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As mentioned in the previous commit, online repair wants to allocate space to write out a new metadata structure, and it also wants to hedge against system crashes during repairs by logging (and later cancelling) EFIs to free the space if we crash before committing the new data structure. Therefore, create a trio of functions to schedule automatic reaping of freshly allocated unwritten space. xfs_alloc_schedule_autoreap creates a paused EFI representing the space we just allocated. Once the allocations are made and the autoreaps scheduled, we can start writing to disk. If the writes succeed, xfs_alloc_cancel_autoreap marks the EFI work items as stale and unpauses the pending deferred work item. Assuming that's done in the same transaction that commits the new structure into the filesystem, we guarantee that either the new object is fully visible, or that all the space gets reclaimed. If the writes succeed but only part of an extent was used, repair must call the same _cancel_autoreap function to kill the first EFI and then log a new EFI to free the unused space. The first EFI is already committed, so it cannot be changed. For full extents that aren't used, xfs_alloc_commit_autoreap will unpause the EFI, which results in the space being freed during the next _defer_finish cycle. Signed-off-by: Darrick J. Wong <djwong@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 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.