kernel BUG at page_alloc.c:85 (iounmap)

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I have a driver which calls marks a physical page as PG_Reserved, calls
ioremap_nocache() on it, performs a non-destructive memory write, and then
calls iounmap(). I have a recurring problem which I can't figure out. After
28 such map/unmap calls, I get an error in page_alloc.c on line 85. This is
with 2.4.0-test2. The offending line is in function __free_pages_ok:

        if (page->buffers)
                BUG();

My guess is that the page I'm trying to map with iounmap() has a non-zero value
of buffers before I map it, but ioremap() doesn't care about that. But when I
go to iounmap it, then it checks buffers and complains.

Is this correct? And if so, what does 'buffers' do?

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Timur Tabi - ttabi@interactivesi.com
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