Re: [PATCH v3 08/18] scsi: sd: set read/write commands CDL index

Hannes Reinecke
2023-01-30T18:14:06Z

On 1/28/23 01:03, Damien Le Moal wrote:
> On 1/28/23 00:30, Hannes Reinecke wrote:
>> On 1/24/23 20:02, Niklas Cassel wrote:
>>> From: Damien Le Moal <damien.lemoal@opensource.wdc.com>
>>>
>>> Introduce the command duration limits helper function
>>> sd_cdl_cmd_limit() to retrieve and set the DLD bits of the
>>> READ/WRITE 16 and READ/WRITE 32 commands to indicate to the device
>>> the command duration limit descriptor to apply to the command.
>>>
>>> When command duration limits are enabled, sd_cdl_cmd_limit() obtains the
>>> index of the descriptor to apply to the command for requests that have
>>> the IOPRIO_CLASS_DL priority class with a priority data sepcifying a
>>> valid descriptor index (1 to 7).
>>>
>>> The read-write sysfs attribute "enable" is introduced to control
>>> setting the command duration limits indexes. If this attribute is set
>>> to 0 (default), command duration limits specified by the user are
>>> ignored. The user must set this attribute to 1 for command duration
>>> limits to be set. Enabling and disabling the command duration limits
>>> feature for ATA devices must be done using the ATA feature sub-page of
>>> the control mode page. The sd_cdl_enable() function is introduced to
>>> check if this mode page is supported by the device and if it is, use
>>> it to enable/disable CDL.
>>>
>>> Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
>>> Co-developed-by: Niklas Cassel <niklas.cassel@wdc.com>
>>> Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
>>> ---
>>> drivers/scsi/sd.c | 16 +++--
>>> drivers/scsi/sd.h | 10 ++++
>>> drivers/scsi/sd_cdl.c | 134 +++++++++++++++++++++++++++++++++++++++++-
>>> 3 files changed, 152 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
>>> index 7879a5470773..d2eb01337943 100644
>>> --- a/drivers/scsi/sd.c
>>> +++ b/drivers/scsi/sd.c
>>> @@ -1045,13 +1045,14 @@ static blk_status_t sd_setup_flush_cmnd(struct scsi_cmnd *cmd)
>>>
>>> static blk_status_t sd_setup_rw32_cmnd(struct scsi_cmnd *cmd, bool write,
>>> sector_t lba, unsigned int nr_blocks,
>>> - unsigned char flags)
>>> + unsigned char flags, unsigned int dld)
>>> {
>>> cmd->cmd_len = SD_EXT_CDB_SIZE;
>>> cmd->cmnd[0] = VARIABLE_LENGTH_CMD;
>>> cmd->cmnd[7] = 0x18; /* Additional CDB len */
>>> cmd->cmnd[9] = write ? WRITE_32 : READ_32;
>>> cmd->cmnd[10] = flags;
>>> + cmd->cmnd[11] = dld & 0x07;
>>> put_unaligned_be64(lba, &cmd->cmnd[12]);
>>> put_unaligned_be32(lba, &cmd->cmnd[20]); /* Expected Indirect LBA */
>>> put_unaligned_be32(nr_blocks, &cmd->cmnd[28]);
>>> @@ -1061,12 +1062,12 @@ static blk_status_t sd_setup_rw32_cmnd(struct scsi_cmnd *cmd, bool write,
>>>
>>> static blk_status_t sd_setup_rw16_cmnd(struct scsi_cmnd *cmd, bool write,
>>> sector_t lba, unsigned int nr_blocks,
>>> - unsigned char flags)
>>> + unsigned char flags, unsigned int dld)
>>> {
>>> cmd->cmd_len = 16;
>>> cmd->cmnd[0] = write ? WRITE_16 : READ_16;
>>> - cmd->cmnd[1] = flags;
>>> - cmd->cmnd[14] = 0;
>>> + cmd->cmnd[1] = flags | ((dld >> 2) & 0x01);
>>> + cmd->cmnd[14] = (dld & 0x03) << 6;
>>> cmd->cmnd[15] = 0;
>>> put_unaligned_be64(lba, &cmd->cmnd[2]);
>>> put_unaligned_be32(nr_blocks, &cmd->cmnd[10]);
>>> @@ -1129,6 +1130,7 @@ static blk_status_t sd_setup_read_write_cmnd(struct scsi_cmnd *cmd)
>>> unsigned int mask = logical_to_sectors(sdp, 1) - 1;
>>> bool write = rq_data_dir(rq) == WRITE;
>>> unsigned char protect, fua;
>>> + unsigned int dld = 0;
>>> blk_status_t ret;
>>> unsigned int dif;
>>> bool dix;
>>> @@ -1178,6 +1180,8 @@ static blk_status_t sd_setup_read_write_cmnd(struct scsi_cmnd *cmd)
>>> fua = rq->cmd_flags & REQ_FUA ? 0x8 : 0;
