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[ Upstream commit125bfc7cd7] /sys/block/[device]/queue/iostats is used to control whether to count io stat. Write 0 to it will clear queue_flags QUEUE_FLAG_IO_STAT which means iostats is disabled. If we disable iostats and later endable it, the io issued during this period will be counted incorrectly, inflight will be decreased to -1. //T1 set iostats echo 0 > /sys/block/md0/queue/iostats clear QUEUE_FLAG_IO_STAT //T2 issue io if (QUEUE_FLAG_IO_STAT) -> false bio_start_io_acct inflight++ echo 1 > /sys/block/md0/queue/iostats set QUEUE_FLAG_IO_STAT //T3 io end if (QUEUE_FLAG_IO_STAT) -> true bio_end_io_acct inflight-- -> -1 Also, if iostats is enabled while issuing io but disabled while io end, inflight will never be decreased. Fix it by checking start_time when io end. If start_time is not 0, call bio_end_io_acct(). Fixes:528bc2cf2f("md/raid10: enable io accounting") Signed-off-by: Li Nan <linan122@huawei.com> Signed-off-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20230609094320.2397604-1-linan666@huaweicloud.com 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 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.