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The compression level is meaningless for lzo, but before commit3f093ccb95("btrfs: harden parsing of compression mount options"), it was silently ignored if passed. After that commit, passing a level with lzo fails to mount: BTRFS error: unrecognized compression value lzo:1 It seems reasonable for users to expect that lzo would permit a numeric level option, as all the other algos do, even though the kernel's implementation of LZO currently only supports a single level. Because it has always worked to pass a level, it seems likely to me that users in the real world are relying on doing so. This patch restores the old behavior, giving "lzo:N" the same semantics as all of the other compression algos. To be clear, silly variants like "lzo:one", "lzo:the_first_option", or "lzo:armageddon" also used to work. This isn't meant to suggest that any possible mis-interpretation of mount options that once worked must continue to work forever. This is an exceptional case where it makes sense to preserve compatibility, both because the mis-interpretation is reasonable, and because nothing tangible is sacrificed. Finally update btrfs_show_options() to ignore the level of LZO, as it is only the default level without any extra meaning. Fixes:3f093ccb95("btrfs: harden parsing of compression mount options") Reviewed-by: Daniel Vacek <neelx@suse.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Calvin Owens <calvin@wbinvd.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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.