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>
diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index c2aea09..b090211 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -621,7 +621,16 @@
struct fd_prot fd_prot;
sense_reason_t rc;
int ret = 0;
-
+ /*
+ * We are currently limited by the number of iovecs (2048) per
+ * single vfs_[writev,readv] call.
+ */
+ if (cmd->data_length > FD_MAX_BYTES) {
+ pr_err("FILEIO: Not able to process I/O of %u bytes due to"
+ "FD_MAX_BYTES: %u iovec count limitiation\n",
+ cmd->data_length, FD_MAX_BYTES);
+ return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+ }
/*
* Call vectorized fileio functions to map struct scatterlist
* physical memory addresses to struct iovec virtual memory.