Re: [PATCH] btrfs: skip compression property for anything other than files and dirs

[David Sterba <dsterba@suse.cz>]

On Thu, Apr 21, 2022 at 11:01:22AM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> The compression property only has effect on regular files and directories
> (so that it's propagated to files and subdirectories created inside a
> directory). For any other inode type (symlink, fifo, device, socket),
> it's pointless to set the compression property because it does nothing
> and ends up unnecessarily wasting leaf space due to the pointless xattr
> (75 or 76 bytes, depending on the compression value). Symlinks in
> particular are very common (for example, I have almost 10k symlinks under
> /etc, /usr and /var alone) and therefore it's worth to avoid wasting
> leaf space with the compression xattr.
> 
> For example, the compression property can end up on a symlink or character
> device implicitly, through inheritance from a parent directory
> 
>   $ mkdir /mnt/testdir
>   $ btrfs property set /mnt/testdir compression lzo
> 
>   $ ln -s yadayada /mnt/testdir/lnk
>   $ mknod /mnt/testdir/dev c 0 0
> 
> Or explicitly like this:
> 
>   $ ln -s yadayda /mnt/lnk
>   $ setfattr -h -n btrfs.compression -v lzo /mnt/lnk
> 
> So skip the compression property on inodes that are neither a regular
> file nor a directory.
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

Added to misc-next, thanks.