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Now that we've converted xfs_reflink_remap_extent to use the new xfs_trans_alloc_inode API, we can focus on its slightly unusual behavior with regard to quota reservations. Since it's valid to remap written blocks into a hole, we must be able to increase the quota count by the number of blocks in the mapping. However, the incore space reservation process requires us to supply an asymptotic guess before we can gain exclusive access to resources. We'd like to reserve all the quota we need up front, but we also don't want to fail a written -> allocated remap operation unnecessarily. The solution is to make the remap_extents function call the transaction allocation function twice. The first time we ask to reserve enough space and quota to handle the absolute worst case situation, but if that fails, we can fall back to the old strategy: ask for the bare minimum space reservation upfront and increase the quota reservation later if we need to. Later in this patchset we change the transaction and quota code to try to reclaim space if we cannot reserve free space or quota. Restructuring the remap_extent function in this manner means that if the fallback increase fails, we can pass that back to the caller knowing that the transaction allocation already tried freeing space. Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Brian Foster <bfoster@redhat.com> 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.