Am Thu, 18 May 2017 04:37:20 +0000
schrieb Atsushi Kumagai <ats-kumagai at wm.jp.nec.com>:
> Hello Zaslonko,
>
> > When re-filtering the dump file after the free pages have already been
> > stripped out we get an error "Can't get necessary symbols for excluding
> > free pages" if newly specified dump level is below 16 (preserves free
> > pages).
> > According to the code, the check for the new dump level is done BEFORE
> > the new dump level is actually set (based on the dump level specified in
> > the command and the one from the input dump file).
> > Moving the new_dump_level calculation ahead would fix the error.
>
> Well, I guess the real problem is different.
> The error you said is printed by exclude_free_page():
>
> if ((SYMBOL(node_data) == NOT_FOUND_SYMBOL)
> && (SYMBOL(pgdat_list) == NOT_FOUND_SYMBOL)
> && (SYMBOL(contig_page_data) == NOT_FOUND_SYMBOL)) {
> ERRMSG("Can't get necessary symbols for excluding free pages.\n");
> return FALSE;
> }
>
> I think the availability of these symbols are not related to free pages.
> exclude_free_page() is called if info->page_is_buddy is null, I estimate that
> this situation occurs only if the kernel is older(2.6.16 or before).
>
> However, I don't think you use such too old kernel, so I suspect that
> setup_page_is_buddy() should be updated for newer kernel.
Mikhail is on vacation now - so I try to explain:
The test case is as follows:
1) We have a -d31 filtered dump "dump.d31"
2) We want to compress the dump with "makedumpfile -c dump.31 dump31.compressed"
This fails with:
makedumpfile -c dump.31 dump.31.compressed
Excluding unnecessary pages : [100.0 %]
exclude_free_page: Can't get necessary symbols for excluding free pages.
dump_level is changed to 31, because dump.31 was created by dump_level(31).
makedumpfile Failed.
The problem is that setup_page_is_buddy() is not called in this case because
info->dump_level is still 0 since it was not adjusted early enough:
if (info->dump_level & DL_EXCLUDE_FREE)
setup_page_is_buddy();
Because it is not set info->page_is_buddy is NULL and therefore the following
if condition gets true:
if ((info->dump_level & DL_EXCLUDE_FREE) && !info->page_is_buddy)
if (!exclude_free_page(cycle))
return FALSE;
Since we don't have the symbols in VMCOREINFO (and IMHO don't need it?) the
exclude_free_page() functions fails with the described error message.
So our fix is to adjust the info->level before setup_page_is_buddy() is called.
Best Regards
Michael
> Could you tell me your kernel version and how to reproduce this issue ?
