From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Hi Arun, Roland & Co,
Based upon the feedback from last week, here is a proper
patch for target-core to honor a fabric provided SGL limit
using residual count plus underflow response bit.
Everything appears to be working as expected with tcm-loop
LUNs with basic I/O and sg_raw to test CDB underflow, but
still needs to be verified on real qla2xxx hardware over
the next days for v4.2.0 code.
Please review + test.
--nab
This patch adds an optional fabric driver provided SGL limit
that target-core will honor as it's own internal I/O maximum
transfer length limit, as exposed by EVPD=0xb0 block limits
parameters.
This is required for handling cases when host I/O transfer
length exceeds the requested EVPD block limits maximum
transfer length. The initial user of this logic is qla2xxx,
so that we can avoid having to reject I/Os from some legacy
FC hosts where EVPD=0xb0 parameters are not honored.
When se_cmd payload length exceeds the provided limit in
target_check_max_data_sg_nents() code, se_cmd->data_length +
se_cmd->prot_length are reset with se_cmd->residual_count
plus underflow bit for outgoing TFO response callbacks.
It also checks for existing CDB level underflow + overflow
and recalculates final residual_count as necessary.
Note this patch currently assumes 1:1 mapping of PAGE_SIZE
per struct scatterlist entry.
Reported-by: Craig Watson <craig.watson@xxxxxxxxxxxxxxxxxxx>
Cc: Craig Watson <craig.watson@xxxxxxxxxxxxxxxxxxx>
Cc: Roland Dreier <roland@xxxxxxxxxxxxxxx>
Cc: Arun Easi <arun.easi@xxxxxxxxxx>
Cc: Giridhar Malavali <giridhar.malavali@xxxxxxxxxx>
Cc: Andrew Vasquez <andrew.vasquez@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/scsi/qla2xxx/tcm_qla2xxx.c | 5 ++++
drivers/target/target_core_spc.c | 13 +++++++--
drivers/target/target_core_transport.c | 51 +++++++++++++++++++++++++++++++++-
include/target/target_core_fabric.h | 13 +++++++++
4 files changed, 78 insertions(+), 4 deletions(-)
diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
index 9224a06..6649809 100644
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
@@ -1804,6 +1804,11 @@ static const struct target_core_fabric_ops tcm_qla2xxx_ops = {
.module = THIS_MODULE,
.name = "qla2xxx",
.node_acl_size = sizeof(struct tcm_qla2xxx_nacl),
+ /*
+ * XXX: Limit assumes single page per scatter-gather-list entry.
+ * Current maximum is ~4.9 MB per se_cmd->t_data_sg with PAGE_SIZE=4096
+ */
+ .max_data_sg_nents = 1200,
.get_fabric_name = tcm_qla2xxx_get_fabric_name,
.tpg_get_wwn = tcm_qla2xxx_get_fabric_wwn,
.tpg_get_tag = tcm_qla2xxx_get_tag,
diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
index 556ea1b..da6130a 100644
--- a/drivers/target/target_core_spc.c
+++ b/drivers/target/target_core_spc.c
@@ -484,8 +484,8 @@ static sense_reason_t
spc_emulate_evpd_b0(struct se_cmd *cmd, unsigned char *buf)
{
struct se_device *dev = cmd->se_dev;
- int have_tp = 0;
- int opt, min;
+ u32 mtl = 0;
+ int have_tp = 0, opt, min;
/*
* Following spc3r22 section 6.5.3 Block Limits VPD page, when
@@ -516,8 +516,15 @@ spc_emulate_evpd_b0(struct se_cmd *cmd, unsigned char *buf)
/*
* Set MAXIMUM TRANSFER LENGTH
+ *
+ * XXX: Currently assumes single PAGE_SIZE per scatterlist for fabrics
+ * enforcing maximum HW scatter-gather-list entry limit
*/
- put_unaligned_be32(dev->dev_attrib.hw_max_sectors, &buf[8]);
+ if (cmd->se_tfo->max_data_sg_nents) {
+ mtl = (cmd->se_tfo->max_data_sg_nents * PAGE_SIZE) /
+ dev->dev_attrib.block_size;
+ }
+ put_unaligned_be32(min_not_zero(mtl, dev->dev_attrib.hw_max_sectors), &buf[8]);
/*
* Set OPTIMAL TRANSFER LENGTH
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index ce8574b..652471a1 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1074,6 +1074,55 @@ transport_set_vpd_ident(struct t10_vpd *vpd, unsigned char *page_83)
}
EXPORT_SYMBOL(transport_set_vpd_ident);
+static sense_reason_t
+target_check_max_data_sg_nents(struct se_cmd *cmd, struct se_device *dev,
+ unsigned int size)
+{
+ u32 mtl;
+
+ if (!cmd->se_tfo->max_data_sg_nents)
+ return TCM_NO_SENSE;
+ /*
+ * Check if fabric enforced maximum SGL entries per I/O descriptor
+ * exceeds se_cmd->data_length. If true, set SCF_UNDERFLOW_BIT +
+ * residual_count and reduce original cmd->data_length to maximum
+ * length based on single PAGE_SIZE entry scatter-lists.
