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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>
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.