target: Untangle front-end and back-end meanings of max_sectors attribute

se_dev_attrib.max_sectors currently has two independent meanings:

 - It is reported in the block limits VPD page as the maximum transfer
   length, ie the largest IO that the front-end (fabric) can handle.
   Also the target core doesn't enforce this maximum transfer length.

 - It is used to hold the size of the largest IO that the back-end can
   handle, so we know when to split SCSI commands into multiple tasks.

Fix this by adding a new se_dev_attrib.fabric_max_sectors to hold the
maximum transfer length, and checking incoming IOs against that limit.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

5 files changed, 73 insertions, 7 deletions

diff --git a/drivers/target/target_core_cdb.c b/drivers/target/target_core_cdb.c
index 4f65b258cc25..41ca2d43377b 100644
--- a/drivers/target/target_core_cdb.c
+++ b/drivers/target/target_core_cdb.c
@@ -456,7 +456,7 @@ target_emulate_evpd_b0(struct se_cmd *cmd, unsigned char *buf)
         /*
          * Set MAXIMUM TRANSFER LENGTH
          */
-        put_unaligned_be32(dev->se_sub_dev->se_dev_attrib.max_sectors, &buf[8]);
+        put_unaligned_be32(dev->se_sub_dev->se_dev_attrib.fabric_max_sectors, &buf[8]);
 
         /*
          * Set OPTIMAL TRANSFER LENGTH
diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index 0700d3b3d1c0..ac0ee5021c29 100644
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -702,6 +702,9 @@ SE_DEV_ATTR_RO(hw_max_sectors);
 DEF_DEV_ATTRIB(max_sectors);
 SE_DEV_ATTR(max_sectors, S_IRUGO | S_IWUSR);
 
+DEF_DEV_ATTRIB(fabric_max_sectors);
+SE_DEV_ATTR(fabric_max_sectors, S_IRUGO | S_IWUSR);
+
 DEF_DEV_ATTRIB(optimal_sectors);
 SE_DEV_ATTR(optimal_sectors, S_IRUGO | S_IWUSR);
 
@@ -741,6 +744,7 @@ static struct configfs_attribute *target_core_dev_attrib_attrs[] = {
         &target_core_dev_attrib_block_size.attr,
         &target_core_dev_attrib_hw_max_sectors.attr,
         &target_core_dev_attrib_max_sectors.attr,
+        &target_core_dev_attrib_fabric_max_sectors.attr,
         &target_core_dev_attrib_optimal_sectors.attr,
         &target_core_dev_attrib_hw_queue_depth.attr,
         &target_core_dev_attrib_queue_depth.attr,
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 0b25b50900e9..27da4e4e07c6 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -889,10 +889,15 @@ void se_dev_set_default_attribs(
                                                 limits->logical_block_size);
         dev->se_sub_dev->se_dev_attrib.max_sectors = limits->max_sectors;
         /*
-         * Set optimal_sectors from max_sectors, which can be lowered via
-         * configfs.
+         * Set fabric_max_sectors, which is reported in block limits
+         * VPD page (B0h).
          */
-        dev->se_sub_dev->se_dev_attrib.optimal_sectors = limits->max_sectors;
+        dev->se_sub_dev->se_dev_attrib.fabric_max_sectors = DA_FABRIC_MAX_SECTORS;
+        /*
+         * Set optimal_sectors from fabric_max_sectors, which can be
+         * lowered via configfs.
+         */
+        dev->se_sub_dev->se_dev_attrib.optimal_sectors = DA_FABRIC_MAX_SECTORS;
         /*
          * queue_depth is based on subsystem plugin dependent requirements.
          */
@@ -1224,6 +1229,54 @@ int se_dev_set_max_sectors(struct se_device *dev, u32 max_sectors)
         return 0;
 }
 
