Gleb Chesnokov
60ff16ef4f
Found by manual code inspection, not by an analyzer or a runtime test.
When scst_suspend_activity() times out with commands still active,
__scst_resume_activity() revives the command and management counters.
The old wrapper calls percpu_ref_reinit(), whose zero-count requirement
is enforced by this kernel assertion:
WARN_ON_ONCE(!percpu_ref_is_zero(ref));
Upstream 3.18-4.19 and the retained EL7/UEK4/UEK5 implementations preserve
the per-CPU allocation and use long counters, but reinit still rejects
this legitimate nonzero resurrection. Restore the initial reference
additively, retain outstanding references, and restore per-CPU operation
with the kernel's bias, counter clearing and release-store ordering.
Keep explicitly forced atomic mode unchanged.
SCST serializes kill and resurrection with scst_suspend_mutex and keeps
both counters alive even when their release callbacks run. Require the
same external serialization for mode changes and exit. Concurrent gets
and puts remain allowed.
Kill confirmation can wake the caller before confirm_switch is cleared.
Drain a pending switch callback with rcu_barrier_sched() before reusing
the counters. The kernel switch waitqueue is private, and older kernels
do not export percpu_ref_switch_to_percpu(). This conditional barrier
can also wait for unrelated RCU callbacks; it is skipped once the switch
has completed. Native resurrection on 4.20+ and EL8+ remains unchanged.
Add scst-LIB-percpu-ref to scst.ko with private, real kernel counters.
Keep the backport helper available to KUnit on modern kernels, using
their counter layout and unified RCU API. Cover immediate resurrection
with active refs, resurrection after draining, forced atomic mode, and
repeated suspend cancellations with commands completing while dead.
Also fix the fake Kbuild cleaner used by the Python tooling tests.
CI reported test_cleanup_without_packaged_tooling failing with
"find: cannot delete .../isert-scst.ko: No such file or directory".
iSCSI cleans kernel/ and kernel/isert-scst/ concurrently, so one fixture
find can remove an artifact after the other has enumerated it. Use
-ignore_readdir_race to tolerate only vanished files, matching Kbuild's
idempotent rm -f behavior. Keep other find errors and the injected
FAIL_CLEAN failure fatal; retain parallel cleanup and artifact checks.
Tests, builds and VM validation were not run, as requested.
Overview
This is the source code repository of the SCST project. SCST is a collection of Linux kernel drivers that implement SCSI target functionality. The SCST project includes:
- The SCST core in the scst/ subdirectory.
- A tool for loading, saving and modifying the SCST configuration in directory scstadmin/.
- Several SCSI target drivers in the directories iscsi-scst/, qla2x00t-32gbit/, qla2x00t/, srpt/, scst_local/ and fcst/.
- User space programs in the usr/ subdirectory, e.g. fileio_tgt.
- Various documentation in the doc/ subdirectory.
Documentation
- Building and installing SCST.
- Build options: Clang, cross-compilation, and kernel module signing.
- Configuration and administration: targets, devices,
LUNs, and
/etc/scst.conf. - Core and device handlers: operating modes, module parameters, and sysfs configuration.
- Target drivers: iSCSI, iSER, QLogic Fibre Channel, SRP, FCoE, and local loopback.
- Performance tuning.
- Clustered persistent reservations: synchronization through DLM.
- T10 protection information: data integrity modes and configuration.
- Developer references: architecture and userspace handler interface (SGML sources), and sysfs interface rules.
- Contributing: code style, commit conventions, local checks, and guides to KUnit and component testing.
Current master packages
Prebuilt x86_64 packages from the latest successfully published master
build are available in the rolling
master-rpm prerelease.
These are development snapshots, not SCST releases.
The snapshot contains RPM bundles for selected Rocky Linux and Oracle Linux
UEK kernels. It also contains Ubuntu LTS bundles with scst-dkms, scstadmin
and iscsi-scst binary packages and their Debian source package files. Exact
distribution releases and RPM kernel versions are included in the asset names.
Every .tar.gz bundle has a matching .sha256 file. The complete snapshot is
replaced after each successful package workflow for the current master
commit.
QLogic target driver
Two QLogic target drivers are included in the SCST project.
The default driver is located in the qla2x00t-32gbit directory. It is the newer one.
May anyone wish to switch back to the older driver that only supported up to
16 Gb/s adapters, it is located in qla2x00t directory. To make use of the
older driver build scst with environment variable QLA_32GBIT=no set.
Vladislav Bolkhovitin vst@vlnb.net, http://scst.sourceforge.net
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