Bug#756619: apt-get update: SIGBUS when run out of disk space

[Jakub Wilk <jwilk@debian.org>]

* Julian Andres Klode <jak@jak-linux.org>, 2014-08-01, 19:57:
> > # apt-get update
> > Hit http://ftp.debian.org unstable InRelease
> > Hit http://ftp.debian.org unstable/main amd64 Packages/DiffIndex
> > Bus error (core dumped). 60%
>
> I just wonder how this happens. APT is writing to an mmap. That mmap 
> has been allocated on the disk already, so it should not fail, unless 
> the FS lied and has no space anymore, despite having promised it to 
> APT, or am I wrong?

How does apt allocate the space? In the DynamicMMap constructor I see:

     Fd->Seek(WorkSpace - 1);
     char C = 0;
     Fd->Write(&C,sizeof(C));

which would create just a sparse file. Maybe posix_fallocate(3) is 
needed instead?

(But I'm not familiar with apt codebase, so maybe I'm looking at the 
completely wrong place.)

--
Jakub Wilk