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Tony Battersby c7bd85a7b9 scsi: qla2xxx: target: Add back SRR support 
Background: loading qla2xxx with "ql2xtgt_tape_enable=1" enables
Sequence Level Error Recovery (SLER), which is most commonly used for
tape drives.  With SLER enabled, if there is a recoverable I/O error
during a SCSI command, a Sequence Retransmission Request (SRR) will be
used to retry the I/O at a low-level completely within the driver
without propagating the error to the upper levels of the SCSI stack.

SRR support was removed in 2017 by commit 2c39b5ca2a ("qla2xxx: Remove
SRR code"). Add it back, new and improved.

The old removed SRR code used sequence numbers to correlate the SRR
CTIOs with SRR immediate notify messages.  I don't see how that would
work reliably with MSI-X interrupts and multiple queues.  So instead use
the exchange address to find the command associated with the immediate
notify (qlt_srr_to_cmd).

The old removed SRR code had a function qlt_check_srr_debug() to
simulate a SRR, but it didn't work for me.  Instead I just used fiber
optic attenuators attached to the FC cable to reduce the strength of the
signal and induce errors.  Unfortunately this only worked for inducing
SRRs on Data-Out (write) commands, so that is all I was able to test.

The code to build a new scatterlist for a SRR with nonzero offset has
been improved to reduce memory requirements and has been well-tested.
However it does not support protection information.

When a single cmd gets multiple SRRs, the old removed SRR code would
restore the data buffer from the values in cmd->se_cmd before processing
the new SRR.  That might be needed if the offset for the new SRR was
lower than the offset for the previous SRR, but I am not sure if that
can happen.  In my testing, when a single cmd gets multiple SRRs, the
SRR offset always increases or stays the same.  But in case it can
decrease, I added the function qlt_restore_orig_sg().  If this is not
supposed to happen then qlt_restore_orig_sg() can be removed to simplify
the code.

I ran into some HBA firmware bugs with QLE269x, QLE27xx, and QLE28xx
firmware 9.05.xx - 9.08.xx where a SRR would cause the HBA to misbehave
badly.  Since SRRs are rare and therefore difficult to test, I figured
it would be worth checking for the buggy firmware and disabling SLER
with a warning instead of letting others run into the same problem on
the rare occasion that they get a SRR.  This turned out to be difficult
because the firmware version isn't known in the normal NVRAM config
routine, so I added a second NVRAM config routine that is called after
the firmware version is known.

Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Link: https://patch.msgid.link/654b7181-b79e-40ed-a15b-6d6e441a5d5f@cybernetics.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
2025-11-12 18:17:28 -05:00
arch Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
block block-6.18-20251009 2025-10-10 10:37:13 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push contains the following changes: 2025-10-10 08:56:16 -07:00
Documentation RTC for 6.18 2025-10-11 11:56:47 -07:00
drivers scsi: qla2xxx: target: Add back SRR support 2025-11-12 18:17:28 -05:00
fs - Avoid -Wflex-array-member-not-at-end warnings 2025-10-10 14:06:02 -07:00
include Revert "i2c: boardinfo: Annotate code used in init phase only" 2025-10-11 23:57:33 +02:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/zcrx: increment fallback loop src offset 2025-10-08 07:26:14 -06:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel tracing fixes for v6.18: 2025-10-11 16:06:04 -07:00
lib lib/test_kho: use kho_preserve_vmalloc instead of storing addresses in fdt 2025-10-07 13:48:56 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab hotfix for 6.18-rc1 2025-10-11 10:40:24 -07:00
net bpf-fixes 2025-10-11 10:31:38 -07:00
rust 7 hotfixes. All 7 are cc:stable and all 7 are for MM. 2025-10-11 10:14:55 -07:00
samples Char/Misc/IIO/Binder changes for 6.18-rc1 2025-10-04 16:26:32 -07:00
scripts Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
security integrity-v6.18 2025-10-05 10:48:33 -07:00
sound sound fixes for 6.18-rc1 2025-10-10 09:55:19 -07:00
tools - Remove a bunch of asm implementing condition flags testing in KVM's 2025-10-11 11:19:16 -07:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt hyperv-next for v6.18 2025-10-07 08:40:15 -07:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap MAINTAINERS, .mailmap: update Umang's email address 2025-10-07 13:48:55 -07:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB/Thunderbolt changes for 6.18-rc1 2025-10-04 16:07:08 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Just one series here - Mike Rappoport has taught KEXEC handover to 2025-10-11 10:27:52 -07:00
Makefile Linux 6.18-rc1 2025-10-12 13:42:36 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.