+ */
+ mtl = (cmd->se_tfo->max_data_sg_nents * PAGE_SIZE);
+ if (cmd->data_length > mtl) {
+ /*
+ * If an existing CDB overflow is present, calculate new residual
+ * based on CDB size minus fabric maximum transfer length.
+ *
+ * If an existing CDB underflow is present, calculate new residual
+ * based on original cmd->data_length minus fabric maximum transfer
+ * length.
+ *
+ * Otherwise, set the underflow residual based on cmd->data_length
+ * minus fabric maximum transfer length.
+ */
+ if (cmd->se_cmd_flags & SCF_OVERFLOW_BIT) {
+ cmd->residual_count = (size - mtl);
+ } else if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
+ u32 orig_dl = size + cmd->residual_count;
+ cmd->residual_count = (orig_dl - mtl);
+ } else {
+ cmd->se_cmd_flags |= SCF_UNDERFLOW_BIT;
+ cmd->residual_count = (cmd->data_length - mtl);
+ }
+ cmd->data_length = mtl;
+ /*
+ * Reset sbc_check_prot() calculated protection payload
+ * length based upon the new smaller MTL.
+ */
+ if (cmd->prot_length) {
+ u32 sectors = (mtl / dev->dev_attrib.block_size);
+ cmd->prot_length = dev->prot_length * sectors;
+ }
+ }
+ return TCM_NO_SENSE;
+}
+
sense_reason_t
target_cmd_size_check(struct se_cmd *cmd, unsigned int size)
{
@@ -1119,7 +1168,7 @@ target_cmd_size_check(struct se_cmd *cmd, unsigned int size)
}
}
- return 0;
+ return target_check_max_data_sg_nents(cmd, dev, size);
}
diff --git a/include/target/target_core_fabric.h b/include/target/target_core_fabric.h
index 18afef9..995f2e1 100644
--- a/include/target/target_core_fabric.h
+++ b/include/target/target_core_fabric.h
@@ -5,6 +5,19 @@ struct target_core_fabric_ops {
struct module *module;
const char *name;
size_t node_acl_size;
+ /*
+ * Limits number of scatterlist entries per SCF_SCSI_DATA_CDB payload.
+ * Setting this value tells target-core to enforce this limit, and
+ * report as INQUIRY EVPD=b0 MAXIMUM TRANSFER LENGTH.
+ *
+ * target-core will currently reset se_cmd->data_length to this
+ * maximum size, and set OVERFLOW residual count if length exceeds
+ * this limit.
+ *
+ * XXX: Not all initiator hosts honor this block-limit EVPD
+ * XXX: Currently assumes single PAGE_SIZE per scatterlist entry
+ */
+ u32 max_data_sg_nents;
char *(*get_fabric_name)(void);
char *(*tpg_get_wwn)(struct se_portal_group *);
u16 (*tpg_get_tag)(struct se_portal_group *);
--
1.9.1
--
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