55e20bd12a
This reverts commit a43a67a2d715540c1368b9501a22b0373b5874c0. This patch reverts the main part of switching direct io implementation to iomap infrastructure. There's a problem in invalidate page that couldn't be solved as regression in this development cycle. The problem occurs when buffered and direct io are mixed, and the ranges overlap. Although this is not recommended, filesystems implement measures or fallbacks to make it somehow work. In this case, fallback to buffered IO would be an option for btrfs (this already happens when direct io is done on compressed data), but the change would be needed in the iomap code, bringing new semantics to other filesystems. Another problem arises when again the buffered and direct ios are mixed, invalidation fails, then -EIO is set on the mapping and fsync will fail, though there's no real error. There have been discussions how to fix that, but revert seems to be the least intrusive option. Link: https://lore.kernel.org/linux-btrfs/20200528192103.xm45qoxqmkw7i5yl@fiona/ 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.