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Certain workoads that punch holes into speculative preallocation can cause delalloc indirect reservation splits when the delalloc extent is split in two. If further splits occur, an already short-handed extent can be split into two in a manner that leaves zero indirect blocks for one of the two new extents. This occurs because the shortage is large enough that the xfs_bmap_split_indlen() algorithm completely drains the requested indlen of one of the extents before it honors the existing reservation. This ultimately results in a warning from xfs_bmap_del_extent(). This has been observed during file copies of large, sparse files using 'cp --sparse=always.' To avoid this problem, update xfs_bmap_split_indlen() to explicitly apply the reservation shortage fairly between both extents. This smooths out the overall indlen shortage and defers the situation where we end up with a delalloc extent with zero indlen reservation to extreme circumstances. Reported-by: Patrick Dung <mpatdung@gmail.com> Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.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.