+int se_dev_set_fabric_max_sectors(struct se_device *dev, u32 fabric_max_sectors)
+{
+        if (atomic_read(&dev->dev_export_obj.obj_access_count)) {
+                pr_err("dev[%p]: Unable to change SE Device"
+                        " fabric_max_sectors while dev_export_obj: %d count exists\n",
+                        dev, atomic_read(&dev->dev_export_obj.obj_access_count));
+                return -EINVAL;
+        }
+        if (!fabric_max_sectors) {
+                pr_err("dev[%p]: Illegal ZERO value for"
+                        " fabric_max_sectors\n", dev);
+                return -EINVAL;
+        }
+        if (fabric_max_sectors < DA_STATUS_MAX_SECTORS_MIN) {
+                pr_err("dev[%p]: Passed fabric_max_sectors: %u less than"
+                        " DA_STATUS_MAX_SECTORS_MIN: %u\n", dev, fabric_max_sectors,
+                                DA_STATUS_MAX_SECTORS_MIN);
+                return -EINVAL;
+        }
+        if (dev->transport->transport_type == TRANSPORT_PLUGIN_PHBA_PDEV) {
+                if (fabric_max_sectors > dev->se_sub_dev->se_dev_attrib.hw_max_sectors) {
+                        pr_err("dev[%p]: Passed fabric_max_sectors: %u"
+                                " greater than TCM/SE_Device max_sectors:"
+                                " %u\n", dev, fabric_max_sectors,
+                                dev->se_sub_dev->se_dev_attrib.hw_max_sectors);
+                         return -EINVAL;
+                }
+        } else {
+                if (fabric_max_sectors > DA_STATUS_MAX_SECTORS_MAX) {
+                        pr_err("dev[%p]: Passed fabric_max_sectors: %u"
+                                " greater than DA_STATUS_MAX_SECTORS_MAX:"
+                                " %u\n", dev, fabric_max_sectors,
+                                DA_STATUS_MAX_SECTORS_MAX);
+                        return -EINVAL;
+                }
+        }
+        /*
+         * Align max_sectors down to PAGE_SIZE to follow transport_allocate_data_tasks()
+         */
+        fabric_max_sectors = se_dev_align_max_sectors(fabric_max_sectors,
+                                                      dev->se_sub_dev->se_dev_attrib.block_size);
+
+        dev->se_sub_dev->se_dev_attrib.fabric_max_sectors = fabric_max_sectors;
+        pr_debug("dev[%p]: SE Device max_sectors changed to %u\n",
+                        dev, fabric_max_sectors);
+        return 0;
+}
+
 int se_dev_set_optimal_sectors(struct se_device *dev, u32 optimal_sectors)
 {
         if (atomic_read(&dev->dev_export_obj.obj_access_count)) {
@@ -1237,10 +1290,10 @@ int se_dev_set_optimal_sectors(struct se_device *dev, u32 optimal_sectors)
                                 " changed for TCM/pSCSI\n", dev);
                 return -EINVAL;
         }
-        if (optimal_sectors > dev->se_sub_dev->se_dev_attrib.max_sectors) {
+        if (optimal_sectors > dev->se_sub_dev->se_dev_attrib.fabric_max_sectors) {
                 pr_err("dev[%p]: Passed optimal_sectors %u cannot be"
-                        " greater than max_sectors: %u\n", dev,
-                        optimal_sectors, dev->se_sub_dev->se_dev_attrib.max_sectors);
+                        " greater than fabric_max_sectors: %u\n", dev,
+                        optimal_sectors, dev->se_sub_dev->se_dev_attrib.fabric_max_sectors);
                 return -EINVAL;
         }
 
diff --git a/drivers/target/target_core_internal.h b/drivers/target/target_core_internal.h
index b026dedb8184..21c05638f158 100644
--- a/drivers/target/target_core_internal.h
+++ b/drivers/target/target_core_internal.h
@@ -53,6 +53,7 @@ int	se_dev_set_is_nonrot(struct se_device *, int);
 int     se_dev_set_emulate_rest_reord(struct se_device *dev, int);
 int     se_dev_set_queue_depth(struct se_device *, u32);
 int     se_dev_set_max_sectors(struct se_device *, u32);
+int     se_dev_set_fabric_max_sectors(struct se_device *, u32);
 int     se_dev_set_optimal_sectors(struct se_device *, u32);
 int     se_dev_set_block_size(struct se_device *, u32);
 struct se_lun *core_dev_add_lun(struct se_portal_group *, struct se_hba *,
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 19804b6fdbaa..b79c6a2824ee 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -37,6 +37,7 @@
 #include <linux/in.h>
 #include <linux/cdrom.h>
 #include <linux/module.h>
+#include <linux/ratelimit.h>
 #include <asm/unaligned.h>
 #include <net/sock.h>
 #include <net/tcp.h>
@@ -3107,6 +3108,13 @@ static int transport_generic_cmd_sequencer(
                 cmd->data_length = size;
         }
 
+        if (cmd->se_cmd_flags & SCF_SCSI_DATA_SG_IO_CDB &&
+            sectors > dev->se_sub_dev->se_dev_attrib.fabric_max_sectors) {
+                printk_ratelimited(KERN_ERR "SCSI OP %02xh with too big sectors %u\n",
+                                   cdb[0], sectors);
+                goto out_invalid_cdb_field;
+        }
+
         /* reject any command that we don't have a handler for */
         if (!(passthrough || cmd->execute_task ||
              (cmd->se_cmd_flags & SCF_SCSI_DATA_SG_IO_CDB)))