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

Message

Ming Lei June 14, 2019, 2:53 a.m. UTC

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(-)