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7ce31f20a0
Way back when we first implemented FICLONE for XFS, life was simple -- either the the entire remapping completed, or something happened and we had to return an errno explaining what happened. Neither of those ioctls support returning partial results, so it's all or nothing. Then things got complicated when copy_file_range came along, because it actually can return the number of bytes copied, so commit3f68c1f562tried to make it so that we could return a partial result if the REMAP_FILE_CAN_SHORTEN flag is set. This is also how FIDEDUPERANGE can indicate that the kernel performed a partial deduplication. Unfortunately, the logic is wrong if an error stops the remapping and CAN_SHORTEN is not set. Because those callers cannot return partial results, it is an error for ->remap_file_range to return a positive quantity that is less than the @len passed in. Implementations really should be returning a negative errno in this case, because that's what btrfs (which introduced FICLONE{,RANGE}) did. Therefore, ->remap_range implementations cannot silently drop an errno that they might have when the number of bytes remapped is less than the number of bytes requested and CAN_SHORTEN is not set. Found by running generic/562 on a 64k fsblock filesystem and wondering why it reported corrupt files. Cc: <stable@vger.kernel.org> # v4.20 Fixes:3fc9f5e409("xfs: remove xfs_reflink_remap_range") Really-Fixes:3f68c1f562("xfs: support returning partial reflink results") 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 reStructuredText 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.