>>> dix = scsi_prot_sg_count(cmd);
>>> dif = scsi_host_dif_capable(cmd->device->host, sdkp->protection_type);
>>> + if (sd_cdl_enabled(sdkp))
>>> + dld = sd_cdl_dld(sdkp, cmd);
>>>
>>> if (dif || dix)
>>> protect = sd_setup_protect_cmnd(cmd, dix, dif);
>>> @@ -1186,10 +1190,10 @@ static blk_status_t sd_setup_read_write_cmnd(struct scsi_cmnd *cmd)
>>>
>>> if (protect && sdkp->protection_type == T10_PI_TYPE2_PROTECTION) {
>>> ret = sd_setup_rw32_cmnd(cmd, write, lba, nr_blocks,
>>> - protect | fua);
>>> + protect | fua, dld);
>>> } else if (sdp->use_16_for_rw || (nr_blocks > 0xffff)) {
>>> ret = sd_setup_rw16_cmnd(cmd, write, lba, nr_blocks,
>>> - protect | fua);
>>> + protect | fua, dld);
>>> } else if ((nr_blocks > 0xff) || (lba > 0x1fffff) ||
>>> sdp->use_10_for_rw || protect) {
>>> ret = sd_setup_rw10_cmnd(cmd, write, lba, nr_blocks,
>>> diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
>>> index e60d33bd222a..5b6b6dc4b92d 100644
>>> --- a/drivers/scsi/sd.h
>>> +++ b/drivers/scsi/sd.h
>>> @@ -130,8 +130,11 @@ struct sd_cdl_page {
>>> struct sd_cdl_desc descs[SD_CDL_MAX_DESC];
>>> };
>>>
>>> +struct scsi_disk;
>>> +
>>> struct sd_cdl {
>>> struct kobject kobj;
>>> + struct scsi_disk *sdkp;
>>> bool sysfs_registered;
>>> u8 perf_vs_duration_guideline;
>>> struct sd_cdl_page pages[SD_CDL_RW];
>>> @@ -188,6 +191,7 @@ struct scsi_disk {
>>> u8 zeroing_mode;
>>> u8 nr_actuators; /* Number of actuators */
>>> struct sd_cdl *cdl;
>>> + unsigned cdl_enabled : 1;
>>> unsigned ATO : 1; /* state of disk ATO bit */
>>> unsigned cache_override : 1; /* temp override of WCE,RCD */
>>> unsigned WCE : 1; /* state of disk WCE bit */
>>> @@ -355,5 +359,11 @@ void sd_print_result(const struct scsi_disk *sdkp, const char *msg, int result);
>>> /* Command duration limits support (in sd_cdl.c) */
>>> void sd_read_cdl(struct scsi_disk *sdkp, unsigned char *buf);
>>> void sd_cdl_release(struct scsi_disk *sdkp);
>>> +int sd_cdl_dld(struct scsi_disk *sdkp, struct scsi_cmnd *scmd);
>>> +
>>> +static inline bool sd_cdl_enabled(struct scsi_disk *sdkp)
>>> +{
>>> + return sdkp->cdl && sdkp->cdl_enabled;
>>> +}
>>>
>>> #endif /* _SCSI_DISK_H */
>>> diff --git a/drivers/scsi/sd_cdl.c b/drivers/scsi/sd_cdl.c
>>> index 513cd989f19a..59d02dbb5ea1 100644
>>> --- a/drivers/scsi/sd_cdl.c
>>> +++ b/drivers/scsi/sd_cdl.c
>>> @@ -93,6 +93,63 @@ static const char *sd_cdl_policy_name(u8 policy)
>>> }
>>> }
>>>
>>> +/*
>>> + * Enable/disable CDL.
>>> + */
>>> +static int sd_cdl_enable(struct scsi_disk *sdkp, bool enable)
>>> +{
>>> + struct scsi_device *sdp = sdkp->device;
>>> + struct scsi_mode_data data;
>>> + struct scsi_sense_hdr sshdr;
>>> + struct scsi_vpd *vpd;
>>> + bool is_ata = false;
>>> + char buf[64];
>>> + int ret;
>>> +
>>> + rcu_read_lock();
>>> + vpd = rcu_dereference(sdp->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(sdp, 0x08, 0x0a, 0xf2, buf, sizeof(buf),
>>> + SD_TIMEOUT, sdkp->max_retries, &data,
>>> + NULL);
>>> + if (ret)
>>> + return -EINVAL;
>>> +
>> That is a tad odd.
>> Is CDL always enabled for 'normal' SCSI?
>
> Yes it is on the device side. There is no mode sense to turn it on/off. Not sure
> why it was designed like that in the specs... The sysfs duration_limits/enable
> attribute is a "soft" on/off switch and it is off by default, even for drives
> reporting supporting CDL.
> Hence the "if (is_ata)" to do the mode sense to enable the feature on the device
> side only for ATA devices. We need this to avoid having 2 different enable
> pathes with 2 different sysfs "enable" attributes. Doing it like this is a lot
> less code.
>
Thought as much.
No-one cares about 'real' SCSI devices anymore ;-)

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman