Re: [PATCH v3 4/5] dma/pool: create dma atomic pool only if dma zone has managed pages

[john.p.donnelly@oracle.com]

On 12/13/21 6:27 AM, Baoquan He wrote:
> Currently three dma atomic pools are initialized as long as the relevant
> kernel codes are built in. While in kdump kernel of x86_64, this is not
> right when trying to create atomic_pool_dma, because there's no managed
> pages in DMA zone. In the case, DMA zone only has low 1M memory presented
> and locked down by memblock allocator. So no pages are added into buddy
> of DMA zone. Please check commit f1d4d47c5851 ("x86/setup: Always reserve
> the first 1M of RAM").
> 
> Then in kdump kernel of x86_64, it always prints below failure message:
> 
>   DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
>   swapper/0: page allocation failure: order:5, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
>   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-0.rc5.20210611git929d931f2b40.42.fc35.x86_64 #1
>   Hardware name: Dell Inc. PowerEdge R910/0P658H, BIOS 2.12.0 06/04/2018
>   Call Trace:
>    dump_stack+0x7f/0xa1
>    warn_alloc.cold+0x72/0xd6
>    ? _raw_spin_unlock_irq+0x24/0x40
>    ? __alloc_pages_direct_compact+0x90/0x1b0
>    __alloc_pages_slowpath.constprop.0+0xf29/0xf50
>    ? __cond_resched+0x16/0x50
>    ? prepare_alloc_pages.constprop.0+0x19d/0x1b0
>    __alloc_pages+0x24d/0x2c0
>    ? __dma_atomic_pool_init+0x93/0x93
>    alloc_page_interleave+0x13/0xb0
>    atomic_pool_expand+0x118/0x210
>    ? __dma_atomic_pool_init+0x93/0x93
>    __dma_atomic_pool_init+0x45/0x93
>    dma_atomic_pool_init+0xdb/0x176
>    do_one_initcall+0x67/0x320
>    ? rcu_read_lock_sched_held+0x3f/0x80
>    kernel_init_freeable+0x290/0x2dc
>    ? rest_init+0x24f/0x24f
>    kernel_init+0xa/0x111
>    ret_from_fork+0x22/0x30
>   Mem-Info:
>   ......
>   DMA: failed to allocate 128 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation
>   DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations
> 
> Here, let's check if DMA zone has managed pages, then create atomic_pool_dma
> if yes. Otherwise just skip it.
> 
> Fixes: 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified")
> Cc: stable@vger.kernel.org
> Signed-off-by: Baoquan He <bhe@redhat.com>



  Acked-by: John Donnelly <john.p.donnelly@oracle.com>
  Tested-by:  John Donnelly <john.p.donnelly@oracle.com>


> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: iommu@lists.linux-foundation.org
> ---
>   kernel/dma/pool.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
> index 5a85804b5beb..00df3edd6c5d 100644
> --- a/kernel/dma/pool.c
> +++ b/kernel/dma/pool.c
> @@ -206,7 +206,7 @@ static int __init dma_atomic_pool_init(void)
>   						    GFP_KERNEL);
>   	if (!atomic_pool_kernel)
>   		ret = -ENOMEM;
> -	if (IS_ENABLED(CONFIG_ZONE_DMA)) {
> +	if (has_managed_dma()) {
>   		atomic_pool_dma = __dma_atomic_pool_init(atomic_pool_size,
>   						GFP_KERNEL | GFP_DMA);
>   		if (!atomic_pool_dma)
> @@ -229,7 +229,7 @@ static inline struct gen_pool *dma_guess_pool(struct gen_pool *prev, gfp_t gfp)
>   	if (prev == NULL) {
>   		if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32))
>   			return atomic_pool_dma32;
> -		if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp & GFP_DMA))
> +		if (atomic_pool_dma && (gfp & GFP_DMA))
>   			return atomic_pool_dma;
>   		return atomic_pool_kernel;
>   	}