ec39f7696c
Async CRCs and compression submit IO through helper threads, which means they have IO priority inversions when cgroup IO controllers are in use. This flags all of the writes submitted by btrfs helper threads as REQ_CGROUP_PUNT. submit_bio() will punt these to dedicated per-blkcg work items to avoid the priority inversion. For the compression code, we take a reference on the wbc's blkg css and pass it down to the async workers. For the async CRCs, the bio already has the correct css, we just need to tell the block layer to use REQ_CGROUP_PUNT. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Chris Mason <clm@fb.com> Modified-and-reviewed-by: Tejun Heo <tj@kernel.org> 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.