On Sun, Mar 01, 2020 at 04:05:13PM -0800, David Rientjes wrote:
> The single atomic pool is allocated from the lowest zone possible since
> it is guaranteed to be applicable for any DMA allocation.
>
> Devices may allocate through the DMA API but not have a strict reliance
> on GFP_DMA memory. Since the atomic pool will be used for all
> non-blockable allocations, returning all memory from ZONE_DMA may
> unnecessarily deplete the zone.
>
> Provision for multiple atomic pools that will map to the optimal gfp
> mask of the device. These will be wired up in a subsequent patch.
>
> Signed-off-by: David Rientjes <[email protected]>
> ---
> kernel/dma/remap.c | 75 +++++++++++++++++++++++++++-------------------
> 1 file changed, 45 insertions(+), 30 deletions(-)
>
> diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
> --- a/kernel/dma/remap.c
> +++ b/kernel/dma/remap.c
> @@ -100,6 +100,8 @@ void dma_common_free_remap(void *cpu_addr, size_t size)
>
> #ifdef CONFIG_DMA_DIRECT_REMAP
> static struct gen_pool *atomic_pool __ro_after_init;
> +static struct gen_pool *atomic_pool_dma32 __ro_after_init;
> +static struct gen_pool *atomic_pool_normal __ro_after_init;
Maybe rename atomic_pool as well as it really kinda looks like the
default at the moment?
>
> #define DEFAULT_DMA_COHERENT_POOL_SIZE SZ_256K
> static size_t atomic_pool_size __initdata = DEFAULT_DMA_COHERENT_POOL_SIZE;
> @@ -111,66 +113,79 @@ static int __init early_coherent_pool(char *p)
> }
> early_param("coherent_pool", early_coherent_pool);
>
> -static gfp_t dma_atomic_pool_gfp(void)
> +static int __init __dma_atomic_pool_init(struct gen_pool **pool,
> + size_t pool_size, gfp_t gfp)
> {
Can this just return the pool and return NULL (or an ERR_PTR) on
failure?
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