Merge patch series "Add Command Duration Limits support"

Niklas Cassel <nks@flawful.org> says:

This series adds support for Command Duration Limits.
The series is based on linux tag: v6.4-rc1
The series can also be found in git: https://github.com/floatious/linux/commits/cdl-v7

=================
CDL in ATA / SCSI
=================
Command Duration Limits is defined in:
T13 ATA Command Set - 5 (ACS-5) and
T10 SCSI Primary Commands - 6 (SPC-6) respectively
(a simpler version of CDL is defined in T10 SPC-5).

CDL defines Duration Limits Descriptors (DLD).
7 DLDs for read commands and 7 DLDs for write commands.
Simply put, a DLD contains a limit and a policy.

A command can specify that a certain limit should be applied by setting
the DLD index field (3 bits, so 0-7) in the command itself.

The DLD index points to one of the 7 DLDs.
DLD index 0 means no descriptor, so no limit.
DLD index 1-7 means DLD 1-7.

A DLD can have a few different policies, but the two major ones are:
-Policy 0xF (abort), command will be completed with command aborted error
(ATA) or status CHECK CONDITION (SCSI), with sense data indicating that
the command timed out.
-Policy 0xD (complete-unavailable), command will be completed without
error (ATA) or status GOOD (SCSI), with sense data indicating that the
command timed out. Note that the command will not have transferred any
data to/from the device when the command timed out, even though the
command returned success.

Regardless of the CDL policy, in case of a CDL timeout, the I/O will
result in a -ETIME error to user-space.

The DLDs are defined in the CDL log page(s) and are readable and writable.
Reading and writing the CDL DLDs are outside the scope of the kernel.
If a user wants to read or write the descriptors, they can do so using a
user-space application that sends passthrough commands, such as cdl-tools:
https://github.com/westerndigitalcorporation/cdl-tools

================================
The introduction of ioprio hints
================================
What the kernel does provide, is a method to let I/O use one of the CDL DLDs
defined in the device. Note that the kernel will simply forward the DLD index
to the device, so the kernel currently does not know, nor does it need to know,
how the DLDs are defined inside the device.

The way that the CDL DLD index is supplied to the kernel is by introducing a
new 10 bit "ioprio hint" field within the existing 16 bit ioprio definition.

Currently, only 6 out of the 16 ioprio bits are in use, the remaining 10 bits
are unused, and are currently explicitly disallowed to be set by the kernel.

For now, we only add ioprio hints representing CDL DLD index 1-7. Additional
ioprio hints for other QoS features could be defined in the future.

A theoretical future work could be to make an I/O scheduler aware of these
hints. E.g. for CDL, an I/O scheduler could make use of the duration limit
in each descriptor, and take that information into account while scheduling
commands. Right now, the ioprio hints will be ignored by the I/O schedulers.

==============================
How to use CDL from user-space
==============================
Since CDL is mutually exclusive with NCQ priority
(see ncq_prio_enable and sas_ncq_prio_enable in
Documentation/ABI/testing/sysfs-block-device),
CDL has to be explicitly enabled using:
echo 1 > /sys/block/$bdev/device/cdl_enable

Since the ioprio hints are supplied through the existing I/O priority API,
it should be simple for an application to make use of the ioprio hints.

It simply has to reuse one of the new macros defined in
include/uapi/linux/ioprio.h: IOPRIO_PRIO_HINT() or IOPRIO_PRIO_VALUE_HINT(),
and supply one of the new hints defined in include/uapi/linux/ioprio.h:
IOPRIO_HINT_DEV_DURATION_LIMIT_[1-7], which indicates that the I/O should
use the corresponding CDL DLD index 1-7.

By reusing the I/O priority API, the user can both define a DLD to use per
AIO (io_uring sqe->ioprio or libaio iocb->aio_reqprio) or per-thread
(ioprio_set()).

=======
Testing
=======
With the following fio patches:
https://github.com/floatious/fio/commits/cdl

fio adds support for ioprio hints, such that CDL can be tested using e.g.:
fio --ioengine=io_uring --cmdprio_percentage=10 --cmdprio_hint=DLD_index

A simple way to test is to use a DLD with a very short duration limit,
and send large reads. Regardless of the CDL policy, in case of a CDL
timeout, the I/O will result in a -ETIME error to user-space.

We also provide a CDL test suite located in the cdl-tools repo, see:
https://github.com/westerndigitalcorporation/cdl-tools#testing-a-system-command-duration-limits-support

We have tested this patch series using:
-real hardware
-the following QEMU implementation:
https://github.com/floatious/qemu/tree/cdl
(NOTE: the QEMU implementation requires you to define the CDL policy at compile
time, so you currently need to recompile QEMU when switching between policies.)

