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Since both committing transaction and writing log-tree are doing plugging on metadata IO, we can unify to use %sync_writers to benefit both cases, instead of checking bio_flags while writing meta blocks of log-tree. We can remove this bio_flags because in order to write dirty blocks, log tree also uses btrfs_write_marked_extents(), inside which we have enabled %sync_writers, therefore, every write goes in a synchronous way, so does checksuming. Please also note that, bio_flags is applied per-context while %sync_writers is applied per-inode, so this might incur some overhead, ie. 1) while log tree is flushing its dirty blocks via btrfs_write_marked_extents(), in which %sync_writers is increased by one. 2) in the meantime, some writeback operations may happen upon btrfs's metadata inode, so these writes go synchronously, too. However, AFAICS, the overhead is not a big one while the win is that we unify the two places that needs synchronous way and remove a special hack/flag. This removes the bio_flags related stuff for writing log-tree. Signed-off-by: Liu Bo <bo.li.liu@oracle.com> Reviewed-by: David Sterba <dsterba@suse.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.