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All reads bio that go through btrfs_map_bio need to be completed in user context. And read I/Os are the most common and timing critical in almost any file system workloads. Embed a work_struct into struct btrfs_bio and use it to complete all read bios submitted through btrfs_map, using the REQ_META flag to decide which workqueue they are placed on. This removes the need for a separate 128 byte allocation (typically rounded up to 192 bytes by slab) for all reads with a size increase of 24 bytes for struct btrfs_bio. Future patches will reorganize struct btrfs_bio to make use of this extra space for writes as well. (All sizes are based a on typical 64-bit non-debug build) Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Christoph Hellwig <hch@lst.de> 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 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.