===================
Further information
===================
For further information about CDL, see Damien's slides:

Presented at SDC 2021:
https://www.snia.org/sites/default/files/SDC/2021/pdfs/SNIA-SDC21-LeMoal-Be-On-Time-command-duration-limits-Feature-Support-in%20Linux.pdf

Presented at Lund Linux Con 2022:
https://drive.google.com/file/d/1I6ChFc0h4JY9qZdO1bY5oCAdYCSZVqWw/view?usp=sharing

================
Changes since V6
================
-Rebased series on v6.4-rc1.
-Picked up Reviewed-by tags from Hannes (Thank you Hannes!)
-Picked up Reviewed-by tag from Christoph (Thank you Christoph!)
-Changed KernelVersion from 6.4 to 6.5 for new sysfs attributes.

For older change logs, see previous patch series versions:
https://lore.kernel.org/linux-scsi/20230406113252.41211-1-nks@flawful.org/
https://lore.kernel.org/linux-scsi/20230404182428.715140-1-nks@flawful.org/
https://lore.kernel.org/linux-scsi/20230309215516.3800571-1-niklas.cassel@wdc.com/
https://lore.kernel.org/linux-scsi/20230124190308.127318-1-niklas.cassel@wdc.com/
https://lore.kernel.org/linux-scsi/20230112140412.667308-1-niklas.cassel@wdc.com/
https://lore.kernel.org/linux-scsi/20221208105947.2399894-1-niklas.cassel@wdc.com/

Link: https://lore.kernel.org/r/20230511011356.227789-1-nks@flawful.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

2 files changed, 17 insertions, 6 deletions

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index c2cb5f69635c..526def14e7fb 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -52,6 +52,11 @@ struct scsi_pointer {
 #define SCMD_TAGGED		(1 << 0)
 #define SCMD_INITIALIZED	(1 << 1)
 #define SCMD_LAST		(1 << 2)
+/*
+ * libata uses SCSI EH to fetch sense data for successful commands.
+ * SCSI EH should not overwrite scmd->result when SCMD_FORCE_EH_SUCCESS is set.
+ */
+#define SCMD_FORCE_EH_SUCCESS	(1 << 3)
 #define SCMD_FAIL_IF_RECOVERING	(1 << 4)
 /* flags preserved across unprep / reprep */
 #define SCMD_PRESERVED_FLAGS	(SCMD_INITIALIZED | SCMD_FAIL_IF_RECOVERING)
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index f10a008e5bfa..b2cdb078b7bd 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -218,6 +218,9 @@ struct scsi_device {
 	unsigned silence_suspend:1;	/* Do not print runtime PM related messages */
 	unsigned no_vpd_size:1;		/* No VPD size reported in header */
 
+	unsigned cdl_supported:1;	/* Command duration limits supported */
+	unsigned cdl_enable:1;		/* Enable/disable Command duration limits */
+
 	unsigned int queue_stopped;	/* request queue is quiesced */
 	bool offline_already;		/* Device offline message logged */
 
@@ -364,6 +367,8 @@ extern int scsi_register_device_handler(struct scsi_device_handler *scsi_dh);
 extern void scsi_remove_device(struct scsi_device *);
 extern int scsi_unregister_device_handler(struct scsi_device_handler *scsi_dh);
 void scsi_attach_vpd(struct scsi_device *sdev);
+void scsi_cdl_check(struct scsi_device *sdev);
+int scsi_cdl_enable(struct scsi_device *sdev, bool enable);
 
 extern struct scsi_device *scsi_device_from_queue(struct request_queue *q);
 extern int __must_check scsi_device_get(struct scsi_device *);
@@ -421,10 +426,10 @@ extern int scsi_track_queue_full(struct scsi_device *, int);
 
 extern int scsi_set_medium_removal(struct scsi_device *, char);
 
-extern int scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
-			   unsigned char *buffer, int len, int timeout,
-			   int retries, struct scsi_mode_data *data,
-			   struct scsi_sense_hdr *);
+int scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
+		    int subpage, unsigned char *buffer, int len, int timeout,
+		    int retries, struct scsi_mode_data *data,
+		    struct scsi_sense_hdr *);
 extern int scsi_mode_select(struct scsi_device *sdev, int pf, int sp,
 			    unsigned char *buffer, int len, int timeout,
 			    int retries, struct scsi_mode_data *data,
@@ -433,8 +438,9 @@ extern int scsi_test_unit_ready(struct scsi_device *sdev, int timeout,
 				int retries, struct scsi_sense_hdr *sshdr);
 extern int scsi_get_vpd_page(struct scsi_device *, u8 page, unsigned char *buf,
 			     int buf_len);
-extern int scsi_report_opcode(struct scsi_device *sdev, unsigned char *buffer,
-			      unsigned int len, unsigned char opcode);
+int scsi_report_opcode(struct scsi_device *sdev, unsigned char *buffer,
+		       unsigned int len, unsigned char opcode,
+		       unsigned short sa);
 extern int scsi_device_set_state(struct scsi_device *sdev,
 				 enum scsi_device_state state);
 extern struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,