target/qla2xxx: Honor max_data_sg_nents I/O transfer limit
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@vanguard-rugged.com>
Cc: Craig Watson <craig.watson@vanguard-rugged.com>
Tested-by: Himanshu Madhani <himanshu.madhani@qlogic.com>
Cc: Roland Dreier <roland@purestorage.com>
Cc: Arun Easi <arun.easi@qlogic.com>
Cc: Giridhar Malavali <giridhar.malavali@qlogic.com>
Cc: Andrew Vasquez <andrew.vasquez@qlogic.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 3f0b500..62bafaa 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1075,6 +1075,55 @@
}
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)
{
@@ -1120,7 +1169,7 @@
}
}
- return 0;
+ return target_check_max_data_sg_nents(cmd, dev, size);
}
