c891f1fd90
rcu is not used correctly here, because synchronize_rcu() is called
before replacing old value, for example:
remove_and_add_spares // other path
synchronize_rcu
// called before replacing old value
set_bit(RemoveSynchronized)
rcu_read_lock()
rdev = conf->mirros[].rdev
pers->hot_remove_disk
conf->mirros[].rdev = NULL;
if (!test_bit(RemoveSynchronized))
synchronize_rcu
/*
* won't be called, and won't wait
* for concurrent readers to be done.
*/
// access rdev after remove_and_add_spares()
rcu_read_unlock()
Fortunately, there is a separate rcu protection to prevent such rdev
to be freed:
md_kick_rdev_from_array //other path
rcu_read_lock()
rdev = conf->mirros[].rdev
list_del_rcu(&rdev->same_set)
rcu_read_unlock()
/*
* rdev can be removed from conf, but
* rdev won't be freed.
*/
synchronize_rcu()
free rdev
Hence remove this useless flag and prepare to remove rcu protection to
access rdev from 'conf'.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231125081604.3939938-2-yukuai1@huaweicloud.com
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.