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
