hfs: fix return value of hfs_get_block()

Direct writes to empty inodes fail with EIO.  The generic direct-io code
is in part to blame (a patch has been submitted as "direct-io: allow
direct writes to empty inodes"), but hfs is worse affected than the other
filesystems because the fallback to buffered I/O doesn't happen.

The problem is the return value of hfs_get_block() when called with
!create.  Change it to be more consistent with the other modules.

Link: http://lkml.kernel.org/r/4538ab8c35ea37338490525f0f24cbc37227528c.1539195310.git.ernesto.mnd.fernandez@gmail.comSigned-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Reviewed-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hfs/extent.c

@@ -345,7 +345,9 @@ int hfs_get_block(struct inode *inode, sector_t block,
 	ablock = (u32)block / HFS_SB(sb)->fs_div;
 
 	if (block >= HFS_I(inode)->fs_blocks) {
-		if (block > HFS_I(inode)->fs_blocks || !create)
+		if (!create)
+			return 0;
+		if (block > HFS_I(inode)->fs_blocks)
 			return -EIO;
 		if (ablock >= HFS_I(inode)->alloc_blocks) {
 			res = hfs_extend_file(inode);