mirror of
https://github.com/SCST-project/scst.git
synced 2026-08-28 20:06:33 +00:00
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.
71 lines
3.0 KiB
Plaintext
71 lines
3.0 KiB
Plaintext
User space FILEIO handler
|
|
=========================
|
|
|
|
Version 3.11.0-pre, 29 December 2025
|
|
------------------------------------
|
|
|
|
fileio_tgt is a user-space disk handler that demonstrates and exercises the
|
|
SCST scst_user interface. The interface is defined by
|
|
scst/include/scst_user.h and documented in doc/scst_user_spec.sgml.
|
|
|
|
Build
|
|
-----
|
|
|
|
From the repository root, "make usr" builds fileio_tgt and stpgd. To build
|
|
only this program, run "make -C usr/fileio". Installation is a separate,
|
|
privileged operation; use the corresponding install target only when system
|
|
installation is intended.
|
|
|
|
Usage
|
|
-----
|
|
|
|
The scst_user kernel module must be loaded before fileio_tgt is started.
|
|
Running fileio_tgt registers live SCST devices and opens every supplied
|
|
backing path. Unless read-only mode is selected, initiators can cause writes
|
|
to those paths. Do not use a real block device or valuable backing file
|
|
without an explicitly prepared test configuration.
|
|
|
|
fileio_tgt [OPTIONS] name path [name path] ...
|
|
|
|
Each name is the SCST device name used by later access-management operations.
|
|
Each path is the backing file or device from which the handler determines the
|
|
virtual device size. Up to the implementation limit, multiple name/path pairs
|
|
can be registered by one process.
|
|
|
|
The following options are supported:
|
|
|
|
- -b, --block=size: block size; it must be a power of two and at least 512
|
|
- -e, --threads=count: number of worker threads
|
|
- -t, --write_through: write-through mode
|
|
- -r, --read_only: read-only mode
|
|
- -o, --direct: open the backing path with O_DIRECT for data I/O
|
|
- -n, --nullio: NULLIO mode; see scst/README for its safety warning
|
|
- -c, --nv_cache: NV_CACHE mode; see scst/README for its semantics
|
|
- -p, --parse=type: "std" (default), "call", or "excpt"
|
|
- -f, --on_free=type: "ignore" (default) or "call"
|
|
- -m, --mem_reuse=type: "all" (default), "read", "write", or "none"
|
|
- -l, --non_blocking: use nonblocking scst_user operations
|
|
- -I, --vdisk_id=ID: virtual disk ID for multi-target setups
|
|
- -F, --flush=n: flush the SGV cache every n seconds
|
|
- -s, --sgv_shared: share the first device's SGV cache
|
|
- -S, --sgv_single_cache=n: use a single-entry SGV cache with n pages
|
|
- -P, --sgv_purge_interval=n: set the SGV purge interval in seconds
|
|
- -u, --unreg_before_close: exercise the obsolete unregister ioctl
|
|
- -D, --sgv_disable_clustered_pool: disable the clustered SGV pool
|
|
- -R, --prealloc_buffers=n: preallocate n buffers
|
|
- -Z, --prealloc_buffer_size=n: preallocated buffer size in KiB
|
|
- -M, --multi_cmd=v: enable or disable multi-command processing (default 1)
|
|
- -v, --version: print the program version
|
|
- -h, --help: print usage information
|
|
|
|
The following options are present only when their corresponding tracing or
|
|
debug feature is compiled in:
|
|
|
|
- -d, --debug=level: tracing level
|
|
- -g, --debug_tm_ignore: enable the DEBUG_TM_IGNORE test feature
|
|
|
|
The current option parser and usage() output in usr/fileio/fileio.c are the
|
|
authoritative command-line reference.
|
|
|
|
Vladislav Bolkhovitin <vst@vlnb.net>, http://scst.sourceforge.net
|