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authorChristof Schmitt <christof.schmitt@de.ibm.com>2009-07-13 15:06:06 +0200
committerJames Bottomley <James.Bottomley@HansenPartnership.com>2009-07-30 08:49:56 -0500
commit426f6059b0eb66cec139f4b9066168ab72b85774 (patch)
tree5a117d5f0a885b591bea2b6bdf8475fb6745f2af /drivers/s390/scsi
parent688a1820bde27749f22b18b94ef1c9bc179b1b29 (diff)
[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 <swen@vnet.ibm.com> Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Diffstat (limited to 'drivers/s390/scsi')
-rw-r--r--drivers/s390/scsi/zfcp_fsf.c33
1 files changed, 25 insertions, 8 deletions
diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index c4eb62b32a3..bec912547fb 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;
}