f2fs: use inode mutex to keep atomicity of f2fs_falloc

Previously without protection of inode mutex, f2fs_falloc and other data
correlated operations will interfere with each other.
So let's use inode mutex to keep atomicity of f2fs_falloc.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/file.c

@@ -560,6 +560,8 @@ static long f2fs_fallocate(struct file *file, int mode,
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
 		return -EOPNOTSUPP;
 
+	mutex_lock(&inode->i_mutex);
+
 	if (mode & FALLOC_FL_PUNCH_HOLE)
 		ret = punch_hole(inode, offset, len);
 	else
@@ -569,6 +571,9 @@ static long f2fs_fallocate(struct file *file, int mode,
 		inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 		mark_inode_dirty(inode);
 	}
+
+	mutex_unlock(&inode->i_mutex);
+
 	trace_f2fs_fallocate(inode, mode, offset, len, ret);
 	return ret;
 }