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b54bb86556
When flushing delalloc, in COW mode at cow_file_range(), before entering the loop that allocates extents and creates ordered extents, we do a call to btrfs_drop_extent_map_range() for the whole range. This is pointless because in the loop we call create_io_em(), which will also call btrfs_drop_extent_map_range() before inserting the new extent map. So remove that call at cow_file_range() not only because it is not needed, but also because it will make the btrfs_drop_extent_map_range() calls made from create_io_em() waste time searching the extent map tree, and that tree can be large for files with many extents. It also makes us waste time at btrfs_drop_extent_map_range() allocating and freeing the split extent maps for nothing. 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.