A question about alloc_pages()

Hi,

When alloc_pages() is asked to allocate a block of pages (order > 0), should I be able to expect that page_count(pages[0]) will be 1, and page_count() for all the other pages will be 0?

As far as I can see, nothing in the allocator alters what's in the page count for pages beyond the first when pages are freed, and checks are made that these are 0 upon freeing, so it looks to me like this ought to be the case.

However, I have a report that sometimes this isn't true, and I'm wondering if the allocator can't be relied on in this way, or whether there's a bug somewhere keeping a reference to a released page.

David

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Correct.

Must be a bug.

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Seems I wasn't returning the blocks of pages correctly: the first page needed its page_count() setting to 1 and the an order-N sized page block had to be order-N aligned before calling __free_pages(). However, if you don't turn on CONFIG_DEBUG_VM, it appears to work, but produces some odd effects.

David

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