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b9b0494017
bcachefs currently populates fiemap data from the extents btree. This works correctly when the fiemap sync flag is provided, but if not, it skips all delalloc extents that have not yet been flushed. This is because delalloc extents from buffered writes are first stored as reservation in the pagecache, and only become resident in the extents btree after writeback completes. Update the fiemap implementation to process holes between extents by scanning pagecache for data, via seek data/hole. If a valid data range is found over a hole in the extent btree, fake up an extent key and flag the extent as delalloc for reporting to userspace. Note that this does not necessarily change behavior for the case where there is dirty pagecache over already written extents, where when in COW mode, writeback will allocate new blocks for the underlying ranges. The existing behavior is consistent with btrfs and it is recommended to use the sync flag for the most up to date extent state from fiemap. Signed-off-by: Brian Foster <bfoster@redhat.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.