76c6babc71
[ Upstream commit 336aec7b06be860477be80a4299263a2e9355789 ] Tightening the throttle activation check in blk_throtl_activated() to require both q->td presence and policy bit set introduced a memory leak during disk release: blkg_destroy_all() clears the policy bit first during queue deactivation, causing subsequent blk_throtl_exit() to skip throtl_data cleanup when blk_throtl_activated() fails policy check. Idealy we should avoid modifying blk_throtl_exit() activation check because it's intuitive that blk-throtl start from blk_throtl_init() and end in blk_throtl_exit(). However, call blk_throtl_exit() before blkg_destroy_all() will make a long term deadlock problem easier to trigger[1], hence fix this problem by checking if q->td is NULL from blk_throtl_exit(), and remove policy deactivation as well since it's useless. [1] https://lore.kernel.org/all/CAHj4cs9p9H5yx+ywsb3CMUdbqGPhM+8tuBvhW=9ADiCjAqza9w@mail.gmail.com/#t Fixes: bd9fd5be6bc0 ("blk-throttle: fix access race during throttle policy activation") Reported-by: Yi Zhang <yi.zhang@redhat.com> Closes: https://lore.kernel.org/all/CAHj4cs-p-ZwBEKigBj7T6hQCOo-H68-kVwCrV6ZvRovrr9Z+HA@mail.gmail.com/ Signed-off-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.