Re: Problem with ISO9660 and files stored on multiple extents

[Carlo Caione]

On Thu, Feb 16, 2017 at 12:32 PM, Thomas Schmitt <address@hidden> wrote:
> Hi,
>
> Carlo Caione wrote:
>> > I think that the problem
>> > here is that endless.squash has been stored in two extents in the
>> > ISO9660 and GRUB doesn't deal fine with that (also according to this
>> > comment
>> > http://git.savannah.gnu.org/cgit/grub.git/tree/grub-core/fs/iso9660.c#n960
>
> Andrei Borzenkov wrote:
>> This comment could be stale and misleading.
>
> The code of read_node() in iso9660.c looks ready for multi-extent (aka ISO
> level 3).
>
> I have a very densely compressed test ISO for large file support
>    http://scdbackup.webframe.org/large.iso.bz2
> which bunzip2 inflates from 4.5 KiB to 4+ GiB.

Yeah, I made some more tests and apparently the problem is not in the
ISO9660 module but in the SQUASH4 module.
To be perfectly honest I have already a patch that solves my problem
but I'm having a hard time to understand WHY it solves the issue since
I'm still not really familiar with squashfs (I casually found it
during my debugging).
Of course probably it is only masking a problem somewhere else. Still digging.

diff --git a/grub-core/fs/squash4.c b/grub-core/fs/squash4.c
index b97b344..4fef813 100644
--- a/grub-core/fs/squash4.c
+++ b/grub-core/fs/squash4.c
@@ -895,7 +895,7 @@ grub_squash_read_data (struct grub_squash_data *data,
       break;
     }

-  if (fragment == 0xffffffff)
+  if (fragment == 0xffffffff || fragment == 0)
     return direct_read (data, ino, off, buf, len);

   err = read_chunk (data, &frag, sizeof (frag),

-- 
Carlo Caione  |  +39.340.80.30.096  |  Endless