Re: [PATCH]Fix: Init page count for all pages during higher order allocs

[ebiederm@xmission.com (Eric W. Biederman)]

Suparna Bhattacharya <suparna@in.ibm.com> writes:

> The call to set_page_count(page, 1) in page_alloc.c appears to happen 
> only for the first page, for order 1 and higher allocations.
> This leaves the count for the rest of the pages in that block 
> uninitialised.

Actually it should be zero.

This is deliberate because high order pages should not be referenced by
their partial pages.  It might make sense to add a PG_large flag and
then in the immediately following struct page add a pointer to the next
page, so you can identify these pages by inspection.  Doing something
similar to the PG_skip flag.

Beyond that I get nervous, that people will treat it as endorsement of
doing a high order continuous allocation and then fragmenting the page.

Eric
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