Based on previous commit this implements `zfs rewrite -P` flag,
making ZFS to keep blocks logical birth times while rewriting
files. It should exclude the rewritten blocks from incremental
sends, snapshot diffs, etc. Snapshots space usage same time will
reflect the additional space usage from newly allocated blocks.
Since this begins to use new "rewrite" flag in the block pointers,
this commit introduces a new read-compatible per-dataset feature
physical_rewrite. It must be enabled for the command to not fail,
it is activated on first use and deactivated on deletion of the
last affected dataset.
Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alexander Motin <alexander.motin@TrueNAS.com>
Closes#17565
This allows to rewrite content of specified file(s) as-is without
modifications, but at a different location, compression, checksum,
dedup, copies and other parameter values. It is faster than read
plus write, since it does not require data copying to user-space.
It is also faster for sync=always datasets, since without data
modification it does not require ZIL writing. Also since it is
protected by normal range range locks, it can be done under any
other load. Also it does not affect file's modification time or
other properties.
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by: iXsystems, Inc.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Rob Norris <robn@despairlabs.com>
