d16baa3f14
When initializing iocost for a queue, its rqos should be registered before the blkcg policy is activated to allow policy data initiailization to lookup the associated ioc. This unfortunately means that the rqos methods can be called on bios before iocgs are attached to all existing blkgs. While the race is theoretically possible on ioc_rqos_throttle(), it mostly happened in ioc_rqos_merge() due to the difference in how they lookup ioc. The former determines it from the passed in @rqos and then bails before dereferencing iocg if the looked up ioc is disabled, which most likely is the case if initialization is still in progress. The latter looked up ioc by dereferencing the possibly NULL iocg making it a lot more prone to actually triggering the bug. * Make ioc_rqos_merge() use the same method as ioc_rqos_throttle() to look up ioc for consistency. * Make ioc_rqos_throttle() and ioc_rqos_merge() test for NULL iocg before dereferencing it. * Explain the danger of NULL iocgs in blk_iocost_init(). Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jonathan Lemon <bsd@fb.com> Cc: stable@vger.kernel.org # v5.4+ Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.