f2fs: allow compression of files without blocks

Files created by truncate(1) have a size but no blocks, so
they can be allowed to enable compression.

Signed-off-by: Chao Liu <liuchao@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -1879,7 +1879,7 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
 		if (iflags & F2FS_COMPR_FL) {
 			if (!f2fs_may_compress(inode))
 				return -EINVAL;
-			if (S_ISREG(inode->i_mode) && inode->i_size)
+			if (S_ISREG(inode->i_mode) && F2FS_HAS_BLOCKS(inode))
 				return -EINVAL;
 
 			set_compress_context(inode);