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[BACKGROUND] Btrfs has a lot of different bi_end_io functions, to handle different raid profiles. But they introduced a lot of different contexts for btrfs_bio::end_io() calls: - Simple read bios Run in task context, backed by either endio_meta_workers or endio_workers. - Simple write bios Run in IRQ context. - RAID56 write or rebuild bios Run in task context, backed by rmw_workers. - Mirrored write bios Run in irq context. This is inconsistent, and contributes to the number of workqueues used in btrfs. [ENHANCEMENT] Make all the above bios call their btrfs_bio::end_io() in task context, backed by either endio_meta_workers for metadata, or endio_workers for data. For simple write bios, merge the handling into simple_end_io_work(). For mirrored write bios, it will be a little more complex, since both the original or the cloned bios can run the final btrfs_bio::end_io(). Here we make sure the cloned bios are using btrfs_bioset, to reuse the end_io_work, and run both original and cloned work inside the workqueue. Add extra ASSERT()s to make sure btrfs_bio_end_io() is running in task context. This not only unifies the context for btrfs_bio::end_io() functions, but also opens a new door for further btrfs_bio::end_io() related cleanups. Signed-off-by: Qu Wenruo <wqu@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.