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nvmet-fc: simplify sg list handling

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The existing nvmet_fc sg list handling has 2 faults:
a) the request between LLDD and transport has too large of an sg
   list (256 elements), which is normally 256k (64 elements).
b) sglist handling doesn't optimize on the fact that each element
   is a page.

This patch removes the static sg list in the request and uses the
dynamic list already present in the nvmet_fc transport. It also
simplies the handling of the sg list on multiple sequences to
take advantage of the per-page divisions.

Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
James Smart 2017-07-31 13:21:14 -07:00 committed by Sagi Grimberg
parent 5533d42480
commit 48fa362b6c
2 changed files with 11 additions and 39 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

48
drivers/nvme/target/fc.c
View file

@ -58,7 +58,8 @@ struct nvmet_fc_ls_iod {
struct work_struct work;
} __aligned(sizeof(unsigned long long));
#define NVMET_FC_MAX_KB_PER_XFR 256
#define NVMET_FC_MAX_SEQ_LENGTH (256 * 1024)
#define NVMET_FC_MAX_XFR_SGENTS (NVMET_FC_MAX_SEQ_LENGTH / PAGE_SIZE)
enum nvmet_fcp_datadir {
NVMET_FCP_NODATA,
@ -74,9 +75,7 @@ struct nvmet_fc_fcp_iod {
struct nvme_fc_ersp_iu rspiubuf;
dma_addr_t rspdma;
struct scatterlist *data_sg;
struct scatterlist *next_sg;
int data_sg_cnt;
u32 next_sg_offset;
u32 total_length;
u32 offset;
enum nvmet_fcp_datadir io_dir;
@ -112,6 +111,7 @@ struct nvmet_fc_tgtport {
struct ida assoc_cnt;
struct nvmet_port *port;
struct kref ref;
u32 max_sg_cnt;
};
struct nvmet_fc_defer_fcp_req {
@ -994,6 +994,8 @@ nvmet_fc_register_targetport(struct nvmet_fc_port_info *pinfo,
INIT_LIST_HEAD(&newrec->assoc_list);
kref_init(&newrec->ref);
ida_init(&newrec->assoc_cnt);
newrec->max_sg_cnt = min_t(u32, NVMET_FC_MAX_XFR_SGENTS,
template->max_sgl_segments);
ret = nvmet_fc_alloc_ls_iodlist(newrec);
if (ret) {
@ -1866,51 +1868,23 @@ nvmet_fc_transfer_fcp_data(struct nvmet_fc_tgtport *tgtport,
struct nvmet_fc_fcp_iod *fod, u8 op)
{
struct nvmefc_tgt_fcp_req *fcpreq = fod->fcpreq;
struct scatterlist *sg, *datasg;
unsigned long flags;
u32 tlen, sg_off;
u32 tlen;
int ret;
fcpreq->op = op;
fcpreq->offset = fod->offset;
fcpreq->timeout = NVME_FC_TGTOP_TIMEOUT_SEC;
tlen = min_t(u32, (NVMET_FC_MAX_KB_PER_XFR * 1024),
tlen = min_t(u32, tgtport->max_sg_cnt * PAGE_SIZE,
(fod->total_length - fod->offset));
tlen = min_t(u32, tlen, NVME_FC_MAX_SEGMENTS * PAGE_SIZE);
tlen = min_t(u32, tlen, fod->tgtport->ops->max_sgl_segments
* PAGE_SIZE);
fcpreq->transfer_length = tlen;
fcpreq->transferred_length = 0;
fcpreq->fcp_error = 0;
fcpreq->rsplen = 0;
fcpreq->sg_cnt = 0;
datasg = fod->next_sg;
sg_off = fod->next_sg_offset;
for (sg = fcpreq->sg ; tlen; sg++) {
*sg = *datasg;
if (sg_off) {
sg->offset += sg_off;
sg->length -= sg_off;
sg->dma_address += sg_off;
sg_off = 0;
}
if (tlen < sg->length) {
sg->length = tlen;
fod->next_sg = datasg;
fod->next_sg_offset += tlen;
} else if (tlen == sg->length) {
fod->next_sg_offset = 0;
fod->next_sg = sg_next(datasg);
} else {
fod->next_sg_offset = 0;
datasg = sg_next(datasg);
}
tlen -= sg->length;
fcpreq->sg_cnt++;
}
fcpreq->sg = &fod->data_sg[fod->offset / PAGE_SIZE];
fcpreq->sg_cnt = DIV_ROUND_UP(tlen, PAGE_SIZE);
/*
* If the last READDATA request: check if LLDD supports
@ -2225,8 +2199,6 @@ nvmet_fc_handle_fcp_rqst(struct nvmet_fc_tgtport *tgtport,
fod->req.sg = fod->data_sg;
fod->req.sg_cnt = fod->data_sg_cnt;
fod->offset = 0;
fod->next_sg = fod->data_sg;
fod->next_sg_offset = 0;
if (fod->io_dir == NVMET_FCP_WRITE) {
/* pull the data over before invoking nvmet layer */

2
include/linux/nvme-fc-driver.h
View file

@ -624,7 +624,7 @@ struct nvmefc_tgt_fcp_req {
u32 timeout;
u32 transfer_length;
struct fc_ba_rjt ba_rjt;
struct scatterlist sg[NVME_FC_MAX_SEGMENTS];
struct scatterlist *sg;
int sg_cnt;
void *rspaddr;
dma_addr_t rspdma;