[PATCH] btrfs: fix chattr failing on nodatasum files that have the compress flag

[Hengyu Liang <hengyul@cs.unc.edu>]

Commit cf1afec09e9f ("btrfs: validate properties before setting them")
made btrfs_set_prop() validate a property before setting it. For the
compression property, the validation fails with -EINVAL when the inode
has NODATASUM.

However, a file created on a filesystem mounted with nodatasum has
NODATASUM and still inherits the compress flag from its directory, and
btrfs_fileattr_set() sets the compression property whenever the new
flags include FS_COMPR_FL. As of now, chattr fails on such a file, even
when it only changes another flag.

The issue can be reproduced with:

    mkfs.btrfs -f /dev/sdb
    mount -o nodatasum /dev/sdb /mnt
    mkdir /mnt/dir
    chattr +c /mnt/dir
    touch /mnt/dir/file
    chattr +A /mnt/dir/file

Before commit cf1afec09e9f ("btrfs: validate properties before setting
them"), the last command succeeds.

After that commit, it fails with EINVAL.

This patch will make btrfs_fileattr_set() set the compression property
only when the inode can be compressed.

Fixes: cf1afec09e9f ("btrfs: validate properties before setting them")
Cc: stable@vger.kernel.org # 7.2+
Signed-off-by: Hengyu Liang <hengyul@cs.unc.edu>
---
 fs/btrfs/ioctl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 52aab510aea0..347509043f2e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -421,7 +421,12 @@ int btrfs_fileattr_set(struct mnt_idmap *idmap,
 	if (IS_ERR(trans))
 		return PTR_ERR(trans);
 
-	if (comp) {
+	/*
+	 * An inode with NODATASUM can not be compressed but can still have the
+	 * compress flag, inherited from its parent directory. Setting the
+	 * property fails validation for such an inode, so leave it unset.
+	 */
+	if (comp && btrfs_inode_can_compress(inode)) {
 		ret = btrfs_set_prop(trans, inode, "btrfs.compression",
 				     comp, strlen(comp), 0);
 		if (ret)
-- 
2.53.0