From: Nicholas Bellinger <nab@linux-iscsi.org>
Date: Fri, 31 Jul 2015 01:28:13 +0000 (-0700)
Subject: target/qla2xxx: Honor max_data_sg_nents I/O transfer limit
X-Git-Tag: omap-for-v4.3/fixes-rc1~24^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8f9b565482c537821588444e09ff732c7d65ed6e;p=pandora-kernel.git

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/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
index c621623abeed..edeb3aefa6fe 100644
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
@@ -1808,6 +1808,11 @@ 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 a07d455e0dd5..0e0456f6a282 100644
--- a/drivers/target/target_core_spc.c
+++ b/drivers/target/target_core_spc.c
@@ -477,8 +477,8 @@ 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
@@ -509,8 +509,15 @@ 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
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