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By setting compression for a defrag task, the task will start IO at the end of defrag. After the combo of filemap_flush(), we've already made sure that dirty pages have made progress via async compress thread because the second filemap_flush() will wait for page lock, which won't be unlocked until those pages have been marked as writeback and ordered extents have been queued. And this is for per-inode defrag, it's not helpful to wait on a global %async_delalloc_pages and %nr_async_submits from fs_info. Although waiting on %nr_async_submits means that all bios are submitted down to per-device schedule IO lists, it doesn't wait for their completions, thus users still need to do fsync/sync to make sure the data is on disk. While with this change, it makes sure that pages are marked with writeback bits and will be submitted asynchronously shortly, therefore, the behavior of defrag option '-c' remains unchanged. Signed-off-by: Liu Bo <bo.li.liu@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.