: Michael Schmitz <schmitzmic@gmail.com>
Reviewed-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 drivers/scsi/NCR5380.c | 41 ++++++++++++++++++-----------------------
 1 file changed, 18 insertions(+), 23 deletions(-)

diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
index fe0535affc14..4ef44fafe6ca 100644
--- a/drivers/scsi/NCR5380.c
+++ b/drivers/scsi/NCR5380.c
@@ -149,12 +149,10 @@ static inline void initialize_SCp(struct scsi_cmnd *cmd)
 
 	if (scsi_bufflen(cmd)) {
 		cmd->SCp.buffer = scsi_sglist(cmd);
-		cmd->SCp.buffers_residual = scsi_sg_count(cmd) - 1;
 		cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
 		cmd->SCp.this_residual = cmd->SCp.buffer->length;
 	} else {
 		cmd->SCp.buffer = NULL;
-		cmd->SCp.buffers_residual = 0;
 		cmd->SCp.ptr = NULL;
 		cmd->SCp.this_residual = 0;
 	}
@@ -163,6 +161,17 @@ static inline void initialize_SCp(struct scsi_cmnd *cmd)
 	cmd->SCp.Message = 0;
 }
 
+static inline void advance_sg_buffer(struct scsi_cmnd *cmd)
+{
+	struct scatterlist *s = cmd->SCp.buffer;
+
+	if (!cmd->SCp.this_residual && s && !sg_is_last(s)) {
+		cmd->SCp.buffer = sg_next(s);
+		cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
+		cmd->SCp.this_residual = cmd->SCp.buffer->length;
+	}
+}
+
 /**
  * NCR5380_poll_politely2 - wait for two chip register values
  * @hostdata: host private data
@@ -1672,12 +1681,7 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance)
 			    sun3_dma_setup_done != cmd) {
 				int count;
 
-				if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) {
-					++cmd->SCp.buffer;
-					--cmd->SCp.buffers_residual;
-					cmd->SCp.this_residual = cmd->SCp.buffer->length;
-					cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-				}
+				advance_sg_buffer(cmd);
 
 				count = sun3scsi_dma_xfer_len(hostdata, cmd);
 
@@ -1727,15 +1731,11 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance)
 				 * scatter-gather list, move onto the next one.
 				 */
 
-				if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) {
-					++cmd->SCp.buffer;
-					--cmd->SCp.buffers_residual;
-					cmd->SCp.this_residual = cmd->SCp.buffer->length;
-					cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-					dsprintk(NDEBUG_INFORMATION, instance, "%d bytes and %d buffers left\n",
-					         cmd->SCp.this_residual,
-					         cmd->SCp.buffers_residual);
-				}
+				advance_sg_buffer(cmd);
+				dsprintk(NDEBUG_INFORMATION, instance,
+					"this residual %d, sg ents %d\n",
+					cmd->SCp.this_residual,
+					sg_nents(cmd->SCp.buffer));
 
 				/*
 				 * The preferred transfer method is going to be
@@ -2136,12 +2136,7 @@ static void NCR5380_reselect(struct Scsi_Host *instance)
 	if (sun3_dma_setup_done != tmp) {
 		int count;
 
-		if (!tmp->SCp.this_residual && tmp->SCp.buffers_residual) {
-			++tmp->SCp.buffer;
-			--tmp->SCp.buffers_residual;
-			tmp->SCp.this_residual = tmp->SCp.buffer->length;
-			tmp->SCp.ptr = sg_virt(tmp->SCp.buffer);
-		}
+		advance_sg_buffer(tmp);
 
 		count = sun3scsi_dma_xfer_len(hostdata, tmp);
 
-- 
2.20.1