f2fs: introduce F2FS_IOC_GET_COMPRESS_BLOCKS

With this newly introduced interface, user can get block
number compression saved in target inode.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -426,6 +426,7 @@ static inline bool __has_cursum_space(struct f2fs_journal *journal,
 #define F2FS_IOC_GET_PIN_FILE		_IOR(F2FS_IOCTL_MAGIC, 14, __u32)
 #define F2FS_IOC_PRECACHE_EXTENTS	_IO(F2FS_IOCTL_MAGIC, 15)
 #define F2FS_IOC_RESIZE_FS		_IOW(F2FS_IOCTL_MAGIC, 16, __u64)
+#define F2FS_IOC_GET_COMPRESS_BLOCKS	_IOR(F2FS_IOCTL_MAGIC, 17, __u64)
 
 #define F2FS_IOC_GET_VOLUME_NAME	FS_IOC_GETFSLABEL
 #define F2FS_IOC_SET_VOLUME_NAME	FS_IOC_SETFSLABEL

fs/f2fs/file.c

@@ -3398,6 +3398,21 @@ static int f2fs_set_volume_name(struct file *filp, unsigned long arg)
 	return err;
 }
 
+static int f2fs_get_compress_blocks(struct file *filp, unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	__u64 blocks;
+
+	if (!f2fs_sb_has_compression(F2FS_I_SB(inode)))
+		return -EOPNOTSUPP;
+
+	if (!f2fs_compressed_file(inode))
+		return -EINVAL;
+
+	blocks = F2FS_I(inode)->i_compr_blocks;
+	return put_user(blocks, (u64 __user *)arg);
+}
+
 long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	if (unlikely(f2fs_cp_error(F2FS_I_SB(file_inode(filp)))))
@@ -3476,6 +3491,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return f2fs_get_volume_name(filp, arg);
 	case F2FS_IOC_SET_VOLUME_NAME:
 		return f2fs_set_volume_name(filp, arg);
+	case F2FS_IOC_GET_COMPRESS_BLOCKS:
+		return f2fs_get_compress_blocks(filp, arg);
 	default:
 		return -ENOTTY;
 	}
@@ -3633,6 +3650,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case FS_IOC_MEASURE_VERITY:
 	case F2FS_IOC_GET_VOLUME_NAME:
 	case F2FS_IOC_SET_VOLUME_NAME:
+	case F2FS_IOC_GET_COMPRESS_BLOCKS:
 		break;
 	default:
 		return -ENOIOCTLCMD;