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https://github.com/kdave/btrfs-progs
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7781d1a2da
Currently, if user specifies value 'no' or 'none' on the command line,
it gets translated to an empty value that is passed to kernel. There was
a change in kernel 5.14 done by commit 5548c8c6f55b ("btrfs: props:
change how empty value is interpreted") that changes the behaviour
in that case.
The empty value is supposed to mean 'the default value' for any
property. For compression there is a need to distinguish resetting the
value and also setting the NOCOMPRESS property. The translation to empty
value makes that impossible.
The explanation and behaviour copied from the kernel patch:
Old behaviour:
$ lsattr file
---------------------- file
# the NOCOMPRESS bit is set
$ btrfs prop set file compression ''
$ lsattr file
---------------------m file
This is equivalent to 'btrfs prop set file compression no' in current
btrfs-progs as the 'no' or 'none' values are translated to an empty
string.
This is where the new behaviour is different: empty string drops the
compression flag (-c) and nocompress (-m):
$ lsattr file
---------------------- file
# No change
$ btrfs prop set file compression ''
$ lsattr file
---------------------- file
$ btrfs prop set file compression lzo
$ lsattr file
--------c------------- file
$ btrfs prop get file compression
compression=lzo
$ btrfs prop set file compression ''
# Reset to the initial state
$ lsattr file
---------------------- file
# Set NOCOMPRESS bit
$ btrfs prop set file compression no
$ lsattr file
---------------------m file
This obviously brings problems with backward compatibility, so this
patch should not be backported without making sure the updated
btrfs-progs are also used and that scripts have been updated to use the
new semantics.
Summary:
- old kernel:
no, none, "" - set NOCOMPRESS bit
- new kernel:
no, none - set NOCOMPRESS bit
"" - drop all compression flags, ie. COMPRESS and NOCOMPRESS
Signed-off-by: Li Zhang <zhanglikernel@gmail.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
91 lines
3.0 KiB
ReStructuredText
91 lines
3.0 KiB
ReStructuredText
btrfs-property(8)
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=================
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SYNOPSIS
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--------
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**btrfs property** <subcommand> <args>
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DESCRIPTION
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-----------
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**btrfs property** is used to get/set/list property for given filesystem object.
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The object can be an inode (file or directory), subvolume or the whole
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filesystem. See the description of **get** subcommand for more information about
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both btrfs object and property.
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***btrfs property** provides an unified and user-friendly method to tune different
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btrfs properties instead of using the traditional method like ``chattr(1)`` or
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``lsattr(1)``.
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SUBCOMMAND
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----------
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get [-t <type>] <object> [<name>]
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get property from a btrfs *object* of given *type*
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A btrfs object, which is set by *object*, can be a btrfs filesystem
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itself, a btrfs subvolume, an inode (file or directory) inside btrfs,
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or a device on which a btrfs exists.
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The option *-t* can be used to explicitly
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specify what type of object you meant. This is only needed when a
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property could be set for more then one object type.
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Possible types are *s[ubvol]*, *f[ilesystem]*, *i[node]* and *d[evice]*, where
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the first lettes is a shortcut.
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Set the name of property by *name*. If no *name* is specified,
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all properties for the given object are printed. *name* is one of
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the following:
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ro
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read-only flag of subvolume: true or false. Please also see section *SUBVOLUME FLAGS*
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in ``btrfs-subvolume(8)`` for possible implications regarding incremental send.
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label
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label of the filesystem. For an unmounted filesystem, provide a path to a block
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device as object. For a mounted filesystem, specify a mount point.
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compression
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compression algorithm set for an inode, possible values: *lzo*, *zlib*, *zstd*.
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To disable compression use *no* or *none*. Empty value resets the
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property and sets a default value.
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.. note::
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This has changed in version 5.18 of btrfs-progs and
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requires kernel 5.14 or newer to work.
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list [-t <type>] <object>
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Lists available properties with their descriptions for the given object.
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See the description of **get** subcommand for the meaning of each option.
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set [-f] [-t <type>] <object> <name> <value>
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Sets a property on a btrfs object.
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See the description of **get** subcommand for the meaning of each option.
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``Options``
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-f
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Force the change. Changing some properties may involve safety checks or
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additional changes that depend on the properties semantics.
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EXIT STATUS
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-----------
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**btrfs property** returns a zero exit status if it succeeds. Non zero is
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returned in case of failure.
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AVAILABILITY
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------------
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**btrfs** is part of btrfs-progs.
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Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for
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further details.
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SEE ALSO
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--------
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``mkfs.btrfs(8)``,
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``lsattr(1)``,
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``chattr(1)``
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