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The writeback delalloc conversion code is racy with respect to changes in the currently cached file mapping. This stems from the fact that the bmapi allocation code requires a file range to allocate and the writeback conversion code assumes the range of the currently cached mapping is still valid with respect to the fork. It may not be valid, however, because the ilock is cycled (potentially multiple times) between the time the cached mapping was populated and the delalloc conversion occurs. To facilitate a solution to this problem, create a new xfs_bmapi_delalloc() wrapper to xfs_bmapi_write() that takes a file (FSB) offset and attempts to allocate whatever delalloc extent backs the offset. Use a new bmapi flag to cause xfs_bmapi_write() to set the range based on the extent backing the bno parameter unless bno lands in a hole. If bno does land in a hole, fall back to the current behavior (which may result in an error or quietly skipping holes in the specified range depending on other parameters). This patch does not change behavior. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.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.