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[ Upstream commit ddfdd530e43fcb3f7a0a69966e5f6c33497b4ae3 ] While investigating test failures in xfs/17[1-3] in alwayscow mode, I noticed through code inspection that xfs_bmap_alloc_userdata isn't setting XFS_ALLOC_USERDATA when allocating extents for a file's CoW fork. COW staging extents should be flagged as USERDATA, since user data are persisted to these blocks before being remapped into a file. This mis-classification has a few impacts on the behavior of the system. First, the filestreams allocator is supposed to keep allocating from a chosen AG until it runs out of space in that AG. However, it only does that for USERDATA allocations, which means that COW allocations aren't tied to the filestreams AG. Fortunately, few people use filestreams, so nobody's noticed. A more serious problem is that xfs_alloc_ag_vextent_small looks for a buffer to invalidate *if* the USERDATA flag is set and the AG is so full that the allocation had to come from the AGFL because the cntbt is empty. The consequences of not invalidating the buffer are severe -- if the AIL incorrectly checkpoints a buffer that is now being used to store user data, that action will clobber the user's written data. Fix filestreams and yet another data corruption vector by flagging COW allocations as USERDATA. Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com> Acked-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.