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When sorting the block group list for reclaim we are using a block group's used bytes counter without taking the block group's spinlock, so we can race with a concurrent task updating it (at btrfs_update_block_group()), which makes tools like KCSAN unhappy and report a race. Since the sorting is not strictly needed from a functional perspective and such races should rarely cause any ordering changes (only load/store tearing could cause them), not to mention that after the sorting the ordering may no longer be accurate due to concurrent allocations and deallocations of extents in a block group, annotate the accesses to the used counter with data_race() to silence KCSAN and similar tools. Reviewed-by: Qu Wenruo <wqu@suse.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.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 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.