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Before this patch, for read-write array: 1) md_check_recover() found that something need to be done, and it'll try to grab 'reconfig_mutex'. The case that md_check_recover() need to do something: - array is not suspend; - super_block need to be updated; - 'MD_RECOVERY_NEEDED' or 'MD_RECOVERY_DONE' is set; - unusual case related to safemode; 2) if 'MD_RECOVERY_RUNNING' is not set, and 'MD_RECOVERY_NEEDED' is set, md_check_recover() will try to choose a sync action, and then queue a work md_start_sync(). 3) md_start_sync() register sync_thread; After this patch, 1) is the same; 2) if 'MD_RECOVERY_RUNNING' is not set, and 'MD_RECOVERY_NEEDED' is set, queue a work md_start_sync() directly; 3) md_start_sync() will try to choose a sync action, and then register sync_thread(); Because 'MD_RECOVERY_RUNNING' is cleared when sync_thread is done, 2) and 3) and md_do_sync() is always ran in serial and they can never concurrent, this change should not introduce any behavior change for now. Also fix a problem that md_start_sync() can clear 'MD_RECOVERY_RUNNING' without protection in error path, which might affect the logical in md_check_recovery(). The advantage to change this is that array reconfiguration is independent from daemon now, and it'll be much easier to synchronize it with io, consider that io may rely on daemon thread to be done. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Xiao Ni <xni@redhat.com> Signed-off-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20230825031622.1530464-4-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.