xfs: introduce new file range exchange ioctl

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Introduce a new ioctl to handle exchanging ranges of bytes
between files.  The goal here is to perform the exchange atomically with
respect to applications -- either they see the file contents before the
exchange or they see that A-B is now B-A, even if the kernel crashes.

My original goal with all this code was to make it so that online repair
can build a replacement directory or xattr structure in a temporary file
and commit the repair by atomically exchanging all the data blocks
between the two files.  However, I needed a way to test this mechanism
thoroughly, so I've been evolving an ioctl interface since then.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

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Darrick J. Wong 2024-04-15 14:54:14 -07:00

parent 5b9932f600

commit 9a64d9b310

5 changed files with 415 additions and 0 deletions

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1

fs/xfs/Makefile

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41

fs/xfs/libxfs/xfs_fs.h

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339

fs/xfs/xfs_exchrange.c

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30

fs/xfs/xfs_exchrange.h

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4

fs/xfs/xfs_ioctl.c

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