bcachefs: Fix locking in bch2_ioc_setlabel()

Fixes: 7a254053a590 ("bcachefs: support FS_IOC_SETFSLABEL")
Reported-by: syzbot+7e9efdfec27fbde0141d@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/fs-ioctl.c b/fs/bcachefs/fs-ioctl.c
index aea8132d2c40e585eabd923a9138035f87827455..99c7fe987c74ffa19fa9abe31a479001e9322639 100644 (file)
--- a/fs/bcachefs/fs-ioctl.c
+++ b/fs/bcachefs/fs-ioctl.c
@@ -328,9 +328,8 @@ static int bch2_ioc_setlabel(struct bch_fs *c,
 
        mutex_lock(&c->sb_lock);
        strscpy(c->disk_sb.sb->label, label, BCH_SB_LABEL_SIZE);
-       mutex_unlock(&c->sb_lock);
-
        ret = bch2_write_super(c);
+       mutex_unlock(&c->sb_lock);
 
        mnt_drop_write_file(file);
        return ret;