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Kevin Barnett 21a087ceb2 scsi: smartpqi: correct lun reset issues 
[ Upstream commit 2ba55c9851 ]

Problem:
The Linux kernel takes a logical volume offline after a LUN reset.  This is
generally accompanied by this message in the dmesg output:

Device offlined - not ready after error recovery

Root Cause:
The root cause is a "quirk" in the timeout handling in the Linux SCSI
layer. The Linux kernel places a 30-second timeout on most media access
commands (reads and writes) that it send to device drivers.  When a media
access command times out, the Linux kernel goes into error recovery mode
for the LUN that was the target of the command that timed out. Every
command that timed out is kept on a list inside of the Linux kernel to be
retried later. The kernel attempts to recover the command(s) that timed out
by issuing a LUN reset followed by a TEST UNIT READY. If the LUN reset and
TEST UNIT READY commands are successful, the kernel retries the command(s)
that timed out.

Each SCSI command issued by the kernel has a result field associated with
it. This field indicates the final result of the command (success or
error). When a command times out, the kernel places a value in this result
field indicating that the command timed out.

The "quirk" is that after the LUN reset and TEST UNIT READY commands are
completed, the kernel checks each command on the timed-out command list
before retrying it. If the result field is still "timed out", the kernel
treats that command as not having been successfully recovered for a
retry. If the number of commands that are in this state are greater than
two, the kernel takes the LUN offline.

Fix:
When our RAIDStack receives a LUN reset, it simply waits until all
outstanding commands complete. Generally, all of these outstanding commands
complete successfully. Therefore, the fix in the smartpqi driver is to
always set the command result field to indicate success when a request
completes successfully. This normally isn’t necessary because the result
field is always initialized to success when the command is submitted to the
driver. So when the command completes successfully, the result field is
left untouched. But in this case, the kernel changes the result field
behind the driver’s back and then expects the field to be changed by the
driver as the commands that timed-out complete.

Reviewed-by: Dave Carroll <david.carroll@microsemi.com>
Reviewed-by: Scott Teel <scott.teel@microsemi.com>
Signed-off-by: Kevin Barnett <kevin.barnett@microsemi.com>
Signed-off-by: Don Brace <don.brace@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2019-01-26 09:20:49 +01:00
arch x86/topology: Use total_cpus for max logical packages calculation 2019-01-26 09:20:48 +01:00
block block: use rcu_work instead of call_rcu to avoid sleep in softirq 2019-01-22 21:09:57 +01:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: ecc - regularize scalar for scalar multiplication 2019-01-26 09:20:41 +01:00
Documentation x86/speculation/l1tf: Drop the swap storage limit restriction when l1tf=off 2019-01-09 17:45:54 +01:00
drivers scsi: smartpqi: correct lun reset issues 2019-01-26 09:20:49 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs quota: Lock s_umount in exclusive mode for Q_XQUOTA{ON,OFF} quotactls. 2019-01-26 09:20:49 +01:00
include scsi: target/core: Make sure that target_wait_for_sess_cmds() waits long enough 2019-01-26 09:20:45 +01:00
init kbuild: Disable LD_DEAD_CODE_DATA_ELIMINATION with ftrace & GCC <= 4.7 2019-01-22 21:09:54 +01:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel bpf: relax verifier restriction on BPF_MOV | BPF_ALU 2019-01-26 09:20:45 +01:00
lib fix int_sqrt64() for very large numbers 2019-01-22 21:09:55 +01:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm mm: page_mapped: don't assume compound page is huge or THP 2019-01-16 22:03:26 +01:00
net netfilter: ipt_CLUSTERIP: fix deadlock in netns exit routine 2019-01-26 09:20:47 +01:00
samples samples: bpf: fix: error handling regarding kprobe_events 2019-01-26 09:20:42 +01:00
scripts kconfig: fix memory leak when EOF is encountered in quotation 2019-01-26 09:20:46 +01:00
security selinux: always allow mounting submounts 2019-01-26 09:20:42 +01:00
sound ALSA: bebob: fix model-id of unit for Apogee Ensemble 2019-01-26 09:20:49 +01:00
tools perf tools: Add missing open_memstream() prototype for systems lacking it 2019-01-26 09:20:48 +01:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: arm/arm64: vgic: Fix off-by-one bug in vgic_get_irq() 2019-01-09 17:46:04 +01:00
.clang-format page cache: Convert find_get_pages_contig to XArray 2018-10-21 10:46:34 -04:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap mailmap: Update email for Punit Agrawal 2018-11-05 10:02:11 +00:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: update entry for MMP platform 2018-12-03 12:39:57 -08:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-21 14:21:17 -08:00
Makefile kbuild: let fixdep directly write to .*.cmd files 2019-01-26 09:20:43 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 Restructured Text 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.