On 10/30/2018 09:26 AM, David Disseldorp wrote:
> The new emulate_pr backstore attribute allows for Persistent Reservation
> and SCSI2 RESERVE/RELEASE support to be completely disabled. This can be
> useful for scenarios such as:
> - Ensuring ATS (Compare & Write) usage on recent VMware ESXi initiators.
> - Allowing clustered (e.g. tcm-user) backends to block such requests,
> avoiding the need for multi-node reservation state propagation.
>
> When explicitly disabled, PR and RESERVE/RELEASE requests receive
> Invalid Command Operation Code response sense data.
>
> Signed-off-by: David Disseldorp <ddiss@xxxxxxx>
> ---
> drivers/target/target_core_configfs.c | 32 ++++++++++++++++++++++++--------
> drivers/target/target_core_device.c | 13 +++++++++++++
> drivers/target/target_core_pr.c | 2 ++
> drivers/target/target_core_spc.c | 8 ++++++++
> include/target/target_core_base.h | 3 +++
> 5 files changed, 50 insertions(+), 8 deletions(-)
>
> Changes since v3:
> * rebase against current mainline
>
> Changes since v2:
> * handle target_pr_res_aptpl_metadata_store()
> * use common error path for spc_parse_cdb() and passthrough_parse_cdb()
> checks
> * drop erroneous TRANSPORT_FLAG_PASSTHROUGH_PGR ->
> TRANSPORT_FLAG_PASSTHROUGH changes
>
> Changes since v1:
> * block Reservation request passthrough when emulate_pr=0
> * fix some style issues
> * add an emulate_pr check to pgr_support_show()
>
> diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
> index f6b1549f4142..bacb771a333e 100644
> --- a/drivers/target/target_core_configfs.c
> +++ b/drivers/target/target_core_configfs.c
> @@ -532,6 +532,7 @@ DEF_CONFIGFS_ATTRIB_SHOW(emulate_tpu);
> DEF_CONFIGFS_ATTRIB_SHOW(emulate_tpws);
> DEF_CONFIGFS_ATTRIB_SHOW(emulate_caw);
> DEF_CONFIGFS_ATTRIB_SHOW(emulate_3pc);
> +DEF_CONFIGFS_ATTRIB_SHOW(emulate_pr);
> DEF_CONFIGFS_ATTRIB_SHOW(pi_prot_type);
> DEF_CONFIGFS_ATTRIB_SHOW(hw_pi_prot_type);
> DEF_CONFIGFS_ATTRIB_SHOW(pi_prot_format);
> @@ -592,6 +593,7 @@ static ssize_t _name##_store(struct config_item *item, const char *page, \
> DEF_CONFIGFS_ATTRIB_STORE_BOOL(emulate_fua_write);
> DEF_CONFIGFS_ATTRIB_STORE_BOOL(emulate_caw);
> DEF_CONFIGFS_ATTRIB_STORE_BOOL(emulate_3pc);
> +DEF_CONFIGFS_ATTRIB_STORE_BOOL(emulate_pr);
> DEF_CONFIGFS_ATTRIB_STORE_BOOL(enforce_pr_isids);
> DEF_CONFIGFS_ATTRIB_STORE_BOOL(is_nonrot);
>
> @@ -1100,9 +1102,13 @@ static ssize_t pgr_support_show(struct config_item *item, char *page)
> {
> struct se_dev_attrib *da = to_attrib(item);
> u8 flags = da->da_dev->transport->transport_flags;
> + int pgr_support = 1;
>
> - return snprintf(page, PAGE_SIZE, "%d\n",
> - flags & TRANSPORT_FLAG_PASSTHROUGH_PGR ? 0 : 1);
> + if (!da->da_dev->dev_attrib.emulate_pr ||
> + (flags & TRANSPORT_FLAG_PASSTHROUGH_PGR))
> + pgr_support = 0;
> +
I think we want to keep this separate still. The file tells userspace if
PRs are supported in the backend module/device or in LIO core.
With the chunk above, if you had emulate_pr=0 and
TRANSPORT_FLAG_PASSTHROUGH_PGR is set, userspace cannot detect what the
backend supports. We would have to temporarily set emaulate_pr sow e can
read the file then clear it.
