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    SubjectRe: [PATCH] Make GFP_DMA allocations w/o ZONE_DMA emit a warning instead of failing
    On Fri, 10 Jun 2011, Russell King - ARM Linux wrote:

    > > We're talking about two different things. Linus is saying that if GFP_DMA
    > > should be a no-op if the hardware doesn't require DMA memory because the
    > > kernel was correctly compiled without CONFIG_ZONE_DMA. I'm asking about a
    > > kernel that was incorrectly compiled without CONFIG_ZONE_DMA and now we're
    > > returning memory from anywhere even though we actually require GFP_DMA.
    > How do you distinguish between the two states? Answer: you can't.

    By my warning which says "enable CONFIG_ZONE_DMA _if_ needed." The
    alternative is to silently return memory from anywhere, which is what the
    page allocator does now, which doesn't seem very user friendly when the
    device randomly works depending on the chance it was actually allocated
    from the DMA mask. If it actually wants DMA and the kernel is compiled
    incorrectly, then I think a single line in the kernel log would be nice to
    point them in the right direction. Users who disable the option usually
    know what they're doing (it's only allowed for CONFIG_EXPERT on x86, for
    example), so I don't think they'll mind the notification and choose to
    ignore it.

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      Last update: 2011-06-11 00:19    [W:0.021 / U:6.960 seconds]
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