From 5548c8c6f55bf0097075b3720e14857e3272429f Mon Sep 17 00:00:00 2001 From: David Sterba Date: Mon, 14 Jun 2021 18:10:04 +0200 Subject: [PATCH] btrfs: props: change how empty value is interpreted Based on user feedback and actual problems with compression property, there's no support to unset any compression options, or to force no compression flag. Note: This has changed recently in e2fsprogs 1.46.2, 'chattr +m' (setting NOCOMPRESS). In btrfs properties, the empty value should really mean reset to defaults, for all properties in general. Right now there's only the compression one, so this change should not cause too many problems. 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: David Sterba --- fs/btrfs/props.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c index a17e53e..b1cb5a8 100644 --- a/fs/btrfs/props.c +++ b/fs/btrfs/props.c @@ -260,6 +260,10 @@ static int prop_compression_validate(const char *value, size_t len) if (btrfs_compress_is_valid_type(value, len)) return 0; + if ((len == 2 && strncmp("no", value, 2) == 0) || + (len == 4 && strncmp("none", value, 4) == 0)) + return 0; + return -EINVAL; } @@ -269,7 +273,17 @@ static int prop_compression_apply(struct inode *inode, const char *value, struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); int type; + /* Reset to defaults */ if (len == 0) { + BTRFS_I(inode)->flags &= ~BTRFS_INODE_COMPRESS; + BTRFS_I(inode)->flags &= ~BTRFS_INODE_NOCOMPRESS; + BTRFS_I(inode)->prop_compress = BTRFS_COMPRESS_NONE; + return 0; + } + + /* Set NOCOMPRESS flag */ + if ((len == 2 && strncmp("no", value, 2) == 0) || + (len == 4 && strncmp("none", value, 4) == 0)) { BTRFS_I(inode)->flags |= BTRFS_INODE_NOCOMPRESS; BTRFS_I(inode)->flags &= ~BTRFS_INODE_COMPRESS; BTRFS_I(inode)->prop_compress = BTRFS_COMPRESS_NONE; -- 2.7.4