From 426f6059b0eb66cec139f4b9066168ab72b85774 Mon Sep 17 00:00:00 2001 From: Christof Schmitt Date: Mon, 13 Jul 2009 15:06:06 +0200 Subject: [PATCH] [SCSI] zfcp: Use unchained mode for small ct and els requests The ELS ADISC and the GID_PN requests sent from zfcp fit into unchained FSF requests. Change the FSF allocation logic to use unchained requests whenever possible where everything fits in one SBAL. This avoids acquiring more SBALs than necessary, especially during zfcp recovery when things might be stalled. Reviewed-by: Swen Schillig Signed-off-by: Christof Schmitt Signed-off-by: James Bottomley --- drivers/s390/scsi/zfcp_fsf.c | 33 +++++++++++++++++++++++++-------- 1 file changed, 25 insertions(+), 8 deletions(-) diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c index c4eb62b..bec9125 100644 --- a/drivers/s390/scsi/zfcp_fsf.c +++ b/drivers/s390/scsi/zfcp_fsf.c @@ -1010,6 +1010,23 @@ skip_fsfstatus: send_ct->handler(send_ct->handler_data); } +static void zfcp_fsf_setup_ct_els_unchained(struct qdio_buffer_element *sbale, + struct scatterlist *sg_req, + struct scatterlist *sg_resp) +{ + sbale[0].flags |= SBAL_FLAGS0_TYPE_WRITE_READ; + sbale[2].addr = sg_virt(sg_req); + sbale[2].length = sg_req->length; + sbale[3].addr = sg_virt(sg_resp); + sbale[3].length = sg_resp->length; + sbale[3].flags |= SBAL_FLAGS_LAST_ENTRY; +} + +static int zfcp_fsf_one_sbal(struct scatterlist *sg) +{ + return sg_is_last(sg) && sg->length <= PAGE_SIZE; +} + static int zfcp_fsf_setup_ct_els_sbals(struct zfcp_fsf_req *req, struct scatterlist *sg_req, struct scatterlist *sg_resp, @@ -1020,16 +1037,16 @@ static int zfcp_fsf_setup_ct_els_sbals(struct zfcp_fsf_req *req, int bytes; if (!(feat & FSF_FEATURE_ELS_CT_CHAINED_SBALS)) { - if (sg_req->length > PAGE_SIZE || sg_resp->length > PAGE_SIZE || - !sg_is_last(sg_req) || !sg_is_last(sg_resp)) + if (!zfcp_fsf_one_sbal(sg_req) || !zfcp_fsf_one_sbal(sg_resp)) return -EOPNOTSUPP; - sbale[0].flags |= SBAL_FLAGS0_TYPE_WRITE_READ; - sbale[2].addr = sg_virt(sg_req); - sbale[2].length = sg_req->length; - sbale[3].addr = sg_virt(sg_resp); - sbale[3].length = sg_resp->length; - sbale[3].flags |= SBAL_FLAGS_LAST_ENTRY; + zfcp_fsf_setup_ct_els_unchained(sbale, sg_req, sg_resp); + return 0; + } + + /* use single, unchained SBAL if it can hold the request */ + if (zfcp_fsf_one_sbal(sg_req) && zfcp_fsf_one_sbal(sg_resp)) { + zfcp_fsf_setup_ct_els_unchained(sbale, sg_req, sg_resp); return 0; } -- 1.8.2.3