target: Drop arbitrary maximum I/O size limit

This patch drops the arbitrary maximum I/O size limit in sbc_parse_cdb(),
which currently for fabric_max_sectors is hardcoded to 8192 (4 MB for 512
byte sector devices), and for hw_max_sectors is a backend driver dependent
value.

This limit is problematic because Linux initiators have only recently
started to honor block limits MAXIMUM TRANSFER LENGTH, and other non-Linux
based initiators (eg: MSFT Fibre Channel) can also generate I/Os larger
than 4 MB in size.

Currently when this happens, the following message will appear on the
target resulting in I/Os being returned with non recoverable status:

  SCSI OP 28h with too big sectors 16384 exceeds fabric_max_sectors: 8192

Instead, drop both [fabric,hw]_max_sector checks in sbc_parse_cdb(),
and convert the existing hw_max_sectors into a purely informational
attribute used to represent the granuality that backend driver and/or
subsystem code is splitting I/Os upon.

Also, update FILEIO with an explicit FD_MAX_BYTES check in fd_execute_rw()
to deal with the one special iovec limitiation case.

v2 changes:
  - Drop hw_max_sectors check in sbc_parse_cdb()

Reported-by: Lance Gropper <lance.gropper@qosserver.com>
Reported-by: Stefan Priebe <s.priebe@profihost.ag>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Roland Dreier <roland@purestorage.com>
Cc: stable@vger.kernel.org # 3.4
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 7653cfb027a2..ee4b89fb8841 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -1156,10 +1156,10 @@ int se_dev_set_optimal_sectors(struct se_device *dev, u32 optimal_sectors)
 			dev, dev->export_count);
 		return -EINVAL;
 	}
-	if (optimal_sectors > dev->dev_attrib.fabric_max_sectors) {
+	if (optimal_sectors > dev->dev_attrib.hw_max_sectors) {
 		pr_err("dev[%p]: Passed optimal_sectors %u cannot be"
-			" greater than fabric_max_sectors: %u\n", dev,
-			optimal_sectors, dev->dev_attrib.fabric_max_sectors);
+			" greater than hw_max_sectors: %u\n", dev,
+			optimal_sectors, dev->dev_attrib.hw_max_sectors);
 		return -EINVAL;
 	}
 
@@ -1554,7 +1554,6 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
 				DA_UNMAP_GRANULARITY_ALIGNMENT_DEFAULT;
 	dev->dev_attrib.max_write_same_len = DA_MAX_WRITE_SAME_LEN;
 	dev->dev_attrib.fabric_max_sectors = DA_FABRIC_MAX_SECTORS;
-	dev->dev_attrib.optimal_sectors = DA_FABRIC_MAX_SECTORS;
 
 	xcopy_lun = &dev->xcopy_lun;
 	xcopy_lun->lun_se_dev = dev;
@@ -1595,6 +1594,7 @@ int target_configure_device(struct se_device *dev)
 	dev->dev_attrib.hw_max_sectors =
 		se_dev_align_max_sectors(dev->dev_attrib.hw_max_sectors,
 					 dev->dev_attrib.hw_block_size);
+	dev->dev_attrib.optimal_sectors = dev->dev_attrib.hw_max_sectors;
 
 	dev->dev_index = scsi_get_new_index(SCSI_DEVICE_INDEX);
 	dev->creation_time = get_jiffies_64();