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2229276c52
As mentioned in the previous commit, the kernel misuses sb_frextents in the incore mount to reflect both incore reservations made by running transactions as well as the actual count of free rt extents on disk. This results in the superblock being written to the log with an underestimate of the number of rt extents that are marked free in the rtbitmap. Teaching XFS to recompute frextents after log recovery avoids operational problems in the current mount, but it doesn't solve the problem of us writing undercounted frextents which are then recovered by an older kernel that doesn't have that fix. Create an incore percpu counter to mirror the ondisk frextents. This new counter will track transaction reservations and the only time we will touch the incore super counter (i.e the one that gets logged) is when those transactions commit updates to the rt bitmap. This is in contrast to the lazysbcount counters (e.g. fdblocks), where we know that log recovery will always fix any incorrect counter that we log. As a bonus, we only take m_sb_lock at transaction commit time. Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.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.