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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>,
        Anand Jain <anand.jain@oracle.com>,
        David Sterba <dsterba@suse.com>
Subject: [PATCH 4.16 057/110] btrfs: property: Set incompat flag if lzo/zstd compression is set
Date:   Mon, 21 May 2018 23:11:54 +0200
Message-Id: <20180521210510.840166368@linuxfoundation.org>
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4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>

commit 1a63c198ddb810c790101d693c7071cca703b3c7 upstream.

Incompat flag of LZO/ZSTD compression should be set at:

 1. mount time (-o compress/compress-force)
 2. when defrag is done
 3. when property is set

Currently 3. is missing and this commit adds this.

This could lead to a filesystem that uses ZSTD but is not marked as
such. If a kernel without a ZSTD support encounteres a ZSTD compressed
extent, it will handle that but this could be confusing to the user.

Typically the filesystem is mounted with the ZSTD option, but the
discrepancy can arise when a filesystem is never mounted with ZSTD and
then the property on some file is set (and some new extents are
written). A simple mount with -o compress=zstd will fix that up on an
unpatched kernel.

Same goes for LZO, but this has been around for a very long time
(2.6.37) so it's unlikely that a pre-LZO kernel would be used.

Fixes: 5c1aab1dd544 ("btrfs: Add zstd support")
CC: stable@vger.kernel.org # 4.14+
Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add user visible impact ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/props.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -393,6 +393,7 @@ static int prop_compression_apply(struct
 				  const char *value,
 				  size_t len)
 {
+	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	int type;
 
 	if (len == 0) {
@@ -403,14 +404,17 @@ static int prop_compression_apply(struct
 		return 0;
 	}
 
-	if (!strncmp("lzo", value, 3))
+	if (!strncmp("lzo", value, 3)) {
 		type = BTRFS_COMPRESS_LZO;
-	else if (!strncmp("zlib", value, 4))
+		btrfs_set_fs_incompat(fs_info, COMPRESS_LZO);
+	} else if (!strncmp("zlib", value, 4)) {
 		type = BTRFS_COMPRESS_ZLIB;
-	else if (!strncmp("zstd", value, len))
+	} else if (!strncmp("zstd", value, len)) {
 		type = BTRFS_COMPRESS_ZSTD;
-	else
+		btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD);
+	} else {
 		return -EINVAL;
+	}
 
 	BTRFS_I(inode)->flags &= ~BTRFS_INODE_NOCOMPRESS;
 	BTRFS_I(inode)->flags |= BTRFS_INODE_COMPRESS;