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xfs_buftarg_drain() is called from xfs_log_quiesce() to ensure the buffer cache is reclaimed during unmount. xfs_log_quiesce() is also called from xfs_quiesce_attr(), however, which means that cache state is completely drained for filesystem freeze and read-only remount. While technically harmless, this is unnecessarily heavyweight. Both freeze and read-only mounts allow reads and thus allow population of the buffer cache. Therefore, the transitional sequence in either case really only needs to quiesce outstanding writes to return the filesystem in a generally read-only state. Additionally, some users have reported that attempts to freeze a filesystem concurrent with a read-heavy workload causes the freeze process to stall for a significant amount of time. This occurs because, as mentioned above, the read workload repopulates the buffer LRU while the freeze task attempts to drain it. To improve this situation, replace the drain in xfs_log_quiesce() with a buffer I/O quiesce and lift the drain into the unmount path. This removes buffer LRU reclaim from freeze and read-only [re]mount, but ensures the LRU is still drained before the filesystem unmounts. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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.