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When we're estimating a new speculative preallocation length for an extending write, we should walk backwards through the extent list to determine the number of number of blocks that are physically and logically contiguous with the write offset, and use that as an input to the preallocation size computation. This way, preallocation length is truly measured by the effectiveness of the allocator in giving us contiguous allocations without being influenced by the state of a given extent. This fixes both the problem where ZERO_RANGE within an EOF can reduce preallocation, and prevents the unnecessary shrinkage of preallocation when delalloc extents are turned into unwritten extents. This was found as a regression in xfs/014 after changing delalloc writes to create unwritten extents during writeback. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-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 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.