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

[Ken'ichi Ohmichi]

Hi,

2007/03/21 16:21:57 -0500, Dave Anderson <anderson at redhat.com> wrote:
>Bob Montgomery wrote:
>
>> On Tue, 2007-03-20 at 11:18 +0900, Ken'ichi Ohmichi wrote:
>> > Hi Bob,
>> >
>> > Thank you for the great report.
>> You are welcome.
>>
>> Before continuing the discussion of issues with proposed changes to ELF
>> dumpfile generation, I'd like to recap where we are and suggest a couple
>> of actions.
>>
>> 1)  Makedumpfile patch:  Ken'ichi Ohmichi's email of Wed, 7 Mar 2007
>> 10:43:38 +0900 contained the patch "point_same_zero_page.patch".  That
>> patch contains the nice solution to remove redundant zero page images
>> from the diskdump dump file by pointing the page descriptors of zero
>> pages to a common zero image.  I suggest that this patch should be
>> applied to makedumpfile as soon as possible, without waiting on a
>> possible solution to the ELF situation.  As described in my report, ELF
>> and diskdump dump files have not shown identical behavior in the past.
>> This patch makes diskdump dump files more accurate, and leaves ELF dump
>> files at the same level of accuracy that they have always had.

I agree with Bob, I will merge the patch "point_same_zero_page.patch" into
a new makedumpfile. But this change is very important, and I want to check
that this change is correct by doing many tests.
I will release a new makedumpfile until the next weekend.


>> With these two patches, crash reports the contents of diskdump dump
>> files produced by makedumpfile correctly.  Zero content pages that have
>> not been excluded for other reasons remain accessible, and pages that
>> have really been excluded become inaccessible, instead of showing 0x0
>> contents.  Crash should continue to read old dump files as before,
>> because of the change in version number in the dumpfiles.
>>
>
>I am a little bit worried that this may cause an
>unnecessary abort -- based upon your experience
>with my suggestion of returning an error instead
>of a zero-filled buffer from the current compressed
>diskdump format -- so I may be paranoid.  Anyway,
>I'll probably put in an "out" so that the user
>has the choice of getting a zero-filled buffer
>like it does now.

I think it is a good idea.


Thanks
Ken'ichi Ohmichi