[Crash-utility] handling missing kdump pages in diskdump format

[Vivek Goyal]

On Thu, Mar 01, 2007 at 09:15:05PM +0900, Ken'ichi Ohmichi wrote:
> 
> (added Vivek Goyal)
> (added redhat-kexec-kdump-ml)
> 
> Hi everyone,
> 
> If Bob's proposal (the end of this mail) is merged into makedumpfile,
> the analysis behavior of ELF dumpfile is different from kdump-compressed
> dumpfile's as follows.
> When reading ELF dumpfile, the crash utility treats the excluded pages
> as zero-filled pages. But, as to kdump-compressed dumpfile, the crash
> utility will display the warning message to mean "These pages are
> excluded by partial dump" when it accesses the excluded pages.
> 

I quickly went through this thread. I don't know much about the diskdump
format but from a layman's perspective, instead of keeping the zero pages
and compressing them, why not extend diskdump format and maintain another
bitmap which signifies the valid zero pages but they are not physically 
part of the core file? I think overall it might reduce dump size.

Secondly, for ELF format core files, probably we can disable the behavior of
excluding zero filled pages from dumpfile and then "crash" behavior can
be consistent. (Return zero filled page only for valid data otherwise crib).

Thanks
Vivek