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    SubjectRe: [PATCH] lib: Replace calls to __get_free_pages() with __get_dma_pages().
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    On Wed, 2007-06-06 at 03:56 -0400, Robert P. J. Day wrote:
    > On Tue, 5 Jun 2007, Andrew Morton wrote:
    >
    > > On Tue, 5 Jun 2007 16:58:57 -0400 (EDT)
    > > "Robert P. J. Day" <rpjday@mindspring.com> wrote:
    > >
    > > > Replace a couple calls to __get_free_pages() with the corresponding
    > > > calls to __get_dma_pages().
    > > >
    > > > Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
    > > >
    > > > ---
    > > >
    > > > that's the lot of them.
    > > >
    > > > diff --git a/lib/swiotlb.c b/lib/swiotlb.c
    > > > index 10c13ad..8fc38dc 100644
    > > > --- a/lib/swiotlb.c
    > > > +++ b/lib/swiotlb.c
    > > > @@ -201,8 +201,7 @@ swiotlb_late_init_with_default_size(size_t default_size)
    > > > bytes = io_tlb_nslabs << IO_TLB_SHIFT;
    > > >
    > > > while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
    > > > - io_tlb_start = (char *)__get_free_pages(GFP_DMA | __GFP_NOWARN,
    > > > - order);
    > > > + io_tlb_start = (char *)__get_dma_pages(__GFP_NOWARN, order);
    > >
    > > __get_dma_pages() is just pointless obfuscation. I think it'd be better to
    > > go the other way: open-code the GFP_DMA at all callsites then send
    > > __get_dma_pages() bitbucketwards.
    >
    > ok, it's easy enough to put together a patch that rids the tree of the
    > superfluous __get_dma_pages() call. but in converting back to a call
    > to __get_free_pages(), which of the two zone modifiers should be added
    > -- "GFP_DMA" or "__GFP_DMA" -- since they're currently defined
    > equivalently in include/linux/gfp.h. and there's definitely a mixture
    > of usage in the tree at the moment:
    >
    > $ grep -r "get_free.*GFP_DMA" *
    > arch/s390/kernel/smp.c: __get_free_pages(GFP_KERNEL | GFP_DMA,
    > drivers/net/arm/ep93xx_eth.c: page = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
    > drivers/net/arm/ep93xx_eth.c: page = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
    > drivers/s390/net/qeth_main.c: ptr = (void *) __get_free_page(GFP_KERNEL|GFP_DMA);
    > drivers/s390/net/claw.c: (void *)__get_free_pages(__GFP_DMA,
    > drivers/s390/net/claw.c: (void *)__get_free_pages(__GFP_DMA,
    > drivers/s390/net/claw.c: p_buff=(void *)__get_free_pages(__GFP_DMA,
    > drivers/s390/net/claw.c: (void *)__get_free_pages(__GFP_DMA,
    > drivers/s390/net/claw.c: p_buff = (void *)__get_free_pages(__GFP_DMA,
    > drivers/s390/block/dasd.c: device->ccw_mem = (void *) __get_free_pages(GFP_ATOMIC | GFP_DMA, 1);
    > drivers/s390/char/tty3270.c: __get_free_pages(GFP_KERNEL|GFP_DMA, 0);
    > drivers/s390/char/sclp_cpi.c: sccb = (struct cpi_sccb *) __get_free_page(GFP_KERNEL | GFP_DMA);
    > drivers/s390/cio/cmf.c: mem = (void*)__get_free_pages(GFP_KERNEL | GFP_DMA,
    > include/linux/gfp.h: __get_free_pages((gfp_mask) | GFP_DMA,(order))
    > lib/swiotlb.c: io_tlb_start = (char *)__get_free_pages(GFP_DMA | __GFP_NOWARN,
    > lib/swiotlb.c: io_tlb_overflow_buffer = (void *)__get_free_pages(GFP_DMA,
    >
    > i'm guessing "GFP_DMA" would be the right choice, which means that,
    > for consistency, the calls using __GFP_DMA should be switched over as
    > well. guidance, anyone?

    FWIW I prefer:

    GFP_KERNEL | __GFP_DMA
    GFP_ATOMIC | __GFP_DMA

    and

    GFP_DMA

    That is, when used as a modifier use __GFP_, when used as a class use
    GFP_.

    -
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