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Gleb Chesnokov
e7ad7e093e
The scst_user specification copies ioctl structures and command payloads that predate several ABI extensions. Building a handler from those layouts can select the wrong union member, alignment or completion path. Commit3fc775c75a("EXTENDED COPY support") added remapping payloads. Commitdaee4dcb7e("WRITE SAME command improvements") added WRITE SAME descriptors. Commitd1bd22afd9("scst_user: avoid global locks") left the explicit unregister ioctl as an obsolete no-op. Use scst/include/scst_user.h and scst_user.c as the producer-side source of truth. Synchronize registration, command, reply and subcommand layouts, version checks, reserved fields and ioctl rules. Update the fileio_tgt, stpgd and event guides from current code. Make live-storage and event-consumption risks explicit.
stpgd explicit ALUA helper ========================== stpgd is the user-space consumer for explicit ALUA state-transition events. It opens the SCST event device, subscribes to events issued by the SCST core, and handles SCST_EVENT_STPG_USER_INVOKE by executing an external helper once for each target-port-group descriptor. The helper's exit status is reported back to the kernel through SCST_EVENT_NOTIFY_DONE. The event payload and ioctl ABI are defined in scst/include/scst_event.h. The current event filtering, helper invocation, timeout handling, and command-line parsing are implemented in usr/stpgd/stpgd_main.c. Build and invocation -------------------- From the repository root, "make usr" builds stpgd and fileio_tgt. To build only this daemon, run "make -C usr/stpgd". Installation is a separate, privileged operation. stpgd [OPTIONS] - -f, --foreground: do not daemonize - -p, --path=PATH: absolute path to the executable transition helper - -t, --timeout=SECONDS: helper timeout; the default is 17 seconds - -v, --version: print the program version - -h, --help: print usage information The -d/--debug option is present only when tracing or debugging is compiled in. Without -p, the daemon uses /usr/local/bin/scst/scst_on_stpg. If a different installation prefix is used, pass the installed helper path explicitly. Helper interface ---------------- The helper receives these five positional arguments, in order: 1. SCST device name 2. previous ALUA state 3. requested ALUA state 4. device-group name 5. target-group name The same values are supplied as SCST_DEVICE_NAME, SCST_PREV_ALUA_STATE, SCST_ALUA_STATE, SCST_DEVICE_GROUP, and SCST_TARGET_GROUP in the helper's environment. The daemon supplies a restricted PATH containing /bin, /usr/bin, /sbin, and /usr/sbin. Safety ------ usr/stpgd/scst_on_stpg is only a minimal example. It writes the requested state directly to the target group's live SCST sysfs attribute; it does not coordinate replication, fencing, failover, or cluster-manager state. Do not run stpgd or deploy that helper until the transition workflow has been adapted and validated for the exact hosts, storage, target groups, and HA stack. SCST blocks the affected devices around the explicit transition event, as described in the explicit ALUA section of scst/README. The external helper is still responsible for performing every site-specific transition safely.