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When starting a defrag, we should update the writeback index of the inode's mapping in case it currently has a value beyond the start of the range we are defragging. This can help performance and often result in getting less extents after writeback - for e.g., if the current value of the writeback index sits somewhere in the middle of a range that gets dirty by the defrag, then after writeback we can get two smaller extents instead of a single, larger extent. We used to have this before the refactoring in 5.16, but it was removed without any reason to do so. Originally it was added in kernel 3.1, by commit2a0f7f5769("Btrfs: fix recursive auto-defrag"), in order to fix a loop with autodefrag resulting in dirtying and writing pages over and over, but some testing on current code did not show that happening, at least with the test described in that commit. So add back the behaviour, as at the very least it is a nice to have optimization. Fixes:7b508037d4("btrfs: defrag: use defrag_one_cluster() to implement btrfs_defrag_file()") CC: stable@vger.kernel.org # 5.16 Signed-off-by: Filipe Manana <fdmanana@suse.com> 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.