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On Linux the ioctl_ficlonerange() and ioctl_ficlone() system calls are expected to either fully clone the specified range or return an error. The range may be for an entire file. While internally ZFS supports cloning partial ranges there's no way to return the length cloned to the caller so we need to make this all or nothing. As part of this change support for the REMAP_FILE_CAN_SHORTEN flag has been added. When REMAP_FILE_CAN_SHORTEN is set zfs_clone_range() will return a shortened range when encountering pending dirty records. When it's clear zfs_clone_range() will block and wait for the records to be written out allowing the blocks to be cloned. Furthermore, the file range lock is held over the region being cloned to prevent it from being modified while cloning. This doesn't quite provide an atomic semantics since if an error is encountered only a portion of the range may be cloned. This will be converted to an error if REMAP_FILE_CAN_SHORTEN was not provided and returned to the caller. However, the destination file range is left in an undefined state. A test case has been added which exercises this functionality by verifying that `cp --reflink=never|auto|always` works correctly. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #15728 Closes #15842 |
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