[PATCH 1/1] mm: Fix struct page layout on 32-bit systems

Christoph Hellwig hch at lst.de
Mon Apr 19 07:34:41 BST 2021


On Fri, Apr 16, 2021 at 04:27:55PM +0100, Matthew Wilcox wrote:
> On Thu, Apr 15, 2021 at 08:08:32PM +0200, Jesper Dangaard Brouer wrote:
> > See below patch.  Where I swap32 the dma address to satisfy
> > page->compound having bit zero cleared. (It is the simplest fix I could
> > come up with).
> 
> I think this is slightly simpler, and as a bonus code that assumes the
> old layout won't compile.

So, why do we even do this crappy overlay of a dma address?  This just
all seems like a giant hack.  Random subsystems should not just steal
a few struct page fields as that just turns into the desasters like the
one we've seen here or probably something worse next time.



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