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This patch introduces two more new ioctls to manage atomic updates to file contents -- XFS_IOC_START_COMMIT and XFS_IOC_COMMIT_RANGE. The commit mechanism here is exactly the same as what XFS_IOC_EXCHANGE_RANGE does, but with the additional requirement that file2 cannot have changed since some sampling point. The start-commit ioctl performs the sampling of file attributes. Note: This patch currently samples i_ctime during START_COMMIT and checks that it hasn't changed during COMMIT_RANGE. This isn't entirely safe in kernels prior to 6.12 because ctime only had coarse grained granularity and very fast updates could collide with a COMMIT_RANGE. With the multi-granularity ctime introduced by Jeff Layton, it's now possible to update ctime such that this does not happen. It is critical, then, that this patch must not be backported to any kernel that does not support fine-grained file change timestamps. Signed-off-by: Darrick J. Wong <djwong@kernel.org> Acked-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
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.