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vfs: enable remap callers that can handle short operations

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Plumb in a remap flag that enables the filesystem remap handler to
shorten remapping requests for callers that can handle it.  Now
copy_file_range can report partial success (in case we run up against
alignment problems, resource limits, etc.).

We also enable CAN_SHORTEN for fideduperange to maintain existing
userspace-visible behavior where xfs/btrfs shorten the dedupe range to
avoid stale post-eof data exposure.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Darrick J. Wong
2018-10-30 10:42:10 +11:00
committed by Dave Chinner
parent df36583619
commit eca3654e3c
4 changed files with 33 additions and 15 deletions
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4
Documentation/filesystems/vfs.txt
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@@ -970,7 +970,9 @@ otherwise noted.
negative error code if errors occurred before any bytes were remapped.
The remap_flags parameter accepts REMAP_FILE_* flags. If
REMAP_FILE_DEDUP is set then the implementation must only remap if the
requested file ranges have identical contents.
requested file ranges have identical contents. If REMAP_CAN_SHORTEN is
set, the caller is ok with the implementation shortening the request
length to satisfy alignment or EOF requirements (or any other reason).
fadvise: possibly called by the fadvise64() system call.