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Now that xfs_alloc_vextent() does all the AGF deadlock prevention filtering for multiple allocations in a single transaction, we no longer need the allocation setup code to care about what AGs we might already have locked. Hence we can remove all the "nullfb" conditional logic in places like xfs_bmap_btalloc() and instead have them focus simply on setting up locality constraints. If the allocation fails due to AGF lock filtering in xfs_alloc_vextent, then we just fall back as we normally do to more relaxed allocation constraints. As a result, any allocation that allows AG scanning (i.e. not confined to a single AG) and does not force a worst case full filesystem scan will now be able to attempt allocation from AGs lower than that defined by tp->t_firstblock. This is because xfs_alloc_vextent() allows try-locking of the AGFs and hence enables low space algorithms to at least -try- to get space from AGs lower than the one that we have currently locked and allocated from. This is a significant improvement in the low space allocation algorithm. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Allison Henderson <allison.henderson@oracle.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
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.