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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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5
include/linux/fs.h
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@@ -1727,8 +1727,10 @@ struct block_device_operations;
* See Documentation/filesystems/vfs.txt for more details about this call.
*
* REMAP_FILE_DEDUP: only remap if contents identical (i.e. deduplicate)
* REMAP_FILE_CAN_SHORTEN: caller can handle a shortened request
*/
#define REMAP_FILE_DEDUP (1 << 0)
#define REMAP_FILE_CAN_SHORTEN (1 << 1)
/*
* These flags signal that the caller is ok with altering various aspects of
@@ -1736,9 +1738,8 @@ struct block_device_operations;
* implementation; the vfs remap helper functions can take advantage of them.
* Flags in this category exist to preserve the quirky behavior of the hoisted
* btrfs clone/dedupe ioctls.
* There are no flags yet, but subsequent commits will add some.
*/
#define REMAP_FILE_ADVISORY (0)
#define REMAP_FILE_ADVISORY (REMAP_FILE_CAN_SHORTEN)
struct iov_iter;