On Tue, Apr 04, 2023 at 08:24:14PM +0200, Niklas Cassel wrote:
> From: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
>
> Add the sysfs scsi device attribute cdl_enable to allow a user to turn
> enable or disable a device command duration limits feature. CDL is
> disabled by default. This feature must be explicitly enabled by a user by
> setting the cdl_enable attribute to 1.
>
> The new function scsi_cdl_enable() does not do anything beside setting
> the cdl_enable field of struct scsi_device in the case of a (real) scsi
> device (e.g. a SAS HDD). For ATA devices, the command duration limits
> feature needs to be enabled/disabled using the ATA feature sub-page of
> the control mode page. To do so, the scsi_cdl_enable() function checks
> if this mode page is supported using scsi_mode_sense(). If it is,
> scsi_mode_select() is used to enable and disable CDL.
>
> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
> Co-developed-by: Niklas Cassel <niklas.cassel@xxxxxxx>
> Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
> ---
> Documentation/ABI/testing/sysfs-block-device | 13 ++++
> drivers/scsi/scsi.c | 62 ++++++++++++++++++++
> drivers/scsi/scsi_sysfs.c | 31 ++++++++++
> include/scsi/scsi_device.h | 2 +
> 4 files changed, 108 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-block-device b/Documentation/ABI/testing/sysfs-block-device
> index ee3610a25845..626d48ac504b 100644
> --- a/Documentation/ABI/testing/sysfs-block-device
> +++ b/Documentation/ABI/testing/sysfs-block-device
> @@ -104,3 +104,16 @@ Contact: linux-scsi@xxxxxxxxxxxxxxx
> Description:
> (RO) Indicates if the device supports the command duration
> limits feature found in some ATA and SCSI devices.
> +
> +
> +What: /sys/block/*/device/cdl_enable
> +Date: Mar, 2023
> +KernelVersion: v6.4
> +Contact: linux-scsi@xxxxxxxxxxxxxxx
> +Description:
> + (RW) For a device supporting the command duration limits
> + feature, write to the file to turn on or off the feature.
> + By default this feature is turned off.
> + Writing "1" to this file enables the use of command duration
> + limits for read and write commands in the kernel and turns on
> + the feature on the device. Writing "0" disables the feature.
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index c03814ce23ca..c4bf99a842f3 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -651,6 +651,68 @@ void scsi_cdl_check(struct scsi_device *sdev)
> kfree(buf);
> }
>
> +/**
> + * scsi_cdl_enable - Enable or disable a SCSI device supports for Command
> + * Duration Limits
> + * @sdev: The target device
> + * @enable: the target state
> + */
> +int scsi_cdl_enable(struct scsi_device *sdev, bool enable)
> +{
> + struct scsi_mode_data data;
> + struct scsi_sense_hdr sshdr;
> + struct scsi_vpd *vpd;
> + bool is_ata = false;
> + char buf[64];
> + int ret;
> +
> + if (!sdev->cdl_supported)
> + return -EOPNOTSUPP;
> +
> + rcu_read_lock();
> + vpd = rcu_dereference(sdev->vpd_pg89);
> + if (vpd)
> + is_ata = true;
> + rcu_read_unlock();
> +
> + /*
> + * For ATA devices, CDL needs to be enabled with a SET FEATURES command.
> + */
> + if (is_ata) {
> + char *buf_data;
> + int len;
> +
> + ret = scsi_mode_sense(sdev, 0x08, 0x0a, 0xf2, buf, sizeof(buf),
> + 5 * HZ, 3, &data, NULL);
> + if (ret)
> + return -EINVAL;
> +
> + /* Enable CDL using the ATA feature page */
> + len = min_t(size_t, sizeof(buf),
> + data.length - data.header_length -
> + data.block_descriptor_length);
> + buf_data = buf + data.header_length +
> + data.block_descriptor_length;
> + if (enable)
> + buf_data[4] = 0x02;
> + else
> + buf_data[4] = 0;
> +
> + ret = scsi_mode_select(sdev, 1, 0, buf_data, len, 5 * HZ, 3,
> + &data, &sshdr);
> + if (ret) {
> + if (scsi_sense_valid(&sshdr))
> + scsi_print_sense_hdr(sdev,
> + dev_name(&sdev->sdev_gendev), &sshdr);
> + return ret;
> + }
> + }
> +
> + sdev->cdl_enable = enable;
> +
> + return 0;
> +}
> +
> /**
> * scsi_device_get - get an additional reference to a scsi_device
> * @sdev: device to get a reference to
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 4994148e685b..9a54b2c0fee7 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1222,6 +1222,36 @@ static DEVICE_ATTR(queue_ramp_up_period, S_IRUGO | S_IWUSR,
> sdev_show_queue_ramp_up_period,
> sdev_store_queue_ramp_up_period);
>
> +static ssize_t sdev_show_cdl_enable(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct scsi_device *sdev = to_scsi_device(dev);
> +
> + return sysfs_emit(buf, "%d\n", (int)sdev->cdl_enable);
> +}
> +
> +static ssize_t sdev_store_cdl_enable(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + int ret;
> + bool v;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EACCES;
CAP_SYS_ADMIN seems be too restrictive. NCQ PRIO (ncq_prio_enable) does not
require CAP_SYS_ADMIN. Since NCQ PRIO and CDL are mutually exclusive a user
should be able to toggle both features.
Thanks,
Igor
> +
> + if (kstrtobool(buf, &v))
> + return -EINVAL;
> +
> + ret = scsi_cdl_enable(to_scsi_device(dev), v);
> + if (ret)
> + return ret;
> +
> + return count;
> +}
> +static DEVICE_ATTR(cdl_enable, S_IRUGO | S_IWUSR,
> + sdev_show_cdl_enable, sdev_store_cdl_enable);
> +
> static umode_t scsi_sdev_attr_is_visible(struct kobject *kobj,
> struct attribute *attr, int i)
> {
> @@ -1302,6 +1332,7 @@ static struct attribute *scsi_sdev_attrs[] = {
> #endif
> &dev_attr_queue_ramp_up_period.attr,
> &dev_attr_cdl_supported.attr,
> + &dev_attr_cdl_enable.attr,
> REF_EVT(media_change),
> REF_EVT(inquiry_change_reported),
> REF_EVT(capacity_change_reported),
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index 6b8df9e253a0..b2cdb078b7bd 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -219,6 +219,7 @@ struct scsi_device {
> 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 */
> @@ -367,6 +368,7 @@ 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 *);
> --
> 2.39.2
>
