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Qu Wenruo
1e17738d6b
Unlike the iomap_folio_state structure, the btrfs_subpage structure has a lot of extra sub-bitmaps, namely: - writeback sub-bitmap - locked sub-bitmap iomap_folio_state uses an atomic for writeback tracking, while it has no per-block locked tracking. This is because iomap always locks a single folio, and submits dirty blocks with that folio locked. But btrfs has async delalloc ranges (for compression), which are queued with their range locked, until the compression is done, then marks the involved range writeback and unlocked. This means a range can be unlocked and marked writeback at seemingly random timing, thus it needs the extra tracking. This needs a huge rework on the lifespan of async delalloc range before we can remove/simplify these two sub-bitmaps. - ordered sub-bitmap - checked sub-bitmap These are for COW-fixup, but as I mentioned in the past, the COW-fixup is not really needed anymore and these two flags are already marked deprecated, and will be removed in the near future after comprehensive tests. Add related comments to indicate we're actively trying to align the sub-bitmaps to the iomap ones. Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@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 reStructuredText 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.