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From: Ming Lei <ming.lei@redhat.com>
To: linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>, Christoph Hellwig <hch@lst.de>,
	Jim Gill <jgill@vmware.com>, Cathy Avery <cavery@redhat.com>,
	"Ewan D . Milne" <emilne@redhat.com>,
	Brian King <brking@us.ibm.com>,
	James Smart <james.smart@broadcom.com>,
	"Juergen E . Fischer" <fischer@norbit.de>,
	Michael Schmitz <schmitzmic@gmail.com>,
	Finn Thain <fthain@telegraphics.com.au>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	devel@driverdev.osuosl.org, linux-usb@vger.kernel.org,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Benjamin Block <bblock@linux.ibm.com>,
	Ming Lei <ming.lei@redhat.com>
Subject: [PATCH V4 00/16] use sg helper to operate scatterlist
Date: Mon, 17 Jun 2019 11:03:33 +0800
Message-ID: <20190617030349.26415-1-ming.lei@redhat.com> (raw)

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 direct access on scatterlist in SCSI drivers:

1) operate on the scatterlist via scsi_sglist(scmd) directly, then one
local variable of 'struct scatterlist *' is involved.

2) scsi_sglist(scmd) is stored to cmd->SCp.buffer and the scatterlist is
used via cmd->SCp.buffer.

The following coccinelle semantic patch is developed for finding the
above two types of direct scatterlist uses:

	@@ struct scatterlist *p; @@
	(
	- ++p
	+ p = sg_next(p)
	|
	- p++
	+ p = sg_next(p)
	|
	- p = p + 1
	+ p = sg_next(p)
	|
	- p += 1
	+ p = sg_next(p)
	|
	- --p
	+ p = sg_non_exist_prev(p)
	|
	- p--
	+ p = sg_non_exist_prev(p)
	|
	- p = p - 1
	+ p = sg_non_exist_prev(p)
	|
	- p -= 1
	+ p = sg_non_exist_prev(p)
	)
	
	@@
	struct scatterlist *p;
	expression data != 0;
	@@
	- p[data]
	+ '!!!!!!use sg iterator helper!!!!!!'
	
	@@
	struct scatterlist[] p;
	expression data != 0;
	@@
	- p[data]
	+ '!!!!!!use sg iterator helper!!!!!!'
	
	
	@@ struct scsi_cmnd *scmd; @@
	(
	-	scmd->SCp.buffer++
	+	scmd->SCp.buffer = sg_next(scmd->SCp.buffer)
	|
	-	++scmd->SCp.buffer
	+	scmd->SCp.buffer = sg_next(scmd->SCp.buffer)
	|
	-	scmd->SCp.buffer += 1
	+	scmd->SCp.buffer = sg_next(scmd->SCp.buffer)
	|
	-	scmd->SCp.buffer = scmd->SCp.buffer + 1
	+	scmd->SCp.buffer = sg_next(scmd->SCp.buffer)
	|
	-	scmd->SCp.buffer--
	+	scmd->SCp.buffer = sg_no_exit_prev(scmd->SCp.buffer)
	|
	-	--scmd->SCp.buffer
	+	scmd->SCp.buffer = sg_no_exit_prev(scmd->SCp.buffer)
	|
	-	scmd->SCp.buffer -= 1
	+	scmd->SCp.buffer = sg_no_exit_prev(scmd->SCp.buffer)
	|
	-	scmd->SCp.buffer = scmd->SCp.buffer - 1
	+	scmd->SCp.buffer = sg_no_exit_prev(scmd->SCp.buffer)
	)
	
	@@
	struct scsi_cmnd *scmd;
	expression data != 0;
	@@
	- scmd->SCp.buffer[data]
	+ '!!!!!!use sg iterator helper!!!!!!'


The 1st 10 patches are for handling type #1, and the other 6 patches
for handling type #2, and all the 16 are found by the above coccinelle
semantic patch.

V4:
	- fix building failure on pmcraid's conversion 
	- improve the coccinelle semantic patch to cover both two types of
	scatterlist direct use
	- driver 'staging: rtsx' is covered

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 (15):
  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
  staging: rtsx: 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                        | 42 +++++++++----------
 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                        | 14 +++----
 drivers/scsi/ppa.c                            |  2 +-
 drivers/scsi/vmw_pvscsi.c                     |  2 +-
 drivers/scsi/wd33c93.c                        |  2 +-
 drivers/staging/rts5208/rtsx_transport.c      |  4 +-
 .../staging/unisys/visorhba/visorhba_main.c   |  9 ++--
 drivers/usb/image/microtek.c                  | 20 ++++-----
 drivers/usb/image/microtek.h                  |  2 +-
 17 files changed, 90 insertions(+), 100 deletions(-)

-- 
2.20.1


             reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-17  3:03 Ming Lei [this message]
2019-06-17  3:03 ` [PATCH V4 01/16] scsi: vmw_pscsi: " Ming Lei
2019-06-17  8:22   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 02/16] scsi: advansys: " Ming Lei
2019-06-17  8:22   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 03/16] scsi: lpfc: " Ming Lei
2019-06-17  8:22   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 04/16] scsi: mvumi: " Ming Lei
2019-06-17  8:22   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 05/16] scsi: ipr: " Ming Lei
2019-06-17  8:24   ` Christoph Hellwig
2019-06-17  8:50     ` Ming Lei
2019-06-17  3:03 ` [PATCH V4 06/16] scsi: pmcraid: " Ming Lei
2019-06-17  8:24   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 07/16] usb: image: microtek: " Ming Lei
2019-06-17  8:25   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 08/16] staging: unisys: visorhba: " Ming Lei
2019-06-17  8:25   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 09/16] staging: rtsx: " Ming Lei
2019-06-17  8:27   ` Christoph Hellwig
2019-06-17  9:15     ` Ming Lei
2019-06-17  9:24       ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 10/16] s390: zfcp_fc: " Ming Lei
2019-06-17  8:27   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 11/16] scsi: aha152x: " Ming Lei
2019-06-17  3:35   ` Finn Thain
2019-06-17 23:35     ` Finn Thain
2019-06-18  0:15       ` Ming Lei
2019-06-17  8:28   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 12/16] scsi: imm: " Ming Lei
2019-06-17  8:28   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 13/16] scsi: pcmcia: nsp_cs: " Ming Lei
2019-06-17  8:29   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 14/16] scsi: ppa: " Ming Lei
2019-06-17  8:29   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 15/16] scsi: wd33c93: " Ming Lei
2019-06-17  8:29   ` Christoph Hellwig
2019-06-17  3:03 ` [PATCH V4 16/16] NCR5380: Support chained sg lists Ming Lei
2019-06-17  8:30   ` Christoph Hellwig
2019-06-17 23:52 ` [PATCH V4 00/16] use sg helper to operate scatterlist Bart Van Assche

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