mainlining shenanigans
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> |
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| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
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| Makefile | ||
| 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.