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Currently the defrag ioctl cannot rewrite the extents without
compression. Add a new flag for that, as setting compression to 0 (or
"no compression") means to do no changes to compression so take what is
the current default, like mount options or properties.
The defrag setting overrides mount or properties. The compression
BTRFS_DEFRAG_DONT_COMPRESS is only used for in-memory operations and
does not need to have a fixed value.
Mount with zstd:9, copy test file from /usr/bin/ (about 260KB):
$ mount -o compress=zstd:9 /dev/vda /mnt
$ filefrag -vsb testfile
filefrag: -b needs a blocksize option, assuming 1024-byte blocks.
Filesystem type is: 9123683e
File size of testfile is 297704 (292 blocks of 1024 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 127: 13312.. 13439: 128: encoded
1: 128.. 255: 13364.. 13491: 128: 13440: encoded
2: 256.. 291: 13424.. 13459: 36: 13492: last,encoded,eof
testfile: 3 extents found
$ compsize testfile
Processed 1 file, 3 regular extents (3 refs), 0 inline, 1 fragments.
Type Perc Disk Usage Uncompressed Referenced
TOTAL 42% 124K 292K 292K
zstd 42% 124K 292K 292K
Defrag to uncompressed:
$ btrfs fi defrag --nocomp testfile
$ filefrag -vsb testfile
filefrag: -b needs a blocksize option, assuming 1024-byte blocks.
Filesystem type is: 9123683e
File size of testfile is 297704 (292 blocks of 1024 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 291: 291840.. 292131: 292: last,eof
testfile: 1 extent found
$ compsize testfile
Processed 1 file, 1 regular extents (1 refs), 0 inline, 1 fragments.
Type Perc Disk Usage Uncompressed Referenced
TOTAL 100% 292K 292K 292K
none 100% 292K 292K 292K
Compress again with LZO:
$ btrfs fi defrag -clzo testfile
$ filefrag -vsb testfile
filefrag: -b needs a blocksize option, assuming 1024-byte blocks.
Filesystem type is: 9123683e
File size of testfile is 297704 (292 blocks of 1024 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 127: 13312.. 13439: 128: encoded
1: 128.. 255: 13392.. 13519: 128: 13440: encoded
2: 256.. 291: 13480.. 13515: 36: 13520: last,encoded,eof
testfile: 3 extents found
$ compsize testfile
Processed 1 file, 3 regular extents (3 refs), 0 inline, 1 fragments.
Type Perc Disk Usage Uncompressed Referenced
TOTAL 64% 188K 292K 292K
lzo 64% 188K 292K 292K
Signed-off-by: David Sterba <dsterba@suse.com>